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Review

Recent Advancements in P-Type Inorganic Semiconductor Thin-Film Transistors: A Review

by
Narendranaik Mude
,
Jongsu Lee
and
Sungwoon Cho
*
Department of Advanced Components and Materials Engineering, Sunchon National University, Suncheon 57922, Republic of Korea
*
Author to whom correspondence should be addressed.
Crystals 2025, 15(4), 341; https://doi.org/10.3390/cryst15040341
Submission received: 11 March 2025 / Revised: 26 March 2025 / Accepted: 1 April 2025 / Published: 3 April 2025
(This article belongs to the Special Issue Solution Processing and Properties of Oxide Films and Nanostructures)
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Abstract

:
The continuous growth of energy-efficient electronic devices and compact systems has motivated researchers to develop TFTs based on p-type semiconductors. This review examines the developments in p-type thin-film transistors (TFTs) processed using solution methods to achieve integration with complementary metal–oxide–semiconductor technology. Improving organic p-type materials is critical for achieving advanced mobility and stability characteristics with suitable process integration. Scientists study these materials for use in wearable devices which display mechanical strength when fitted onto a curve. This review presents an exclusive discussion about the wide spectrum of applications which involve flexible displays and sensors, together with upcoming technologies such as artificial skin and flexible integrated circuits. The article examines present material challenges, along with device reliability and large-scale production methods, to give a thorough analysis of solution-processed p-type TFTs toward their broad implementation in upcoming electronic devices. By summarizing the developments and most recent studies in the field, this review aims to provide useful information regarding current research into and future trends of p-type TFTs.

1. Introduction

Oxide semiconductors exhibit considerable potential for use in flexible and transparent electronic applications, including transparent displays, sensor arrays, flexible solar cells, and neuromorphic and integrated circuits [1,2,3]. Oxide-based thin-film transistors (TFTs) have been established as sustainable solutions for display technologies. For example, amorphous In-Ga-Zn-O, with a mobility of 10 cm2/V·s, has been utilized for the fabrication of next-generation flexible and flat-panel displays [4]. However, despite the existence of several high-performance n-type transparent oxide semiconductors, a p-type oxide with comparable performance is yet to be discovered. Oxide semiconductor materials, which exhibit similar or better performance, can not only enhance display technologies but also introduce advances in transparent electronics and display technologies. Modern industries require flexible electronic solutions because electronic components are being integrated across multiple fields. Today’s electronics depend on TFTs, which execute essential device operations such as switching, amplification, and signal processing. Among TFTs, p-channel TFTs are particularly significant because of their ability to control the positive-charge carriers (holes) within the transistor channel. However, because native hole killers such as oxygen vacancies (VO) have relatively low formation energies, they are easier to generate, which further annihilates the holes and creates harsh conditions for p-type characteristics [5,6]. Consequently, it is challenging to fabricate high-performance p-type oxide semiconductors with acceptable doping levels.
In the modern era, flexible electronics has emerged as a new form of smart technology that can be applied in wearable health-monitoring devices, rollable displays, etc. [7,8,9]. TFTs are critical components of these devices. However, the current methods for fabricating TFTs include evaporation [10,11,12,13], atomic layer deposition [14], and magnetron sputtering [15], which are not compatible with flexible-substrate manufacturing because of their rigid processing conditions and high cost. Various approaches have been undertaken to address this issue, including ultraviolet (UV) treatment [16], combustion synthesis, sol–gel on-chip synthesis, and carbon-free aqueous synthesis. Solution processing demonstrates great potential as a fabrication method for producing TFTs on flexible substrates. The solution processing technique enables functional material deposition through liquid solutions, which benefits production through low-temperature operation while working with flexible substrates, along with scalability [17,18]. Solution-processable TFTs have recently been highlighted because of their potential to address the issues of vacuum-processing methods and pave the way for the fabrication of low-weight, flexible, and even-band stretchable electronics [19,20]. Hence, the solution processing of TFTs is a breakthrough in the field of flexible electronics, introducing new possibilities for the creation of new devices.
This review explores solution-processed p-type thin-film transistors (TFTs) and their potential integration into complementary metal–oxide–semiconductor (CMOS) technology. This research examines advanced organic p-type materials that deliver better mobility while ensuring stability and compatibility for integration into flexible wearable electronics. This research explores the applications of flexible displays with sensors while discussing emerging technologies including artificial skin technologies. This review evaluates material performance issues together with device stability concerns and large-scale manufacturing obstacles to present prospects on using p-type TFTs in advanced electronic systems.

2. P-Type Semiconductor Materials

To date, a handful of p-type semiconductors such as CuxO, SnO, NiO, and delafossite CuMO2 (M = Al and Gr) have successfully been incorporated into TFTs as channel components. As shown in Figure 1a, copper oxide in the form of cuprous oxide or cuprite (Cu2O) and cupric oxide or tenorite (CuO), which exhibit p-type characteristics, originates from negatively charged Cu vacancies and possibly interstitial oxygen as acceptor defects [21,22,23]. Synthesis of Cu2O occurs via chemical reduction combined with thermal oxidation and electrochemical deposition. Synthesis techniques provide exact measurements of particle dimensions, along with morphology control, to match the requirements of its numerous applications. The solid crystalline form of Cu2O adopts a cubic arrangement in its crystal structure. A direct bandgap of 2.137 eV makes Cu2O a suitable material for photovoltaic applications, especially optoelectronic applications, which benefit from its superior photoconductive properties. Metal oxide crystals, such as CuO, exist as monoclinic crystals. The material has a bandgap of 1.2 eV and operates as a p-type semiconductor [21,23]. The excellent catalytic properties coupled with stability of the CuO material recommend it for industrial utilization. The extensive use of CuO extends to ceramic production followed by its application as an electrode component in batteries and components for chemical sensors and chemical catalysts. The chemical properties of CuO aid in various industrial processes which involve harmful reaction cleanup along with chemical reduction and oxidation.
Tin oxide includes both intrinsic (n-type semiconductor) tin dioxide (SnO2) and tin monoxide (SnO), as shown Figure 1b. SnO2 can be synthesized using methods such as chemical vapor deposition (CVD), sputtering, sol–gel processes, and hydrothermal synthesis. These methods impact the material’s surface area, crystalline structure, and electrical properties. SnO2 exists as a rutile crystal arrangement. This material exists as an n-type semiconductor because it has a large band gap, which reaches 3.6 eV. Its optical transparence, together with electrical conductivity, make SnO2 stand out as a material. The chemical industry uses transformable SnO2 in two applications: in ceramics, where it also serves as an active catalyst, and in transparent conductive surfaces for displays and solar cells. Due to its high optical and electrical characteristics, SnO2 functions well for both gas sensor applications and lithium-ion battery electrode applications. The solid compound SnO had a tetragonal crystal structure. The electrical properties of this material are affected by the mixing between O–2p and Sn–5s levels, which occurs at the top of the valence band in SnO [24]. This material shows no water solubility, together with reduction characteristics. The reduced form of tin oxide functions both as a ceramic material and as a reducing agent in chemical procedures. The specific properties of this compound make it useful for advanced materials science applications.
The p-type nickel oxide semiconductor material exists in the form of NiO and at the energy level of oxide [25,26]. The band structure of NiO was reported by Lany et al. [27], as shown in Figure 1c, and it provides necessary insights into its electronic characteristics. Different fabrication techniques, such as thermal decomposition, sol–gel processes, hydrothermal synthesis, and electrochemical deposition, can be used to synthesize NiO. The methods modify both the stoichiometric makeup and crystalline characteristics of the material. NiO exists as a crystalline solid which adopts a rock salt crystal structure. A non-stoichiometric effect exists in NiO crystals, leading to a Ni:O ratio that differs from 1:1. The semiconductor behavior of NiO shows p-type characteristics because it possesses a bandgap of 3.6 eV [28,29,30,31,32,33]. NiO is used in ceramics, as an electrode material in batteries and fuel cells, and as a catalyst in different chemical reactions. It is also used in the production of electrochromic devices with sensors and magnetic materials. The compound NiO exhibits superb electronic properties, together with stability elements, which make it essential for diverse energy storage and conversion systems. The electronic and optical properties and catalytic behavior of copper oxide, along with tin oxide and nickel oxide materials, suit them for various electronic and optical and catalytic applications. Different devices utilize their distinct band gaps together with semiconductor behavior to determine their operational performance.
Crystals 15 00341 g001
Figure 1. (a) Ionic bond formed between a closed-shell cation and oxide ion. Cu2O defects: schematic showing vacancies and interstitials. Reproduced with permission from [21]. Copyright 2010, Applied Physics Letters. (b) Band structure of SnO. Reproduced with permission from [24]. Copyright 2010, Applied Physics Letters. (c) Band structure of NiO and O-rich and Ni-rich defect diagrams. Reproduced with permission from [26]. Copyright 2020 WILEY-VCH.
Figure 1. (a) Ionic bond formed between a closed-shell cation and oxide ion. Cu2O defects: schematic showing vacancies and interstitials. Reproduced with permission from [21]. Copyright 2010, Applied Physics Letters. (b) Band structure of SnO. Reproduced with permission from [24]. Copyright 2010, Applied Physics Letters. (c) Band structure of NiO and O-rich and Ni-rich defect diagrams. Reproduced with permission from [26]. Copyright 2020 WILEY-VCH.
Crystals 15 00341 g001
Deposition methods including vacuum and solution processes have been used to fabricate TFTs. Traditional methods for fabricating TFTs, including physical vapor deposition and CVD, are not suitable for flexible substrates because of their rigid processing conditions and high costs. Various techniques have been developed to overcome this challenge, including solution processing, UV treatment, combustion synthesis, sol–gel processes, and carbon-free aqueous methods [34,35,36,37,38,39,40,41,42,43,44,45,46]. Pasquarelli et al. reported different deposition techniques for solution processing [47]; these are presented in Figure 2. Solution-based deposition facilitates the fabrication of p-channel TFTs with several important benefits when compared with those fabricated using traditional approaches. The production of flexible-substrate TFTs can become cost-efficient using reproducible processing via various techniques applicable to soluble solutions, including spin coating, chemical bath, dip coating, doctor blade and metering rod usage, slot casting, spray coating, screen printing, injection printing, and aerosol jet technology. Flexible electronic devices that serve different practical purposes can be fabricated by integrating them into various wearable and foldable displays.

3. Advancements in P-Type Semiconductor Devices

3.1. P-Type TFTs by Solution Process

Improvements in p-type materials have led to the creation of innovative materials and composites for flexible devices that require superior electrical performance and stability. In 2021, Mude et al. prepared copper tin sulfide (CTS) TFTs using a solution process [48]. In their study, CTS thin films were integrated into TFTs using a solution process by varying the concentration of the CTS precursor solution. The solution-processed CTS TFTs with high performance at low voltages exhibited p-type conduction with excellent stability. The viscosity and thickness of the CTS films increased with increasing CTS concentration. Thermogravimetric analysis and differential thermal analysis (TG–DTA) were performed at 180–210 °C, and the results showed a dihydroxylation reaction caused by the evaporation of the remaining organic residues and inorganic by-products, as shown in Figure 3a. P-channel CTS TFTs with a mobility of 2.43 cm2/V·s and excellent stability under a negative bias stress are suitable for low-power electronic devices.
In 2021, Mude et al. introduced solution-processed amorphous p-channel copper–tin–sulfur–gallium oxide (CTSGO) thin-film transistors (TFTs), which achieved the highest performance when treated with UV/O3 photocuring [49]. Their material properties, together with device performance, received significant improvement through this method, which positions CTSGO as a leading candidate for future electronic applications. The UV/O3 treated p-channel CTSGO TFT device demonstrated a field effect mobility (μFE) at 1.75 ± 0.15 cm2 V−1 s−1, together with an on/off current ratio (ION/IOFF) of ~104 when operated at −5 V, as shown in Figure 3b. CTSGO proves suitable for CMOS circuits and displays along with other optoelectronic devices because it operates with high speed and minimal power requirements [49]. The promising future of CTSGO TFTs depends on solving stability challenges from environmental factors, together with improving fabrication process optimization for practical use.
In 2020, Cheng et al. developed amorphous p-type CuNiSnO (a-CNTO) TFTs processed at low temperatures [50], which advanced the field of oxide semiconductors. When deposited at 100 °C, the a-CNTO films produced transistors with promising electrical traits suitable for use in flexible and transparent electronics. Their smooth surface exhibited a root-mean-square roughness of 0.25 nm and retained approximately 85% visible-light transmission, as shown in Figure 3c. The p-type a-CNTO TFTs exhibited a current ratio of 1.2 × 105 between the ON and OFF states, along with a threshold voltage of −2.3 V and μFE of 1.37 cm2/V·s [50]. Although the progress in p-type a-CNTO TFTs has demonstrated promise, their performance still falls short of that of n-type TFTs, mainly because of the off-state current level and reliability concerns. Additional research is required to improve these materials for their successful implementation in CMOS applications.

3.2. Improvement in Organic P-Type Materials

Organic materials receive improved properties through mobility enhancement, which extends their device operational period through tailored material structures. Their enhanced performance capabilities create possibilities for including these materials into flexible transparent systems. In 2018, Wijeyasinghe et al. introduced a method of p-doping Copper(I) Thiocyanate (CuSCN), which represents notable progress as it leads to superior operational capabilities of hole-transport layers (HTLs) in transistors and organic solar cells (OSCs) [51]. The electronic properties and stability of CuSCN receive improvements through three different doping methods that utilize C60F48, solvent-induced copper vacancies and chlorine doping. These methods have demonstrated substantial improvements in hole mobility, power conversion efficiency, and overall device stability. This method shifts the Fermi energy towards the valence band, resulting in a tenfold increase in hole mobility (up to 0.18 cm2 V⁻1 s⁻1) and enhanced bias stress stability in transistors, as shown in Figure 4a. Power conversion efficiencies exceeded 19.10% when using DMSO/DMF mixtures because the mixtures created more copper vacancies, which reduced Fermi level impedance and increased conductivity [51]. When doped with Cl2, the performance of CuSCN reached levels equivalent to traditional HTLs and proved effective for both OSCs and PSCs. Modern p-doping methods generate better transistor operations through superior hole mobility while maintaining stable bias stress conditions. Transformation of CuSCN layers through doping procedures enables higher power conversion efficiency and improved alignment with photoactive substances to boost device output.
In 2023, Lu et al. demonstrated that water-only inks made from carbon nanotubes, graphene, and nanocellulose can generate sufficient all-carbon thin-film transistors (TFTs) by achieving a maximum temperature of 70 °C, all while avoiding the use of dangerous chemicals [52]. Sun-powered electronics reach an important milestone through the development of all-carbon thin-film transistors (TFTs) which use water-only printing techniques. The novel approach combines green materials and processes to remove the necessity of dangerous solvents while performing low-temperature operations as shown in Figure 4b. The creation of these transistors depends on carbon nanotubes (CNTs), graphene, and crystalline nanocellulose (CNC) in aqueous inks to enable aerosol jet printing at low temperatures. An ink solution based on water enables companies to create environmentally friendly production practices which reduce their dependence on dangerous chemicals [52]. The implementation of TFTs in different flexible electronic devices brings increased value to consumer electronics and sensors applications. Computational research demonstrates a successful integration of electronic applications using devices which provide both high on/off ratios along with exceptional mobility characteristics. The current developments promise good results, but the printing process must overcome the remaining difficulties to achieve a reliable film density together with good adhesion. Device performance could receive additional enhancement through the incorporation of 2D materials apart from carbon-based materials.
In 2017, Petti et al. fabricated flexible thin-film transistors with integrated inverters using solution-processed p-type CuSCN [53]. CuSCN is the primary material used to fabricate flexible TFTs with integrated inverter circuits owing to its specialized features that combine solution-based fabrication techniques. The hooks used for hole transport provide the TFTs with the ability to work at reduced voltage levels suitable for flexible electronic applications. CuSCN-based TFTs receive sufficient power from a voltage of 2.0 V because of their strong electric-double-layer gate capacitance. The recorded average mobility measurements for bottom-gate and top-gate configurations are 0.0016 cm2/V·s and 0.013 cm2/V·s, respectively. The transistor functionality of CuSCN remains active after the device is bent to a radius of 4 mm because of its mechanical toughness. Flexible substrates integrated with CuSCN can be used to produce unipolar NOT logic gates, which achieve a voltage gain of 3.4 when operated at low voltages, as shown in Figure 4c. The combination of AlOx with passivation layers enhances hole mobility to 0.008 cm2/V·s [53,54,55]. Researchers have investigated different solutions for CuSCN to improve its potential for use in organic electronic applications. The potential of CuSCN for low-voltage operation is high; however, its performance needs further development to match the current n-type semiconductor benchmarks.

3.3. Integration of Flexible Devices

P-type semiconductors are essential components of foldable electronics owing to their excellent hole transport properties. The progress in material and device processing in flexible electronics is of significant interest in the fields of flexible displays, wearable electronics, photovoltaics, and sensors. In 2017, Liu et al. fabricated p-type Cu:NiO thin films for transparent electronics and low-temperature applications [56]. As shown in Figure 5a, solution–combustion synthesis (SCS) facilitates the low-temperature fabrication of p-type Cu:NiO thin films to produce inexpensive and high-quality oxide semiconductors for target applications in fields such as transparent electronics. The development of low-temperature–processed Cu thin films through SCS offers a viable method for producing low-cost, flexible p-type oxide electronics and represents a significant advancement in the development of CMOS circuits. The Cu5% NiO TFTs exhibited exceptional electrical performances in transparent electronics. p-channel TFTs are highly suitable for driving light-emitting diodes (LEDs) because of their bottom-hole-injection electrode structures. To prove this concept, a prototype green-light LED pixel circuit was constructed by connecting a TFT source terminal to an LED, which allowed a wide range of modulations of the LED light emission intensity, demonstrating the excellent control capability of the p-type TFTs.
Another approach is the development of a flexible device. Recently, in 2018, Yang et al. reported a p-type Li:NiOx active semiconductor for high-performance electronics and low-temperature combustion synthesis [57]. Figure 5b shows a schematic of the low-temperature combustion synthesis and UV treatment used to fabricate the high-performance p-type Li:NiOx fabricated for real-world electronics applications. A high transmittance exceeding 80% was observed. A low-temperature method combining SCS and deep-UV irradiation was proposed to prepare p-type Li-doped NiOx (Li:NiOx) thin films at 150 °C for high-performance electronics. The prepared Li:NiOx TFTs exhibited high mobilities and low fabrication temperatures.
In 2023, Wu et al. reported flexible and transparent p-type copper iodide (CuI) TFTs [58]. CuI is a promising material for flexible and transparent electronics, with a threshold voltage of 0.35 V, μFE of 60 cm2/V·s, and Ion/Ioff of 103. The high-performance characteristics of CuI-based TFTs, such as their high mobility, transparency, and flexibility (Figure 5c), make them suitable for high-level applications. The results of this study create possibilities for future developments that will lead to flexible display technologies and low-power electronics.
In 2024, Kim et al. reported that controlled 2D growth via atomic layer deposition (ALD) significantly enhances the stability and performance of flexible SnO thin-film transistors (TFTs) [59]. The improved performance of SnO TFTs resulted from optimized deposition practices, which produced higher mobility, as better film quality was achieved, along with a reduction in structural defects. The controlled growth protocol enabled the fabrication of TFT devices with a low subthreshold swing, facilitating the implementation of energy-efficient devices. Interlayers made from hafnium dioxide or aluminum-doped titanium dioxide played a significant role in reducing oxygen-related defects, which improved the bias stress stability of the devices. Further investigations are needed to enhance these fabrication methods for wider adoption in flexible electronic systems. In addition, representative performance results of the state-of-the-art p-type TFTs reported to date are summarized in Table 1.

3.4. Application of P-Type Thin-Film Transistors

As shown in Figure 6, p-type semiconductor materials in flexible electronics have been utilized in various application fields. Flexible printed sensors containing solution-processed p-channel TFTs have been employed in numerous applications for various monitoring and control purposes, such as environmental monitoring, industrial monitoring, and automotive sensing. These sensors can measure parameters such as pressure, strain, chemical retardants, and biometric signals and can thus be used in various sensing contexts in different fields [75,76,77]. Radio-frequency identification (RFID) in flexible electronics for smart packaging allows for the creation of cost-effective thin metallic tags that can be easily incorporated into numerous products and materials. Flexible RFID tags are useful in product packaging, smart clothing, intelligent labeling, and inventory tracking. They can also handle stresses such as bending and folding and can hence be used in logistics, retailing, and healthcare. In addition, their durability and flexibility improve their capacity to handle the flow of items in places where normal rigid RFID tags do not work well [78,79,80]. Solution-processed p-channel TFTs have become fundamental technology in flexible organic LED (OLED) and active-matrix OLED (AMOLED) displays. They exhibit flexibility, as evidenced by their capability for curve and roll formations, contributing to changes in smartphones, tablets, televisions, and wearable devices with display flexibility [81,82,83]. P-channel TFTs synthesized via solution processing can assist in the manufacture of electronic and e-skin devices, which reflect the functions of the skin layer of the human body. E-skin devices can capture signals through pressure, temperature, and humidity, making them useful in areas such as robotics, prosthetics, and human–machine interfaces [84,85]. Flexible circuits are important in flexible electronics and their applications owing to their ability to fold, twist, etc., while retaining their electrical capabilities. Flexible substrates are generally composed of polyimides and other materials that can provide thin/lightweight construction along with more design freedom. They are used in smart clothing and accessories, healthcare, portable electronics, automotive and aviation industries, and other products designed to be long-lasting [86,87].

3.5. Challenges

The challenges associated with the mechanical stability of solution-processed TFTs on flexible substrates include bending weakness, smoothing, and delamination. Several strategies have been proposed to improve the mechanical robustness and stability of flexible devices, including material selection, device design, and encapsulation techniques. The environmental stability of solution-processed TFTs is highly sensitive to moisture, oxygen, and temperature. To improve the performance and environmental stability of flexible devices, barrier coatings and encapsulation layers are necessary. Exploring the scalability of solution-processing techniques is also necessary for the large-scale production of flexible devices. The challenges of scaling-up solution-processed TFT fabrication, such as uniformity control, throughput, and cost, highlight the potential solutions for overcoming these challenges.

4. Conclusions and Outlook

In conclusion, a review of the recent progress in solution-processed p-channel TFTs is essential for studying the rapidly evolving fields of materials science, electronics, and flexible device engineering. The processing of solutions for p-type TFTs demonstrates excellent potential for CMOS applications together with flexible electronic systems and sensor-based and display functionalities. Research improvements in organic p-type materials have increased their mobility and stability while increasing their versatility levels. This review discussed the progress, issues, and novel generation of bendable electronic devices.

Author Contributions

Investigation and data curation, N.M., J.L. and S.C.; writing—original draft preparation, N.M.; writing—review and editing, S.C. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the Sunchon National University Research Fund in 2023 (Grant number: 2023-0317).

Data Availability Statement

No new data were created.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 2. Deposition techniques used in (a) vacuum and (b) solution processes. Reproduced with permission from [47]. Copyright 2011, Royal Society of Chemistry.
Figure 2. Deposition techniques used in (a) vacuum and (b) solution processes. Reproduced with permission from [47]. Copyright 2011, Royal Society of Chemistry.
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Figure 3. (a) CTS precursor solution schematic and TFT transfer curves (reproduced with permission [48], copyright 2021 Royal Society of Chemistry). (b) Schematic of CTSGO spin coating, UV/O3 curing, and annealing at 250 °C (2h, N2). Film formation mechanism: UV/O3 photocuring at 100 °C enhances the M-O-M network. (Reproduced with permission [49], copyright 2021 American Chemical Society). (c) Element mapping (Cu, Ni, Sn, O) and root-mean-square roughness variations with temperature of CuNiSnO (inset: AFM image at 100 °C). Also shown are the transfer and output characteristics (VDS = −5 V) of p-type a-CNTO TFTs at 100, 200, and 300 °C. The inset illustrates the TFT schematic. (Reproduced with permission [50], copyright 2020 IEEE).
Figure 3. (a) CTS precursor solution schematic and TFT transfer curves (reproduced with permission [48], copyright 2021 Royal Society of Chemistry). (b) Schematic of CTSGO spin coating, UV/O3 curing, and annealing at 250 °C (2h, N2). Film formation mechanism: UV/O3 photocuring at 100 °C enhances the M-O-M network. (Reproduced with permission [49], copyright 2021 American Chemical Society). (c) Element mapping (Cu, Ni, Sn, O) and root-mean-square roughness variations with temperature of CuNiSnO (inset: AFM image at 100 °C). Also shown are the transfer and output characteristics (VDS = −5 V) of p-type a-CNTO TFTs at 100, 200, and 300 °C. The inset illustrates the TFT schematic. (Reproduced with permission [50], copyright 2020 IEEE).
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Figure 4. (a) Chemical structures of CuSCN and C60F48, HOMO and LUMO of C60F48 from DFT calculations (Quantum Espresso), and energy-level diagram with Au electrodes. The transfer and output characteristics of CuSCN transistors with varying C60F48 concentrations and the square root of ID from the transfer curves during saturation. (Reproduced with permission [51], copyright 2018 WILEY-VCH). (b) All-carbon water-only printed TFTs: device structure and printing process, array and single-device images, subthreshold characteristics with “double minima” at low VDS, and output characteristics of organic device. (Reproduced with permission [52], copyright 2023 American Chemical Society). (c) Schematic cross-sections of coplanar BG-BC and staggered TG-BC CuSCN TFTs on polyimide substrates. Transfer and output characteristics of flexible low-voltage CuSCN p-type TFTs. (Reproduced with permission [53], copyright 2017 AIP Publishing.)
Figure 4. (a) Chemical structures of CuSCN and C60F48, HOMO and LUMO of C60F48 from DFT calculations (Quantum Espresso), and energy-level diagram with Au electrodes. The transfer and output characteristics of CuSCN transistors with varying C60F48 concentrations and the square root of ID from the transfer curves during saturation. (Reproduced with permission [51], copyright 2018 WILEY-VCH). (b) All-carbon water-only printed TFTs: device structure and printing process, array and single-device images, subthreshold characteristics with “double minima” at low VDS, and output characteristics of organic device. (Reproduced with permission [52], copyright 2023 American Chemical Society). (c) Schematic cross-sections of coplanar BG-BC and staggered TG-BC CuSCN TFTs on polyimide substrates. Transfer and output characteristics of flexible low-voltage CuSCN p-type TFTs. (Reproduced with permission [53], copyright 2017 AIP Publishing.)
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Figure 5. (a) Transfer characteristics of SCS-derived Cu:NiO TFTs with various rates of Cu doping, mobility, and Vth bar graphs. Circuit diagram of a green LED driven by a Cu5% NiO/ZrO2 TFT with LED intensity modulated by VGS. (Reproduced with permission [56], Copyright 2017 Wiley). (b) Schematic of Li:NiOx TFTs via the SUV route, transfer characteristics, and transmittance of Li5%:NiOx/ZrO2/ITO on PET. Transfer curves of the flexible TFT. (Reproduced with permission [57], Copyright 2018 Royal Society of Chemistry). (c) Transfer curves of CuI TFTs on flexible ITO/PET and transmittance data. (Reproduced with permission [58], Copyright 2023 Elsevier). (d) Schematic diagram and bending test results of SnO TFTs fabricated on flexible polyimide substrate [59].
Figure 5. (a) Transfer characteristics of SCS-derived Cu:NiO TFTs with various rates of Cu doping, mobility, and Vth bar graphs. Circuit diagram of a green LED driven by a Cu5% NiO/ZrO2 TFT with LED intensity modulated by VGS. (Reproduced with permission [56], Copyright 2017 Wiley). (b) Schematic of Li:NiOx TFTs via the SUV route, transfer characteristics, and transmittance of Li5%:NiOx/ZrO2/ITO on PET. Transfer curves of the flexible TFT. (Reproduced with permission [57], Copyright 2018 Royal Society of Chemistry). (c) Transfer curves of CuI TFTs on flexible ITO/PET and transmittance data. (Reproduced with permission [58], Copyright 2023 Elsevier). (d) Schematic diagram and bending test results of SnO TFTs fabricated on flexible polyimide substrate [59].
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Figure 6. Flexible electronics are widely used in various applications owing to their versatility and adaptability to curved or irregular surfaces. A few applications are mentioned next. Sensors. Reproduced with permission from [75]. Copyright 2019, MDPI. Reproduced with permission from [76]. Copyright 2019, Elsevier Ltd. Reproduced with permission from [77]. Copyright 2018, American Chemical Society. RFID. Reproduced with permission from [78]. Copyright 2014, Elsevier B.V. Reproduced with permission from [79]. Copyright 2018, MDPI. Reproduced with permission from [80]. Copyright 2019, WILEY-VCH. Display. Reproduced with permission from [81]. Copyright 2011, WILEY-VCH. Reproduced with permission from [82]. Copyright 2013, Nature Publishing Group. Reproduced with permission from [83]. Copyright 2018, WILEY-VCH. E-skin. Reproduced with permission from [84]. Copyright 2010, Nature Publishing Group. Reproduced with permission from [85]. Copyright 2014, Nature Publishing Group. Circuit. Reproduced with permission from [86]. Copyright 2012, American Chemical Society. Reproduced with permission from [87]. Copyright 2014, Society for Information Display.
Figure 6. Flexible electronics are widely used in various applications owing to their versatility and adaptability to curved or irregular surfaces. A few applications are mentioned next. Sensors. Reproduced with permission from [75]. Copyright 2019, MDPI. Reproduced with permission from [76]. Copyright 2019, Elsevier Ltd. Reproduced with permission from [77]. Copyright 2018, American Chemical Society. RFID. Reproduced with permission from [78]. Copyright 2014, Elsevier B.V. Reproduced with permission from [79]. Copyright 2018, MDPI. Reproduced with permission from [80]. Copyright 2019, WILEY-VCH. Display. Reproduced with permission from [81]. Copyright 2011, WILEY-VCH. Reproduced with permission from [82]. Copyright 2013, Nature Publishing Group. Reproduced with permission from [83]. Copyright 2018, WILEY-VCH. E-skin. Reproduced with permission from [84]. Copyright 2010, Nature Publishing Group. Reproduced with permission from [85]. Copyright 2014, Nature Publishing Group. Circuit. Reproduced with permission from [86]. Copyright 2012, American Chemical Society. Reproduced with permission from [87]. Copyright 2014, Society for Information Display.
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Table 1. Representative performance summary of state-of-the-art p-type TFTs.
Table 1. Representative performance summary of state-of-the-art p-type TFTs.
MethodChannelAnnealing Temp. (°C)μFE
(cm2 V−1 s−1)		Ion/IoffYearRef
Spin coatingSnO4500.13852012[34]
Spin coatingCu2O7000.16~1022013[37]
Spray coatingCu2O27510−4–10−31 × 10−22013[36]
Spin coatingNiO5000.14N.A.2014[60]
Spin coatingCuO5000.01~1032016[42]
Spin coatingSn-NiO2800.97~1042016[61]
Ink-jet printingCuI604.410−1–10−22016[40]
SputterGST2006.7~662018[62]
Spin coatingNiO3500.0122017[43]
Spin coatingCuO3001.20N.A.2017[63]
Ink-jet printingNiO2800.785.3 × 1042018[45]
Spin coatingCuIRT0.44~1022018[64]
Spin coatingCuOX2500.10~1042020[65]
SputterCuGaOX8000.74~1042020[66]
Spin coatingI:CuO5006.61 × 10−3~1042021[67]
Spin coatingCTS2502.43~1042021[48]
Chemical vapor depositionCuO400–6000.15~1012022[68]
SputterTe25030.95.8 × 1052022[69]
Spin coatingY:CuO2005.3~1042023[70]
Spin coatingWSe220027~1072023[71]
SputterCu2O8001.11 ± 0.05~1042023[72]
EvaporationTe-TeOx22515106–1072024[73]
Spin coatingCuGaOX2501.24~1042024[74]
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Mude, N.; Lee, J.; Cho, S. Recent Advancements in P-Type Inorganic Semiconductor Thin-Film Transistors: A Review. Crystals 2025, 15, 341. https://doi.org/10.3390/cryst15040341

AMA Style

Mude N, Lee J, Cho S. Recent Advancements in P-Type Inorganic Semiconductor Thin-Film Transistors: A Review. Crystals. 2025; 15(4):341. https://doi.org/10.3390/cryst15040341

Chicago/Turabian Style

Mude, Narendranaik, Jongsu Lee, and Sungwoon Cho. 2025. "Recent Advancements in P-Type Inorganic Semiconductor Thin-Film Transistors: A Review" Crystals 15, no. 4: 341. https://doi.org/10.3390/cryst15040341

APA Style

Mude, N., Lee, J., & Cho, S. (2025). Recent Advancements in P-Type Inorganic Semiconductor Thin-Film Transistors: A Review. Crystals, 15(4), 341. https://doi.org/10.3390/cryst15040341

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