Search Results (199)

CuSCN is a low-cost inorganic HTL with potentially better ambient stability than Spiro-OMeTAD according to literature. This study explores copper(I) thiocyanate (CuSCN) as a hole transport layer (HTL) to replace the conventional organic material Spiro-OMeTAD in antimony selenosulfide (Sb₂(S,Se)₃) solar cells. Numerical simulations performed with the Afors-het software reveal that the device structure FTO/CdS/Sb₂(S,Se)₃/CuSCN/Au incorporating CuSCN achieves improved interfacial energy band alignment. Specifically, the valence band offset (VBO) is reduced to −0.2 eV, which substantially enhances hole extraction efficiency and suppresses interface recombination. Through systematic optimization of key structural parameters, including the absorber layer thickness (350 nm), the CuSCN layer thickness (9 nm), and its p-type doping concentration (10¹⁹ cm⁻³), the device attains a maximum power conversion efficiency (PCE) of 12.03%. This work provides a theoretical foundation and a viable device design strategy for developing low-cost, highly stable, and efficient Sb₂(S,Se)₃ solar cells. Full article

The performance of inverted CH₃NH₃GeI₃ (MAGeI₃) perovskite solar cells incorporating both a hole transport layer (HTL) and an electron transport layer (ETL) was investigated using the Solar Cell Capacitance Simulator (SCAPS). Three candidate HTLs, including PEDOT:PSS, MoS₂, and WS₂, along with five ETLs including PCBM, TiO₂, IGZO, ZnO, and SnO₂, have been systematically evaluated. The analysis shows that WS₂ and SnO₂ provided the most favorable hole and electron transport, respectively. To improve device efficiency, the absorber layer thickness, defect density in MAGeI₃, doping levels of WS₂ and SnO₂, as well as the interface defect densities and the work function of indium tin oxide (ITO), have been systematically studied. The optimal absorber layer thickness is determined to be approximately 900 nm. The optimal doping density of both WS₂ and SnO₂ is 1 × 10¹⁹ cm⁻³. The MAGeI₃ layer should maintain a defect density as low as 1 × 10¹⁵ cm⁻³, and the defect densities at MAGeI₃ interfaces should remain at 1 × 10¹⁵ cm⁻². Additionally, an ITO work function of at least 5.2 eV is necessary to prevent the formation of a Schottky barrier at the ITO/WS₂ interface. The simulated power conversion efficiency (PCE) can reach 22.9% under these optimized conditions. Our simulation results offer a viable route to develop high-efficiency MAGeI₃ perovskite solar cells. Full article

Substoichiometric molybdenum oxide is widely utilized as a hole transport layer (HTL) in polymer solar cells and perovskite solar cells. In this study, the possibility of developing MoOx layers applicable as HTLs with different characteristics by magnetron sputtering from a MoO₃ target and annealing in dry nitrogen or air is explored. The optical transmission and reflection, optical band gap, FTIR and Raman spectra, crystallinity, conductivity, and work function of the films are studied depending on deposition and annealing conditions. The results demonstrate that it is possible to tune the properties of the obtained films with a view toward their application in solar cells. Full article

In scientific research, the optimization of organic light-emitting diodes (OLEDs) is generally achieved through a lengthy and expensive experimental process as new ideas and configurations are tested on real devices. Electro-optical simulation allows for the rapid evaluation of key performance parameters of device structures, thus reducing manufacturing time and costs. This paper presents an original contribution to the electro-optical modeling and optimization of multilayer OLED devices using the Non-dominated Sorting Genetic Algorithm II (NSGA-II). This optimization explicitly incorporates defect states within the ITO/NPB/Alq₃:C545T/Alq₃/LiF-Al structure. The simulated model is calibrated using experimental data by fitting the trap state distribution. The Pareto front resulting from the multi-objective optimization identifies a set of non-dominated configurations, including an optimal intermediate structure defined by an electron transport layer (ETL) thickness of approximately 42 nm and a hole transport layer (HTL) thickness of approximately 53 nm. This configuration leads to a limited reduction of 1.75–2% in current efficiency (${\eta }_c$) while offering a remarkable improvement of 23–30% in power efficiency (${\eta }_p$) compared to the extreme configurations of the optimal Pareto set. Thus, this solution represents an optimal Pareto trade-off between high current efficiency and improved power efficiency. This paper shows that combining defect modeling and thickness optimization provides a reliable framework for the electro-optical optimization of OLED devices. Future work will extend this approach to spectral and colorimetric analysis. Full article

The hole injection layer (HIL) plays a critical role in achieving high efficiency and operational stability in organic light-emitting diodes (OLEDs). As a commonly used HIL, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is limited by its intrinsically low electrical conductivity and mismatched work function alignment with the hole transport layer (HTL), leading to inefficient hole injection and carrier imbalance. In this work, a mild citric acid (CA) treatment is used to simultaneously enhance the conductivity of PEDOT:PSS through the partial removal of insulating PSS and tune its work function for improved energy level alignment at the anode interface. This simultaneous optimization effectively enhances the hole transport capability, successfully matching the electron transport capability to realize highly improved charge carrier balance within the device. Consequently, Ir(ppy)₃-based phosphorescent OLEDs featuring the optimally treated PEDOT:PSS HIL deliver a maximum external quantum efficiency of 20.37%, representing a 21% improvement over devices using pristine PEDOT:PSS, along with a twofold extension in operational lifetime. This strategy demonstrates a simple and controllable approach to interfacial engineering, providing practical guidance for the development of high-performance and stable OLEDs. Full article

The discovery of quantum dots (QDs) earned a Nobel Prize and has led to widespread applications in research and technology. In this review, we focus on the use of QDs in solid-state solar cells (QDSCs). We begin with an overview of the basic principles of SCs. Then, we discuss how device architecture has developed over recent decades, setting the stage for the final section on fourth-generation solar cells (Perspective section). We also highlight progress in material development, starting with lead- and cadmium-based QDs and progressing to more recent carbon- and perovskite-based QDs. Additionally, we review materials used for electron-transport layers (ETLs) and hole-transport layers (HTLs). The articles also present recent advances in QDSCs across various QD types. In the final section, we recommend that future research focus on three main areas: QD active-layer materials, material interfaces, and device architecture. These efforts could lead to sustainable QDSCs that potentially surpass the Shockley–Queisser (SQ) limit. Full article

Energy losses induced by inefficient charge transfer and large energy-level offsets at the interface limit the efficiency of CdTe nanocrystal (NC) solar cells. In this work, organic poly(triaryl amine) (PTAA) and inorganic CuI which form double hole transport layers (HTLs) are first proposed to improve the charge transfer capability of hole transport layers (HTLs) and reduce the band offset at the interface of CdTe NCs. The introduced CuI improves carrier mobility, while PTAA reduces interface recombination and reinforces the inner built-in field, resulting in low energy loss from the CdTe NC active layer to the contact electrode. Photovoltaic devices using these modified back contacts show increases in both open-circuit voltage and short-circuit current, compared to a controlled device without HTL. The CdTe NCs utilizing CuI-PTAA double HTLs demonstrate a high power conversion efficiency (PCE) of 7.36%. High stability is also demonstrated, with PCE loss being less than 5% after tracking for 30 days. This work provides an effective way to minimize energy loss at the interface of the back contact in inverted CdTe NCs solar cells, by incorporating proper hole transfer layer design. Full article

Owing to their superior color purity and solution-processability, quantum dot light-emitting diodes (QLEDs) have garnered significant attention as promising candidates for next-generation displays. However, overcoming efficiency degradation and limited operational lifetime, which stem from charge transport imbalance, remains a critical challenge. Herein, we systematically discuss the role of the hole transport layer (HTL) in mitigating this imbalance. We classify HTL engineering strategies into four key categories: energy-level alignment, hole mobility and carrier concentration control, improvement in solvent stability, and multilayer architectures. Furthermore, we discuss hybrid HTL architectures that integrate multiple strategies to achieve synergistic improvement. Ultimately, this review highlights the pivotal role of HTL engineering in realizing high-performance QLEDs and provides insightful perspectives on future research directions. Full article

Nanomaterial-based hole transport layers (HTLs) play a vital role in regulating interfacial charge extraction and recombination in perovskite solar cells (PSCs). To improve PSC efficiency, hydrothermally synthesized CeO₂@MoS₂ nanocomposites (CM NCs) were incorporated as an interfacial buffer layer into a NiO_X/MeO-2PACz HTL. The introduction of CM NCs induces strong interfacial interactions, where Mo sites in MoS₂ interact with NiO_X, modulating the Ni²⁺/Ni³⁺ ratio and reducing the interfacial trap density. Moreover, CeO₂ promotes the formation of oxygen vacancies, collectively improving the conductivity and hole transport capability of the NiO_X HTL. The MoS₂-grafted CeO₂ interlayer effectively tailors the interfacial energetics and creates an effective channel for hole transfer, thereby reducing open-circuit voltage (V_OC) loss and enhancing device performance. This interface modification efficiently enhances hole extraction, and non-radiative recombination is effectively suppressed at the NiO_X/MeO-2PACz/perovskite interface. Thereby, incorporating 2 vol% CM NCs into PSCs achieved a power conversion efficiency (PCE) of 17.93%, compared to 17.50% for a 1 vol% CM NCs-based device and 17.01% for the unmodified control device. The enhanced performance at the optimized CM NCs concentration is attributed to effective defect passivation, reduced V_OC loss, and improved interfacial band alignment, which together facilitate hole extraction and suppress non-radiative recombination. However, excessive CM NCs incorporation (4 vol%) leads to increased interfacial resistance, partial hole blocking effects associated with the n-type nature of CeO₂, and aggravated recombination, resulting in degraded device performance. These results demonstrate that precise control over CM NCs interlayer thickness and concentration is critical for maximizing device performance, providing a robust strategy for designing high-efficiency and stable NiO_X-based PSCs and advancing nanocomposite-enabled interfacial engineering for photovoltaic applications. Full article

Self-powered perovskite photodiodes provide an attractive platform for low-power and high-sensitivity photodetection; however, their performance capabilities are often constrained by inefficient interfacial charge extraction and noise suppression. Here, we report a polymer-mediated interfacial engineering strategy for methylammonium lead iodide (MAPbI₃) photodiodes by integrating thermally optimized nickel oxide (NiO_x) hole-transport layers (HTLs) with a nonionic polymeric surfactant, poly(oxyethylene)(10) tridecyl ether (PTE). NiO_x films annealed at 300 °C establish a favorable energetic baseline for hole extraction, while the ppm-level incorporation of PTE into the MAPbI₃ precursor enables the molecular-scale modulation of the NiO_x/MAPbI₃ interface without forming an additional interlayer. The external quantum efficiency at 640 nm increases from 78.7% for pristine MAPbI₃ to 84.1% and 84.6% for devices incorporating 30 and 60 ppm PTE, corresponding to enhanced responsivities of 406, 434, and 437 mA/W. These improvements translate into reduced noise-equivalent power and an increase in the noise-limited detectivity from 2.50 × 10¹² to 2.76 × 10¹² Jones under zero-bias operation. Importantly, enhanced sensitivity is achieved without compromising the dynamic performance, as all devices retain fast temporal responses and kilohertz-level bandwidths. These results establish polymeric-surfactant-assisted interfacial engineering as a scalable and effective platform for low-noise, high-sensitivity self-powered perovskite photodiodes for renewable-energy-integrated systems. Full article

The increasing impact of global warming is predominantly driven by the extensive use of fossil fuels, which release significant amounts of greenhouse gases into the atmosphere. This has led to a critical need for alternative, sustainable energy sources that can mitigate environmental impacts. Photovoltaic technology has emerged as a promising solution by harnessing renewable energy from the sun, providing a clean and inexhaustible power source. Perovskite solar cells (PSCs) are a class of hybrid organic–inorganic solar cells that have recently attracted significant scientific attention due to their low cost, relatively high efficiency, low–temperature processing routes, and longer carrier lifetimes. These characteristics make them a viable alternative to traditional fossil fuels, reducing the carbon footprint and contributing to the fight against global warming. In this study, the SCAPS–1D numerical simulator was used in the computational analysis of a PSC device with the configuration FTO/ETL/BaZr(S_0.6Se_0.4)₃/HTL/Ir. Different hole transport layer (HTL) and electron transport layer (ETL) material were proposed and tested. The HTL materials included copper (I) oxide (Cu₂O), 2,2′,7,7′–Tetrakis(N,N–di–p–methoxyphenylamine)9,9′–spirobifluorene (spiro–OMETAD), and poly(3–hexylthiophene) (P₃HT), while the ETLs included cadmium suphide (CdS), zinc oxide (ZnO), and [6,6]–phenyl–C₆₁–butyric acid methyl ester (PCBM). Finally, BaZr(S_0.6Se_0.4)₃ was proposed as an absorber, and a fluorine–doped tin oxide glass substrate (FTO) was proposed as an anode. The metal back contact used was iridium. Photovoltaic parameters such as short circuit density (I_sc), open circuit voltage (V_oc), fill factor (FF), and power conversion efficiency (PCE) were used to evaluate the performance of the device. The initial simulated primary device with the configuration FTO/CdS/BaZr(S_0.6Se_0.4)₃/spiro–OMETAD/Ir gave a PCE of 5.75%. Upon testing different HTL materials, the best HTL was found to be Cu₂O, and the PCE improved to 9.91%. Thereafter, different ETLs were also inserted and tested, and the best ETL was established to be ZnO, with a PCE of 10.10%. Ultimately an optimized device with a configuration of FTO/ZnO/BaZr(S_0.6Se_0.4)₃/Cu₂O/Ir was achieved. The other photovoltaic parameters for the optimized device were as follows: FF = 31.93%, J_sc = 14.51 mA cm⁻², and V_oc = 2.18 V. The results of this study will promote the use of environmentally benign BaZr(S_0.6Se_0.4)₃–based absorber materials in PSCs for improved performance and commercialization. Full article

This study investigates the feasibility of adding gold nanoparticles (Au-NPs) to vanadium oxide (V₂O_x) serving the hole transport layer (HTL) material oin polymer solar cells to enhance cell performance. The first part of this study used Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as a baseline and optimized the parameters of this HTL material. Then, the V₂O_x was substituted as the HTL material, and its parameters were optimized again. The second part involved incorporating an aqueous solution of gold nanoparticles (Au-NPs) with an average particle size of approximately 80 nm into V₂O_x. Due to the excitation of localized surface plasmon resonance (LSPR) by Au-NPs, the addition of Au-NPs to the V₂O_x layer can enhance the absorption efficiency of the P3HT:PCBM blended film. Therefore, compared with V₂O_x alone, the solar cells with Au-NPs incorporated into the V₂O₅ hole transport layer demonstrate improved power conversion efficiency (PCE). Full article

Molybdenum oxide (MoO_X) has been widely utilized as a hole transport layer (HTL) in crystalline silicon (c-Si) solar cells, owing to characteristics such as a wide bandgap and high work function. However, the relatively low conductivity of MoO_X films and their poor contact performance at the MoO_X-based hole-selective contact severely degrade device performance, particularly because they limit the fill factor (FF). Oxygen vacancies are of paramount importance in governing the conductivity of MoO_X films. In this work, MoO_X films were modified through ultraviolet irradiation (UV-MoO_X), resulting in MoO_X films with tunable oxygen vacancies. Compared to untreated MoO_X films, UV-MoO_X films contain a higher density of oxygen vacancies, leading to an enhancement in conductivity (2.124 × 10⁻³ S/m). In addition, the UV-MoO_X rear contact exhibits excellent contact performance, with a contact resistance of 20.61 mΩ·cm², which is significantly lower than that of the untreated device. Consequently, the application of UV-MoO_X enables outstanding hole selectivity. The power conversion efficiency (PCE) of the solar cell with an n-Si/i-a-Si:H/UV-MoO_X/Ag rear contact reaches 24.15%, with an excellent FF of 84.82%. Full article

In response to the rising global energy dilemma and associated environmental concerns, research into creating less hazardous solar technology has exploded. Due to their cost-effective fabrication process and exceptional optoelectronic properties, perovskite-based solar cells have emerged as promising candidates. However, their commercialization faces obstacles, including lead contamination, interface recombination, and instability. This study examines CaV_0.5Fe_0.5O₃ (CVFO) as an alternative to lead-based perovskites, highlighting its improved stability and high efficiency through a series of simulation and modeling results. A record power conversion efficiency (PCE) of 23.28% was achieved (V_oc = 1.38 V, J_sc = 19.8 mA/cm², FF = 85.2%) using a 550 nm thick CaV_0.5Fe_0.5O₃ as an absorber. This was accomplished by optimizing the electron transport layer (ETL: TiO₂, 40 nm, 10²⁰ cm⁻³ doping) and the hole transport layer (HTL: Cu₂O, 50 nm, 10²⁰ cm⁻³ doping). Subsequently, it was established that defects at the ETL/perovskite interface significantly diminish performance relative to defects on the HTL side, and thermal stability assessments verified proper operation up to 350 K. To maintain efficiency, it is necessary to reduce series resistance (R_s < 1 Ω·cm²) and increase shunt resistance (R_sh > 10⁴ Ω·cm²). The findings indicate that CaV_0.5Fe_0.5O₃ serves as a feasible alternative to perovskites and has the potential to enhance the performance of scalable solar cells. Full article

In this study, p-type NiO_x and Cu-doped NiO_x nanoparticles (NPs) were synthesized by a simple chemical precipitation method and used as hole transport layers (HTLs) for inverted perovskite solar cells (PSCs). The microstructural property, surface morphology, elemental composition, optical property, charge recombination, and surface topography of the NiO_x and Cu-NiO_x HTLs were comprehensively characterized. The results showed that the NiO_x and Cu-NiO_x NPs were uniformly coated on the substrates without pinholes or voids. Cu incorporation into NiO_x did not change its crystalline nature and considerably improved its electrical conductivity. The Cu-NiO_x HTLs exhibited superior photoluminescence quenching and the least lifetime decay, which indicated that Cu-NiO_x exhibited higher charge transport than NiO_x HTLs. The fabricated PSC performances were further analyzed using current density–voltage characteristics, external quantum efficiency, and electrochemical impedance spectroscopy. The PSCs with PEDOT:PSS, NiO_x, and 2% Cu-NiO_x HTLs exhibited power conversion efficiencies of 11.93%, 13.72%, and 15.54%, respectively. The 2% Cu-NiO_x HTL-based device showed the best performance compared with the PEDOT:PSS- and NiO_x-based devices. Academic Editors: Chunyang Zhang, Dou Zhang Full article