Search Results (24)

Organic phototransistors exhibit considerably higher photoresponsivity than diode-like photodetectors owing to gate-field-effect amplification. However, the conventional definition of photoresponsivity (R) fails to accurately capture the photoresponsivity trends of transistor-based photodetectors. This study systematically investigates the impact of device geometry—specifically the width-to-length (W/L) ratio and photosensitive area—on the responsivity and photocurrent of organic phototransistors. The experimental results reveal that increasing the W/L ratio or decreasing the device area substantially enhances responsivity. A detailed analysis based on the definition of responsivity is presented herein. Finally, we introduce a channel-width-normalized responsivity to compensate for geometric effects, enabling a more accurate evaluation of device performance across different device structures. Overall, our results indicate the potential for optimizing organic phototransistors by tuning their geometric parameters. Full article

We investigate the inorganic/organic hybrid vertical phototransistor (VPT) by integrating an atomic layer deposition-processed ZnO (ALD-ZnO) transistor with a prototype poly(3-hexylthiophene):[6,6]-phenyl-C₆₁-butyric acid methyl ester (P3HT:PC₆₁BM) blend organic photodiode (OPD) based on an encapsulated source electrode geometry, and discuss the device mechanism. Our preliminary studies on reference P3HT:PC₆₁BM OPDs show non-ohmic electron injection between the ALD-ZnO and P3HT:PC₆₁BM layers. However, the ALD-ZnO layer enables the accumulation of photogenerated holes under negative bias, which facilitates electron injection upon illumination and thereby enhances the external quantum efficiency (EQE). This mechanism underpins the photoresponse in the VPT. Furthermore, we demonstrate that the gate field in the VPT effectively modulates electron injection from the ALD-ZnO layer to the top OPD, resulting in the VPT operating as a non-ohmic OPD in the OFF state and as an ohmic OPD in the ON state. Benefiting from the unique transistor geometry and gate modulation capability, this hybrid VPT can achieve an EQE of 45,917%, a responsivity of 197 A/W, and a specific detectivity of 3.4 × 10¹² Jones under 532 nm illumination and low drain-source voltage (V_ds = 3 V) conditions. This transistor geometry also facilitates integration with various OPDs and the miniaturization of the ZnO channel area, offering an ideal basis for the development of highly efficient VPTs and high-resolution image sensors. Full article

This review provides a comprehensive overview of recent advancements in the synthesis, properties, and applications of organic materials in the optoelectronics sector. The study emphasizes the critical role of organic materials in the development of state-of-the-art optoelectronic devices such as organic solar cells, organic thin-film transistors, and OLEDs. The review further examines the structure, operational principles, and performance metrics of organic optoelectronic devices. Organic materials have emerged as promising candidates due to their low-cost production and potential for large-area or flexible substrate applications. Additionally, this review highlights the physical mechanisms governing the optoelectronic properties of high-performance organic materials, particularly photoinduced processes relevant to charge carrier photogeneration. It discusses the unique benefits of organic materials over traditional inorganic materials, including their light weight, simple processing, and flexibility. The report delves into the challenges related to stability, scalability, and performance, while highlighting the wide range of electronic properties exhibited by organic materials, which are critical for their performances in optoelectronic devices. Furthermore, it addresses the need for further research and development in this field to achieve consistent performance across different types of devices. Full article

Organic phototransistors, renowned for their exceptional biocompatibility, hold promise in phototherapy for tracking the efficacy of photosensitive drugs within treatment areas. Nevertheless, it has been found that organic semiconductors are less effective in detecting ultraviolet (UV) light because of their narrow bandgap. Here, we show that UV photodetection in phototransistors using donor-acceptor (D-A) polymer semiconductors can be significantly enhanced by incorporating PCBM nanocrystals. This integration results in a band mismatch between the nanocrystals and the D-A polymer at the interface. These nanocrystals also demonstrate a notable capability of modulating threshold voltage under UV light. The devices incorporating nanocrystals exhibit a photoresponsivity of 0.16 A/W, surpassing the photoresponsivity of the devices without nanocrystals by 50%. The specific detection rate of devices with nanocrystals is around 2.00 × 10¹⁰ Jones, which is twice as high as that of devices without nanocrystals. The presented findings offer a potential avenue to improve the efficiency of polymer phototransistors for UV detection. Full article

Phototransistors are three-terminal photodetectors that usually have a higher photocurrent gain than photodiodes due to the amplification of the gate electrode. In this work, a broad spectral phototransistor based on copper phthalocyanine (CuPc) and a Cs₃Bi₂I₉ (CBI) heterojunction is fabricated by the full vacuum evaporation method. Due to the complementary UV–visible absorption of CuPc and CBI, the device exhibits superior performance under three different types of visible light illumination. The experimental results show that the structure of the organic/perovskite heterojunction active layer has the characteristics of good compatibility and a simple process. Meanwhile, by utilizing the superior light-absorption characteristics of perovskite materials and the strong exciton dissociation efficiency of a hetero-type heterojunction interface, the CuPc/CBI-PT exhibits a higher photoresponsivity, photosensitivity, specific detection rate, and lower operating voltage than the CuPc reference device. The stability test shows that the CuPc/CBI-PT can still obtain a 0.73 A/W photoresponsivity under 660 nm light illumination after being stored in the air for 360 h without any packaging. This indicates that the organic/perovskite heterojunction PT may be a good choice for the preparation of high-performance photodetectors. Full article

This review comprehensively addresses the developments and applications of polymer materials in optoelectronics. Especially, this review introduces how the materials absorb, emit, and transfer charges, including the exciton–vibrational coupling, nonradiative and radiative processes, Förster Resonance Energy Transfer (FRET), and energy dynamics. Furthermore, it outlines charge trapping and recombination in the materials and draws the corresponding practical implications. The following section focuses on the practical application of organic materials in optoelectronics devices and highlights the detailed structure, operational principle, and performance metrics of organic photovoltaic cells (OPVs), organic light-emitting diodes (OLEDs), organic photodetectors, and organic transistors in detail. Finally, this study underscores the transformative impact of organic materials on the evolution of optoelectronics, providing a comprehensive understanding of their properties, mechanisms, and diverse applications that contribute to advancing innovative technologies in the field. Full article

Merging the functionality of an organic field-effect transistor (OFET) with either a light emission or a photoelectric effect can increase the efficiency of displays or photosensing devices. In this work, we show that an organic semiconductor enables a multifunctional OFET combining electroluminescence (EL) and a photoelectric effect. Specifically, our computational and experimental investigations of a six-ring thiophene-phenylene co-oligomer (TPCO) revealed that this material is promising for OFETs, light-emitting, and photoelectric devices because of the large oscillator strength of the lowest-energy singlet transition, efficient luminescence, pronounced delocalization of the excited state, and balanced charge transport. The fabricated OFETs showed a photoelectric response for wavelengths shorter than 530 nm and simultaneously EL in the transistor channel, with a maximum at ~570 nm. The devices demonstrated an EL external quantum efficiency (EQE) of ~1.4% and a photoelectric responsivity of ~0.7 A W^–1, which are among the best values reported for state-of-the-art organic light-emitting transistors and phototransistors, respectively. We anticipate that our results will stimulate the design of efficient materials for multifunctional organic optoelectronic devices and expand the potential applications of organic (opto)electronics. Full article

Perovskite-based metal oxide phototransistors have emerged as promising photodetection devices owing to the superior optoelectronic properties of perovskite materials and the high carrier mobility of metal oxides. However, high dark current has been one major problem for this type of device. Here, we studied the dark current behaviors of phototransistors fabricated based on the Indium Gallium Zinc Oxide (IGZO) channel and different perovskite materials. We found that depositing organic–inorganic hybrid perovskites materials (MAPbI₃/FAPbI₃/FA_0.2MA_0.8PbI₃) on top of IGZO transistor can increase dark current from ~10⁻⁶ mA to 1~10 mA. By contrast, we observed depositing an inorganic perovskite material, CsPbI₃, incorporated with PCBM additive can suppress the dark current down to ~10⁻⁶ mA. Our study of ion migration reveals that ion migration is pronounced in organic–inorganic perovskite films but is suppressed in CsPbI₃, particularly in CsPbI₃ mixed with PCBM additive. This study shows that ion migration suppression by the exclusion of organic halide and the incorporation of PCBM additive can benefit low dark current in perovskite phototransistors. Full article

Near-infrared (NIR) light has many applications in agriculture, transportation, medicine, the military, and other fields. Lead phthalocyanine (PbPc) exhibits excellent near-infrared (NIR) light absorption characteristics and is widely used in NIR-sensitive organic photodetectors. In this work, PbPc-based NIR organic phototransistors (OPTs) with different active layer structures were designed and fabricated. The photo-absorption characteristics of organic films, photosensitive properties, and air stability of the devices were investigated. The results suggested that (i) the bilayer planar heterojunction (PHJ) devices exhibit far better photosensitive performance than the single layer ones due to higher mobility of the formers than the latters; (ii) the bilayer PHJ ones with p-type channel have equivalent photosensitive performance to those with n-type channel owing to equivalent mobility, higher NIR absorption and lower exciton dissociation efficiency of the formers than the latters; (iii) the bilayer PHJ ones with p-type channel possess superior air stability to those with n-type channel thanks to better air stability of pentacene channel layer than C₆₀ channel layer; (iv) the tri-layer PHJ ones perform better than the bilayer PHJ ones with p-type channel and exhibit a high photoresponsivity of 1415 mA/W and a maximum photo-to-dark current ratio of 1.2 × 10⁴, and such an outstanding performance benefits from the virtues of tri-layer PHJ structure including high light absorption, carrier mobility and exciton dissociation efficiency; and (v) the air stability of the tri-layer PHJ ones is better than that of the bilayer PHJ ones with p-type channel, which can be attributed to the passivation of the top-level C₆₀ layer. Full article

The fabrication of high-performance Organic Phototransistors (OPTs) by depositing Al-islands atop Poly(3-hexylthiophene) (P3HT) thin film coated using the unidirectional floating-film transfer method (UFTM) has been realized. Further, the effect of Al-island thickness on the OPTs’ performance has been intensively investigated using X-ray photoelectron spectroscopy, X-ray Diffraction, Atomic force microscopy and UV-Vis spectroscopy analysis. Under the optimized conditions, OPTs’ mobility and on–off ratio were found to be 2 × 10⁻² cm² V⁻¹ s⁻¹ and 3 × 10⁴, respectively. Further, the device exhibited high photosensitivity of 10⁵, responsivity of 339 A/W, detectivity of 3 × 10¹⁴ Jones, and external quantum efficiency of 7.8 × 10³% when illuminated with a 525 nm LED laser (0.3 mW/cm²). Full article

Over the past years, molybdenum disulfide (MoS₂) has been the most extensively studied two-dimensional (2D) semiconductormaterial. With unique electrical and optical properties, 2DMoS₂ is considered to be a promising candidate for future nanoscale electronic and optoelectronic devices. However, charge trapping leads to a persistent photoconductance (PPC), hindering its use for optoelectronic applications. To overcome these drawbacks and improve the optoelectronic performance, organic semiconductors (OSCs) are selected to passivate surface defects, tune the optical characteristics, and modify the doping polarity of 2D MoS₂. Here, we demonstrate a fast photoresponse in multilayer (ML) MoS₂ by addressing a heterojunction interface with vanadylphthalocyanine (VOPc) molecules. The MoS₂/VOPc van der Waals interaction that has been established encourages the PPC effect in MoS₂ by rapidly segregating photo-generated holes, which move away from the traps of MoS₂ toward the VOPc molecules. The MoS₂/VOPc phototransistor exhibits a fast photo response of less than 15 ms for decay and rise, which is enhanced by 3ordersof magnitude in comparison to that of a pristine MoS₂-based phototransistor (seconds to tens of seconds). This work offers a means to realize high-performance transition metal dichalcogenide (TMD)-based photodetection with a fast response speed. Full article

Organic phototransistors (OPTs) as optical chemical sensors have progressed excitingly in recent years, mainly due to the development of new materials, new device structures, and device interfacial engineering. Exploiting the maximum potential of low-cost and high-throughput fabrication of organic electronics and optoelectronics requires devices that can be manufactured in a fully printed way that also have a low operation voltage. In this work, we demonstrate a fully printed fabrication process that enables the realization of a high-yield (~90%) and low-voltage OPT array. By solution printing of a high-quality organic crystalline thin film on the pre-printed electrodes, we create a van der Waals contact between the metal and organic semiconductor, resulting in a small subthreshold swing of 445 mV dec⁻¹ with a signal amplification efficiency over 5.58 S A⁻¹. Our OPTs thus exhibit both a low operation voltage of −1 V and a high photosensitivity over 5.7 × 10⁵, making these devices suitable for a range of applications requiring low power consumption. We further demonstrate the capability of the low-voltage OPT array for imaging and show high imaging contrasts. These results indicate that our fabrication process may provide an entry into integrated and low-power organic optoelectronic circuits fabricated by scalable and cost-effective methods for real-world applications. Full article

Organic phototransistors exhibit great promise for use in a wide range of technological applications due to their flexibility, low cost, and low-temperature processability. However, their low transparency due to visible light absorption has hindered their adoption in next-generation transparent electronics. For this reason, the present study sought to develop a highly sensitive organic phototransistor with greater transparency and significantly higher light sensitivity in the visible and UVA regions without deterioration in its electrical properties. An organic blended thin-film transistor (TFT) fabricated from the blend of an organic semiconductor and an insulating polymer demonstrated improved electrical properties in the dark and a higher current under light irradiation even though its transmittance was higher. The device exhibited a transmittance of 87.28% and a photosensitivity of 7049.96 in the visible light region that were 4.37% and 980 times higher than those of the single-semiconductor-based device. The carrier mobility of the device blended with the insulating polymer was improved and greatly amplified under light irradiation. It is believed that the insulating polymer facilitated the crystallization of the organic semiconductor, thus promoting the flow of photogenerated excitons and improving the photocurrent. Overall, the proposed TFT offers excellent low-temperature processability and has the potential to be employed in a range of transparent electronic applications. Full article

The photosensitivity, responsivity, and signal-to-noise ratio of organic phototransistors depend on the timing characteristics of light pulses. However, in the literature, such figures of merit (FoM) are typically extracted in stationary conditions, very often from IV curves taken under constant light exposure. In this work, we studied the most relevant FoM of a DNTT-based organic phototransistor as a function of the timing parameters of light pulses, to assess the device suitability for real-time applications. The dynamic response to light pulse bursts at ~470 nm (close to the DNTT absorption peak) was characterized at different irradiances under various working conditions, such as pulse width and duty cycle. Several bias voltages were explored to allow for a trade-off to be made between operating points. Amplitude distortion in response to light pulse bursts was also addressed. Full article