Electron Transport Layer Research Articles

High efficiency carbon-based CsPbI2Br solar cells achieved by bidirectional passivation of cadmium p-aminobenzoate

The tin dioxide (SnO2) layer is commonly used as a traditional electron transport layer (ETL) in perovskite solar cells. However, it exists numerous defects in interior and on surface, diminishing the electron transport rate and causing energy level mismatches, thereby limiting the photoelectric conversion efficiency (PCE). In this study, cadmium p-aminobenzoate (PABACd) is synthesized using the displacement reaction and applied to modify the interface between the SnO2 ETL and CsPbI2Br film to achieve bidirectional passivation. Cd2+ effectively passivates defects in the ETL and penetrates perovskite crystals, contributing to defect passivation. Furthermore, PABA− stabilizes the [PbX6]4− octahedron, enhancing the stability of CsPbI2Br perovskite solar cells (PSCs). As a result of these interactions, the PABACd-optimized device achieved a maximum PCE of 14.34 % and an outstanding open-circuit voltage of 1.27 V. Simultaneously, the PCE of the optimized CsPbI2Br PSCs remains at 92 % of the initial efficiency after 30 days of aging in an air environment with 15–20 % humidity.

Unraveling the Positive Effects of Glycine Hydrochloride on the Performance of Pb–Sn‐Based Perovskite Solar Cells

Additives are commonly used to increase the performance of metal‐halide perovskite solar cells, but detailed information on the origin of the beneficial outcome is often lacking. Herein, the effect of glycine hydrochloride is investigated when used as an additive during solution processing of narrow‐bandgap mixed Pb–Sn perovskites. By combining the characterization of the photovoltaic performance and stability under illumination, with determining the quasi‐Fermi level splitting, time‐resolved microwave conductivity (TRMC), and morphological and elemental analysis a comprehensive insight is obtained. Glycine hydrochloride is able to retard the oxidation of Sn2+ in the precursor solution, and at low concentrations (1–2 mol%) it improves the grain size distribution and crystallization of the perovskite, causing a smoother and more compact layer, reducing non‐radiative recombination, and enhancing the lifetime of photogenerated charges. These improve the photovoltaic performance and have a positive effect on stability. By determining the quasi‐Fermi level splitting on perovskite layers without and with charge transport layers it is found that glycine hydrochloride primarily improves the bulk of the perovskite layer and does not contribute significantly to passivation of the interfaces of the perovskite with either the hole or electron transport layer (ETL).

Tin oxides@stannous pyrophosphate colloidal quantum dots as multifunctional electron transporting layer for efficient and stable perovskite solar cells

Perovskite solar cells (PSCs) are anticipated to spearhead the revolution in solar energy technology. Engineering the electron transporting layer (ETL)/perovskite heterointerface is known to be a key point for further high-performance PSCs because it determines the main charge transporting and energy losses. However, the most advanced SnO2 colloidal precursors tend to exhibit agglomeration and structural flaws, thereby deteriorating the morphology and electronic mass of the obtained ETL. Here, we polished the microstructure of the SnO2 surface by self-assembling SnO2@Sn2P2O7 quantum dots (SPOS), which is synthesized by the chemical reaction between hypophosphoric acid (H3PO2) and SnO2. The Sn2P2O7 was synthesized on the SnO2 surface, terminating the surface dangling bonds and resulting in steady SPOS quantum dots with smooth microstructure. The SPOS ETL with good optical and electrical properties as well as matched bandgap alignment with perovskite, yielding an improved power conversion efficiency of 23.35% for PSCs. Moreover, due to the suppression of defect-induced deprotonation reactions, the SPOS-PSCs exhibit favorablelongstability than the SnO2-PSCs. This work demonstrates that the surface reconstruction of the ETL is crucial for enhancing the power conversion efficiency and stability of PSCs.

Enhancing perovskite solar cell efficiency to 28.17% by Integrating Dion-Jacobson 2D and 3D phase perovskite Absorbers

Efficiency of power conversion for both kinds of inorganic as well as organic perovskites-based cells has increased in the last few years. To overcome this stability-related issue of 3D perovskite cells,2D perovskite has become an alternative option.The structure and the device, both are destabilized by the weak interactions observed in between the layers of the layered perovskite since the Ruddlesden Popper (RP) phase of 2D perovskite has a weak Van der Waal gap present in between the monoammonium cation layer.The PCE of perovskite cells has risen to 25 %. Commercialization of perovskites on a large scale as solar is a challenging task because lead is toxic.Keeping the toxic property of lead in mind we have used FTO (window layer)/TiO2(ETL)/(PDA)(MA)n-1PbnI3n+1(absorber layer)/Csx(FA0.4MA0.6)1-xPbI2.8Br0.2(absorber layer)/ spiro-OMeTAD (HTL).It has been observed that the DJ and RP phases of 2D PSC are individually found much more stable than their 3D counterpart used for perovskite-based solar cells. DJ and RP are merged to become proof of the efficiency as well as environmental stability of 2D perovskite-based solar cells.Several material parameters that affect the performance result obtained from the device,like the electron transport layer(ETL), hole transport layer(HTL), the thickness of the absorbing layer,etc were considered,studied,and also have been optimized.

A novel dual functional gradient Zn(O,S)/Mg electron-selective contact for dopant‐free silicon solar cells with efficiencies approaching 21 %

Dopant-free carrier-selective contacts have the potential to mitigate or eliminate parasitic absorption, auger recombination losses, etc. Therefore, the vigorous development of dopant-free carrier-selective contact materials is an important way to enhance the performance of crystalline silicon (c-Si) photovoltaics. This study presents the concept of magnetron sputtering gradient deposited zinc oxide (Gd-Zn(O,S)) combined with a low work function magnesium metal layer. Subsequently, the Gd-Zn(O,S)/Mg bifunctional layer was further investigated and optimised to determine its suitability as a contact layer for electron transfer in c-Si solar cells. This strategy simultaneously enables a good passivation and a low contact resistance. The c-Si(n)/a-Si:H(i)/Gd-Zn(O,S)/Mg devices are constructed and achieved an optimal contact recombination current density (J0) of approximately 1.51 fA cm−2, along with a minimum ρc of approximately 35.89 mΩ.cm2. As a consequence, the power conversion efficiency of a prototype silicon heterojunction solar cell is 20.92 %. This study demonstrates that the strategy of replacing the a-Si:H(n) electron transport layer with Gd-Zn(O,S) is an effective approach for improving the SHJ cell. This study also provides new perspectives for designing novel dopant-free carrier-selective contact structures.

Exploring the theoretical potential of tungsten oxide (WOx) as a universal electron transport layer (ETL) for various perovskite solar cells through interfacial energy band alignment modulation

Perovskite solar cells (PSCs) play a pivotal role in advancing renewable energy to achieve United Nation's Sustainable Development Goal 7 (SDG 7), which aims to ensure universal access to affordable, sustainable, reliable and modern energy services. Aiming to enhance the performance of PSCs by replacing the typically used electron transport layers (ETLs: TiO2, SnO2, ZnO etc.), we theoretically investigated the viability of tungsten oxide (WOX) as a promising ETL for PSCs. Moreover, the effect of altering the energy levels of WOX on cell performance has also been analyzed through simulation. Initially, 12 (twelve) PSC structures having the combination of different perovskite (PSK: CsPbBr3, CsPbI3, FAPbBr3, FAPbI3) absorber layers with different organic hole transport layers (HTLs: Spiro-OMeTAD, P3HT, PEDOT:PSS) and a fixed ETL of WOX were optimized numerically for comparing their performance. As CsPbBr3-based PSCs showed the best performance, further simulations were performed by varying some WOX/CsPbBr3 interface properties such as interface defect density, conduction band offset (CBO) between WOX and CsPbBr3, energy bandgap (Eg) of WOX etc. Finally, the best-performed PSCs were found for the Eg = 3.5 eV of WOX and the CBO of - 0.5 eV confirming the conduction band minimum (CBM) of WOX is lower than that of CsPbBr3 by 0.5 eV. A properly chosen WOX layer enhanced the efficiency of CsPbBr3-based PSCs up to 14.65 %, 14.52 % and 16.09 %, aproaching the Shockley-Queisser (S-Q) limit (16.37% for CsPbBr3-based solar cell) from the initial values of 11.39 %, 11.27 %, and 12.49 %, respectively. This study ensures WOX is a promising ETL for which a proper PSC structure having a suitable PSK and an HTL can improve cell performance. Moreover, the importance of modifying energy levels of ETL material in enhancing the performance of PSCs is explored. As a result, this study opens a path for the researchers to develop WOX having suitable CBM and Eg, so that it can be well-suited with a properly matched PSK material resulting in enhanced cell performance.

Enhancing Efficiency and Stability of Inverted Perovskite Solar Cells through Solution-Processed and Structurally Ordered Fullerene.

The electron transporting layer (ETL) used in high performance inverted perovskite solar cells (PSCs) is typically composed of C60, which requires time-consuming and costly thermal evaporation deposition, posing a significant challenge for large-scale production. To address this challenge, herein, we present a novel design of solution-processible electron transporting material (ETM) by grafting a non-fullerene acceptor fragment onto C60. The synthesized BTPC60 exhibits an exceptional solution processability and well-organized molecular stacking pattern, enabling the formation of uniform and structurally ordered film with high electron mobility. When applied as ETL in inverted PSCs, BTPC60 not only exhibits excellent interfacial contact with the perovskite layer, resulting in enhanced electron extraction and transfer efficiency, but also effectively passivates the interfacial defects to suppress non-radiative recombination. Resultant BTPC60-based inverted PSCs deliver an impressive power conversion efficiency (PCE) of 25.3% and retain almost 90% of the initial values after aging at 85°C for 1500 hours in N2. More encouragingly, the solution-processed BTPC60 ETL demonstrates remarkable film thickness tolerance, and enables a high PCE up to 24.8% with the ETL thickness of 200 nm. Our results highlight BTPC60 as a promising solution-processed fullerene-based ETM, opening an avenue for improving the scalability of efficient and stable inverted PSCs.

Atom layer deposited TiO2 electron transport layer for silicon heterojunction solar cells to achieve high performance

Silicon/compound heterojunction (SCH) solar cells based on p-type and n-type c-Si wafers using atom layer deposition-TiO2 and low work function metal as the electron transport layer and rear electrode are fabricated. Efficiencies of 20.6 % and 21.6 % are achieved on p-type and n-type silicon solar cells, respectively. High Voc exceeding 700 mV have been realized on both kinds of Si wafers. Special attention has been paid to the SCH solar cells based on p-type c-Si wafers in which the TiO2 electron transport layer serves as the emitter. Carrier transport mechanisms and junction characteristics of the SCH solar cells are analyzed based on dark J-V measurement. The formation of a strong inversion layer at the Si surface region is determined, which implies the high Voc potential of the SCH solar cells based on p-type Si. An optical loss analysis is performed along with a possible solution to further improve the Jsc. The feasibility of TiO2 applied as an efficient electron transport layer (emitter) in p-type SCH solar cells with high performance has been showed.

A multifunctional interlayer between mesoporous TiO2 and perovskite for perovskite solar cells with high efficiency and stability

The industrialization of the perovskite solar cells (PSCs) requires further lifting their power conversion efficiency (PCE). There are some important factors to hinder the PCE improvement, such as interface defects and energy level mismatching betwee electron transport layer (ETL) and perovskite layer, and solar energy loss due to no absorption of near infrared (NIR) for the perovsktie. Thus in this study, a multifunctional material of W-Er-Yb doped TiO2 (W-UC-TiO2) was prepared and applied to PSCs as an interlayer between mesoporous TiO2 and perovskite. The experimental results demonstrate that the interlayer of W-UC-TiO2 has the functions of improving NIR absorption for PSCs, passivating inerface defects and improving energy level matching between TiO2 and perovskite. A high efficiency of 21.32% was acquired for the PSCs with W-UC-TiO2 interlayer from 19.26% for the control device. Moreover, stability of the PSCs was improved by the insertion of W-UC-TiO2 interlayer.

Effect of magnesium doping on NiO hole injection layer in quantum dot light-emitting diodes

Abstract This study reports on the fabrication of quantum dot light-emitting diodes (QLEDs) with an ITO/Ni1−x Mg x O/SAM/TFB/QDs/ZnMgO/Al structure and investigates the effects of various Mg doping concentrations in NiO on device performance. By doping Mg into the inorganic hole-injection layer NiO (Ni1−x Mg x O), we improved the band alignment with the hole-injection layer through band tuning, which enhanced charge balance. Optimal Mg doping ratios, particularly a Ni0.9Mg0.1O composition, have demonstrated superior device functionality, underscoring the need for fine-tuned doping levels. Further enhancements were achieved through surface treatments of Ni0.9Mg0.1O with UV-Ozone (UVO) and thermal annealing (TA) of the ZnMgO electron transport layer. Consequently, by optimizing Mg-doped NiO in QLED devices, we achieved a maximum external quantum efficiency of 8.38 %, a brightness of 66,677 cd/m2, and a current efficiency of 35.31 cd/A, indicating improved performance. The integration of Mg-doped NiO into the QLED structure resulted in a device with superior charge balance and overall performance, which is a promising direction for future QLED display technologies.

Theoretical insight on electronic and optical properties of some phosphorescent iridium(III) complexes for organic light-emitting diode devices

Organic light-emitting diode (OLED) structures have been extensively investigated because of their potential applications in various fields. It is known that organic or metal-mediated organic compounds are used in the layers of OLEDs. Within OLED materials, iridium(III) compounds have attract much attention owing to their many advantages. Therefore, we predicted the OLED behaviors of twenty-five phosphorescent iridium(III) complexes using theoretical chemical methods. All theoretical calculations were performed with the B3LYP hybrid functional using Gaussian 16 and Amsterdam Modeling Suite 2023 programs. While the 6–31G(d) basis set for non-metal atoms and LANL2DZ basis set for iridium metal was preferred in the computations carried out by using Gaussian program, whereas in the calculations performed with the Amsterdam Modelling Suite program, the TZP basis set was used for all atoms. From the theoretically obtained results, it is seen that Ir6, Ir7, Ir22-Ir25 complexes can be proposed as good candidate for hole injection layer materials in OLED based on indium tin oxide as an anode. Within complexes investigated, it has been determined that Ir16 and Ir17 complexes are the most suitable candidates for electron transport layer materials, whereas Ir16 complex can be used as both a hole transfer layer and ambipolar materials. Furthermore, it has been predicted that Ir4, Ir7, Ir8, and Ir23 complexes could be preferred as hole blocking layer compounds. From the detailed analysis of the singlet-triplet transitions of the complexes studied, it could be said that all iridium(III) complexes investigated could be used as highly efficient phosphorescent OLED molecules.

Heterovalent Samarium Cation‐Doped SnO2 Electron Transport Layer for High‐Efficiency Planar Perovskite Solar Cells

Tin oxide (SnO2) has demonstrated significant potential as an electron transport layer (ETL) owing to its low‐temperature processing in perovskite solar cells (PSCs). However, the poor energy‐level alignment and the presence of interface defects between the SnO2 and perovskite layer aggravate the power conversion efficiency (PCE) of the PSCs. Herein, heterovalent samarium cation (Sm3+) is deliberately doped into SnO2, optimizing the energy‐level alignment between SnO2 and the perovskite layer, and effectively passivating the oxygen vacancy defects on the surface of SnO2. Experimental and theoretical conclusions reveal that Sm‐doping successfully passivates the defects in the ETL and improves the perovskite crystal quality, thereby reducing interface charge recombination, and enhancing electron extraction from perovskite to the SnO2 layer. Consequently, the optimized Sm‐doped SnO2‐based PSCs achieve a PCE of 24.10% with a VOC of 1.174 V, negligible hysteresis, and improved durability under ambient conditions.

Machine learning driven performance for hole transport layer free carbon-based perovskite solar cells

The rapid advancement of machine learning (ML) technology across diverse domains has provided a framework for discovering and rationalising materials and photovoltaic devices. This study introduces a five-step methodology for implementing ML models in fabricating hole transport layer (HTL) free carbon-based PSCs (C-PSC). Our approach leverages various prevalent ML models, and we curated a comprehensive dataset of 700 data points using SCAPS-1D simulation, encompassing variations in the thickness of the electron transport layer (ETL) and perovskite layers, along with bandgap characteristics. Our results indicate that the ANN-based ML model exhibits superior predictive accuracy for C-PSC device parameters, achieving a low root mean square error (RMSE) of 0.028 and a high R-squared value of 0.954. The novelty of this work lies in its systematic use of ML to streamline the optimisation process, reducing the reliance on traditional trial-and-error methods and providing a deeper understanding of the interdependence of key device parameters.

Boosting the performance of SnSe-based solar cells through electron and hole transport layers: A qualitative study and perspectives

The SnSe compound is garnering considerable interest as a potential solar absorber for developing highly efficient thin-film solar cells. Using one experimental report as a foundation and employing the one-dimensional solar cell capacitance simulator (SCAPS-1D), we examined the elements that impact the efficiency of solar cells utilizing tin selenide as the base material. The base structure consists of Anode/SnSe/CdS/i-ZnO/ZnO:Al/Cathode. A 0.5 μm thick SnSe film demonstrated an efficiency of 2.51 %. In the initial phase, we optimized the device efficiency to 18.65 % through parameter adjustments, utilizing toxic CdS as a buffer layer. In the subsequent phase, earth-abundant and non-toxic Zn1-xMgxO, SnO2, and TiO2 alternatives were explored as electron transport materials (ETL) to replace CdS. Zn1-xMgxO (with x = 0.1875) exhibited the highest efficiency at 19.03 %. In the final phase, various hole transport materials (HTL) were studied to enhance the SnSe-based solar cell's performance. Among the HTL materials investigated, NiO yielded the best efficiency of 20.59 % when using Zn1-xMgxO (with x = 0.1875) as a buffer layer.

ZnO/SrTiO3, ZnO/WO3, and ZnO/Zn2SnO4 Bilayer as Electron Transport Layers for Lead Sulfide Colloidal Quantum Dots Solar Cells.

In order to enhance the overall efficiency of colloidal quantum dots solar cells, it is crucial to suppress the recombination of charge carriers and minimize energy loss at the interfaces between the transparent electrode, electron transport layer (ETL), and colloidal quantum dots (CQDs) light-absorbing material. In the current study, ZnO/SrTiO3(STO), ZnO/WO3(TO), and ZnO/Zn2SnO4(ZTO) bilayers are introduced as an ETL using a spin-coating technique. The ZTO interlayer exhibits a smoother surface with a root-mean-square (RMS) value of ≈ 3.28nm compared to STO and TO interlayers, which enables it to cover the surface of the ITO/ZnO substrate entirely and helps to prevent direct contact between the CQDs absorber layer and the ITO/ZnO substrate, thereby effectively preventing efficient charge recombination at the interfaces of the ETL/CQDs. Furthermore, the ZTO interlayer possesses superior electron mobility, a higher visible light transmission, and a suitable energy band structure compared to STO and TO. These characteristics are advantageous for extracting charge carriers and facilitating electron transport. The PbS CQDs solar cell based on the ITO/ZnO/ZTO/PbS-FABr/PbS-EDT/NiO/Au device configuration exhibits the highest efficiency of 15.28%, which is significantly superior than the ITO/ZnO/PbS-FABr/PbS-EDT/NiO/Au solar cell device (PCE = 14.38%). This study is anticipated to offer a practical approach to develop ultrathin and compact ETL for highly efficient CQDSCs.

Numerical investigation and design optimization for enhanced efficiency of Cs2AgBiBr6 perovskite solar cell

Nowadays, environmental concerns are becoming increasingly important. As a result of the imperative to protect society, lead-free perovskites are becoming increasingly important. The lead-free compound cesium silver bismuth bromide (Cs2AgBiBr6) was numerically investigated as a potential candidate for double perovskite solar cells application. In the proposed architecture, we combine FTO/ETL-SnO2/Cs2AgBiBr6/HTL-CuI/Au, all optimized for performance. To optimize the solar cell’s performance, the device configuration was modelled using SCAPS-1D. An evaluation of the impact of various factors, including absorber thickness, defect density, electron affinity, electron and hole transport layer optimization, band diagram analysis, working temperature and quantum efficiency, was conducted. The proposed device configuration exhibited excellent photovoltaic performance, achieving a PCE of 8.15%, a Voc of 1.041 V, a Jsc of 11.79 mA cm−2, an FF of 66.41%, and a quantum efficiency of 99.19% within the visible range. This research highlights the potential of Cs2AgBiBr6 as a promising perovskite material for use in lead-free photovoltaic technology.

Performance evaluation of inorganic Cs3Bi2I9-based perovskite solar cells with BaSnO3 charge transport layer

This research embedded with a novel idea of integration of perovskite material as charge transport layer corresponding to the perovskite absorber layer. The study explores the effectiveness of BaSnO3 perovskite material as an electron transport layer (ETL) in Cs3Bi2I9-based perovskite solar cells, using SCAPS-1D simulations. The research meticulously examines how structural and optical variations in each layer affect the device’s performance indicators, finding the thickness of the Cs3Bi2I9 layer and its defect concentration pivotal for optimal functionality. The highest photovoltaic efficiency, 20.62%, was achieved with an absorber layer thickness of 0.8 micrometers and acceptor and donor concentrations between 1E17 /cm3 and 1E18 /cm3, respectively. The absorber’s bulk defect density optimally ranged from 1E14 /cm3 to 1E15 /cm3. Interface defects between BaSnO3 and Cs3Bi2I9 layers significantly influenced performance, more so than those at the HTL (Cu2O) interface. The study also assesses thermal effects and series and shunt resistances, aiming to mitigate potential induced degradation (PID), a key concern for solar cell longevity and reliability. Nickel (Ni) was chosen as the back contact metal, balancing cost and efficiency. This research intends to clarify PID conditions to enhance the durability and consistent performance of photovoltaic systems.

Resolving the Trap Distribution of Chalcogenide-Based Heterojunctions via Optical Injection Deep Level Transient Spectroscopy.

Chalcogenide semiconductors have emerged as promising candidates for next-generation optoelectronics, mainly benefiting from their cost-effective processability, chemical versatility, and excellent stability. However, the device performance is limited by the complex defect characteristics, necessitating a detailed understanding of the defect density, types, and distribution. This study employs optical injection deep level transient spectroscopy to characterize the trap features of antimony bismuth sulfide-based heterojunctions. Photoexcitation offers the possibility to determine the spatial distribution of traps. It reveals distinct distributions of hole and electron traps. Short-wavelength light (570 nm) detects hole traps near the hole transport layer, while long-wavelength light (830 nm) identifies electron traps near the electron transport layer. Additional intermediate-wavelength tests (670 and 755 nm) and light field distribution simulation further elucidate the trap distribution. Transient absorption and transient photocurrent also support the non-uniform trap distribution within the chalcogenide-based photodiodes.

Current matching and filtered spectrum analysis of wide-bandgap/narrow-bandgap perovskite/CIGS tandem solar cells: A numerical study of 34.52 % efficiency potential

Perovskite (PVK) materials with wide-bandgap (WBG) play a crucial role in achieving high-performance tandem devices but phase segregation and open-circuit voltage (VOC) loss hinders in surpassing the efficiency of single-junction solar cells. Present work discloses a numerical simulation which has been carried out using a WBG material CH3NH3PbI3-xClx of bandgap (Eg) 1.65eV as an absorber layer of the top cell (TCELL) and a Cu(In,Ga)Se2-based cell having narrow-bandgap (NBG) of Eg (1.27eV) has been used as bottom cell (BCELL). The TCELL utilizes polyethyleneimine ethoxylated (PEIE) interfacial layer to promote charge-collection and charge-tunneling. The TCELL and BCELL have been optimized by various optimization processes such as simultaneous thickness variation of active-region with defect density (DD), variation of interface defect density (IDD) with solar-cell parameters a commendable power conversion efficiency (PCE) of 27.06 %, and 26.77 % has been achieved for respective solar-devices. Variations of numerous electron transport layer (ETL) and hole transport layer (HTL) have also been performed to acquire highly optimized TCELL. Thus, a perovskite/CIGS tandem solar cell (PVK/CIGS-TSC) device has been obtained using filtered-spectra analysis and current-matching (method which display a promising photovoltaic (PV) parameter with a high VOC of 2.29 V, short-circuit current density (JSC) of 17.41 mA/cm2, fill factor (FF) of 86.45 % and PCE of 34.47 %. These discoveries hold significant promise for the future development of TSCs.

Rapid oxygen plasma treatment of tin oxide layers for improving the light stability of perovskite solar cells

Surface treatment of SnO2 as an electron transport layer is essential for improving charge transport and device performance in the fabrication of perovskite solar cells. In this study, oxygen plasma with a controlled ion–radical composition ratio was used for rapid surface treatment to clean the surface of SnO2, and its performance was compared with that of the conventional UV–ozone treatment. Consequently, the plasma treatment succeeded in increasing the processing speed up to 40 times faster than that required for the conventional UV–ozone pretreatment. Furthermore, plasma pretreatment improved the photostability of solar cells.