Hole Transport Layer Research Articles

Achieving 32.9% efficiency in Pb-Based quantum dot solar cells via SCAPS-1D simulation optimization

Abstract This study presents a comprehensive investigation and in-depth analysis of the optimization of Pb-based quantum dot solar cells (QDSCs), concentrating on the influences of doping concentration, absorber layer thickness, defect density, temperature, and resistive elements. We systematically examined three absorber materials: lead sulfide (PbS), tetrabutylammonium iodide-treated PbS (PbS-TBAI), and lead selenide (PbSe) quantum dots (QDs). Optimal doping concentrations of 1 × 10 17 cm−3 for PbS and 1 × 10 22 cm−3 for both PbS-TBAI and PbSe were identified. Our findings reveal that precise control of these parameters can significantly enhance power conversion efficiency (PCE), achieving values of 24.6%, 28%, and 26.2% for PbS, PbS-TBAI, and PbSe, respectively. Additionally, we investigated the impact of absorber layer thickness on device performance. We discovered that a 1 µm thickness for PbS yields a maximum PCE of 32.9% due to balanced photon absorption and reduced Shockley–Read–Hall recombination. Conversely, PbSe’s performance declined with increased thickness because of its layer-dependent bandgap. We found that lower defect densities ( 1 × 10 14 cm−3) critically improve PCE and fill factor across all materials. The temperature-dependent studies demonstrated that PbS-TBAI exhibits remarkable resilience, maintaining efficiency under thermal stress due to effective surface passivation. Analyses of series and shunt resistances highlighted the importance of minimizing internal resistances to optimize device performance. The proposed device structure comprises a fluorine-doped tin oxide front contact layer, a silver sulfide (Ag2S) electron transport layer, the QD absorber layer (PbS, PbS-TBAI, or PbSe), and copper(I) oxide (Cu2O) hole transport layer. Utilizing cascade band alignment, we achieved a record PCE of 32.9%. This research highlights the significant potential of Pb-based QDSCs for achieving high efficiencies through promising material and structural optimization, positioning them as competitive candidates for next-generation solar technologies. The results provide a valuable understanding of designing high-performance QDSCs, paving the way for their integration into sustainable energy solutions.

Active Locating Exciton- and Charge-Initialized Degradation in Quantum-Dot Light-Emitting Diodes.

For quantum-dot light-emitting diodes (QLED), electrical aging commonly introduces collective aging sources across all layers, making it difficult to isolate the impact of each layer on electroluminescence (EL) degradation. In this work, a layer-selective aging method using active photoexcitation is proposed, in which the photoexcitation wavelength is used to selectively target specific layers for exciton generation, and an electrical bias is applied to induce photocurrent and create charges. An iterative aging-sampling (A-S) procedure is used to link aging conditions to EL degradation. It is found that photo-aging leads to strong but reversible quenching of EL intensity, which is interpreted as being caused by electrical field screening due to trapped charges in the quantum dot (QD) layer and requires electrical activation before the sampling (S) step. Repeated A-S cycles in a model red QLED system show that excitations in the QD layer result in negligible EL degradation. In contrast, aging of the hole-transport (HT) layer enables an acceleration of aging rate by 3 orders of magnitude compared to standard aging and is interpreted as a result of photo-charge accumulation in the HT layer, particularly related to electrons and low electron mobility.

Theoretical evaluation of the realizable power conversion efficiency and the possible scheme for hole-transport-layer-free carbon-cathode CsPbI2Br solar cells

Abstract Hole-transport-layer (HTL)-free carbon-cathode CsPbI2Br solar cells have gained notable attention because of the good balance between light absorption and improved stability, as well as the cost advantage. However, the power conversion efficiency (PCE) experimentally realized for the related solar cells of < 16% is necessarily improved for possible practical application. In this study, the impact of the interfacial defect density between CsPbI2Br and the carbon cathode that is one of the most pivotal factors influencing the PCE improvement is studied, and meanwhile a feasible scheme using a thin AlOx passivation layer to block electrons and allow hole tunneling is proposed. The PCE of 19.68% is predicted for HTL-free carbon-cathode CsPbI2Br solar cells.

Modification of the Se/MoOx Rear Interface for Efficient Wide-Band-Gap Trigonal Selenium Solar Cells.

Trigonal selenium (t-Se) is a promising wide-band-gap photovoltaic material with a high absorption coefficient, abundant resources, simple composition, nontoxicity, and a low melting point, making it suitable for absorbers in advanced indoor and tandem photovoltaic applications. However, severe electrical losses at the rear interface of the t-Se absorber, caused by work function and lattice mismatches, limit the voltage output and overall performance. In this study, a strategy to enhance carrier transport and collection by modifying interfacial chemical interactions is proposed. By applying a controlled heat process during the deposition of the MoOx hole transport layer, a chemical interaction at the t-Se/MoOx interface can be facilitated. This results in the formation of an interfacial MoSex layer, leading to improved valence band alignment and reduced barrier and recombination losses. As a result, the performance of t-Se thin-film solar cells is improved compared to those without the heating process.

Efficient hole extraction by doped-polyaniline/graphene oxide in lead-free perovskite solar cell: a computational study

Abstract The intriguing behavior of doped polyanilinine/graphene oxide (PANI/GO) offers a solution to the pivotal problem of device stability against moisture in perovskite solar cell (PSC). Tunable bandgap formation of doped PANI/GO with an absorber layer allows effective flexibility for charge carrier conduction and reduced series resistance further boosting the cell performance. Herein, the L9 Orthogonal Array (OA) Taguchi-based grey relational analysis (GRA) optimization was introduced to intensify the key output responses. Furthermore, this work also delved into incorporating a Pb-free absorber perovskite layer, formamidinium tin triiodide (FASnI3), and concomitantly eluding the environmentally hazardous substance. The numerical optimization supported by statistical analysis is based on experimental data to attain the utmost peak cell efficiency. Taguchi’s L9 OA-based GRA predictive modeling recorded over one-fold enhancement over experimental results, reaching as high as 20.28% power conversion efficiency (PCE). Despite that, the PCE of the structures is severely affected by interface defects at the electron transport layer/absorber (ETL/Abs) vicinity, which is almost zero at merely 1 × 1014 cm−2, manifesting that control measures need to be taken into account. This work deduces the feasibility of ETL/Abs stack structure in replacing the conventional Pb-based perovskite absorber layer, while maximizing the potential use of doped PANI/GO as a hole transport layer (HTL).

PEROVSKITE SOLAR CELLS AND THEIR TYPES

Perovskite photovoltaic compartments have garnered momentous consideration in photovoltaics owing to their easy manufacturing process and high efficiency. The optoelectronic properties of perovskite solar cells (PSCs), made from halide and diverse-halide materials, are exceptional. Perovskite structures exhibit remarkable stability despite a wide band gap and minimal charge transfer. Some advantages of perovskite solar cells are; high efficiency, low cost, rapid manufacturing, flexibility, energy payback time, sustainability, etc. To address these challenges, multidimensional perovskite materials are utilized to achieve long-term stability and good performance. Recent advancements in low-temperature synthesis methods and improved contact and electrode components have resulted in PSCs surpassing an efficiency of 25%. Perovskites' characteristics can also be enhanced by altering their elemental makeup. The light-harvesting perovskite material, the electron-transporting layer (ETL), the transparent conductive oxide (TCO) film, the hole-transporting layer (HTL), and the metal contact material. The most fantastic and popular perovskite material for sunny collecting at the moment is MAPbI3. Compared to the conventional MAPbI3 perovskite, additional perovskite substances, for example, assorted halide-assorted cation, hybrid cation, and hybrid halide, are drawing more interest. This paper mainly discussed metal-based PSCs, non-metal-based PSCs, and polymer-based PSCs. Moreover, there has been a significant focus on the constancy and production concerns that boundary the commercialization and modularization of perovskite solar cubicles.

Natural Dextran as an Efficient Interfacial Passivator for ZnO‐Based Electron‐Transport Layers in Inverted Organic Solar Cells

AbstractCompared to conventional organic solar cells (OSCs) with acidic PEDOT:PSS as the hole transport layer (HTL), inverted OSCs (i‐OSCs) with zinc oxide (ZnO) as the electron transport layer (ETL) display significant advantages in terms of high stability. However, an obvious limitation in i‐OSCs is that the sol‐gel processed ZnO layers possess detrimental defects at the interface, which hinders the improvement of its photovoltaic performance. To address this problem, a natural, and green dextran (Dex) is used as an efficient interfacial passivator to modify the ZnO layer, thereby achieving enhanced device performance in i‐OSCs. The introduction of the Dex passivator efficiently suppresses the interfacial recombination loss, resulting in higher power conversion efficiencies (PCEs). Interestingly, Dex‐passivated ZnO exhibits broad applications as an ETL for different types of i‐OSCs, including fullerene, non‐fullerene, and all‐polymer OSCs, in which the D18:Y6 system gives the highest PCE of 18.32%. This is one of the highest values reported for binary i‐OSCs. Moreover, the application of Dex significantly improves the device stability, and the T80 lifetimes based on PM6:Y6, D18:Y6, and PM6:PY‐IT exceed 1500 h. These results imply that Dex is an excellent interfacial passivator for ZnO‐based ETL for high‐efficiency and stable i‐OSCs.

Promoting Exciton Dissociation and Hot Hole Extraction via Hole Transport Layer Engineering Enable Highly Efficient Perovskite Solar Cells With 25.51% Efficiency

AbstractEffective exciton dissociation and hot hole extraction in the perovskite layer is of significance for achieving high‐performance perovskite solar cells (PSCs), however, the impact of the hole transport layer (HTL) on the two issues is often ignored. Herein, for the first time, an organic semiconductor (WL) is introduced into the well‐known Spiro‐OMeTAD to afford two different HTLs (Spiro‐OMeTAD, Spiro‐OMeTAD+WL), which allows this to experimentally explore the dynamics process. We found that WL incorporation can significantly enhance hole transport ability and the built‐in electric field of Spiro‐OMeTAD+WL‐based HTL, which helps to promote the exciton dissociation of the perovskite layer. At the same time, transient absorption spectroscopy studies unambiguously demonstrate that the Spiro‐OMeTAD+WL‐based HTL exhibits almost two times higher extraction efficiency of hot holes than that of the control Spiro‐OMeTAD. Thus, the enhanced exciton dissociation and hot hole extraction can result in the reduced charge accumulation at the perovskite/HTL interface and suppressed charge‐carrier recombination in the device. Consequently, the WL‐based device shows significantly enhanced power conversion efficiency from 22.35% to 25.51%. The findings of this work can provide some valuable insights for improving PSCs efficiency in the near future.

A Versatile Ionic Liquid Additive for Perovskite Solar Cells: Surface Modification, Hole Transport Layer Doping, and Green Solvent Processing.

Hole-transport layers (HTL) in perovskite solar cells (PSCs) with an n-i-p structure are commonly doped by bis(trifluoromethane)sulfonimide (TFSI) salts to enhance hole conduction. While lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) dopant is a widely used and effective dopant, it has significant limitations, including the need for additional solvents and additives, environmental sensitivity, unintended oxidation, and dopant migration, which can lead to lower stability of PSCs. A novel ionic liquid, 1-(2-methoxyethyl)-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (MMPyTFSI), is explored as an alternative dopant for 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamino)-9,9'-spirobifluorene (spiro-OMeTAD). MMPy ions act as a surface passivator, reducing defects on the perovskite surface, while TFSI ions facilitate p-type doping. MMPyTFSI functions as an efficient dopant, maintaining excellent performance even when tetrahydrofuran (THF) is utilized as a solvent in place of chlorobenzene (CB), while significantly reducing the environmental impact of the process. The optimized PSC achieves a power conversion efficiency (PCE) of 23.10% and demonstrates enhanced long-term stability in all aging tests for over 1000 h in a humid atmosphere, at high temperature, and under simulated sunlight illumination. These results demonstrate that MMPyTFSI is an effective and environmentally friendly dopant for producing stable and efficient PSCs.

Operando spin observation elucidating performance-improvement mechanisms during operation of Ruddlesden–Popper Sn-based perovskite solar cells

Sn-based perovskite solar cells (PSCs) have attracted attention because of their low environmental impact. Unfortunately, the readily occurring oxidation of Sn2+ inhibits further improvement of their efficiency and stability. Ruddlesden–Popper (RP) Sn-based perovskites are considered promising candidates as absorbers that improve the performance and stability of Sn-based PSCs. However, microscopic understanding of performance-enhancing mechanisms remains insufficient. For this study, electron spin resonance (ESR) spectroscopy measurements were taken of RP Sn-based PSCs with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole-transport layers and (BA0.5PEA0.5)2FA3Sn4I13 perovskite layers to clarify the space-charge region formation mechanism at the PEDOT:PSS/(BA0.5PEA0.5)2FA3Sn4I13 interface. These results indicated electron-barrier formation in the (BA0.5PEA0.5)2FA3Sn4I13 layer near the PEDOT:PSS layer. Moreover, the electron barrier was found to be enhanced during device operation. The enhanced interface band bending reduces interface recombination and thereby improves the device's performance. These findings might provide important progress in practical applications of PSCs and might advance the realization of a carbon-neutral society.

Anchorable Polymers Enabling Ultra-Thin and Robust Hole-Transporting Layers for High-Efficiency Inverted Perovskite Solar Cells.

Currently, the development of polymeric hole-transporting materials (HTMs) lags behind that of small-molecule HTMs in inverted perovskite solar cells (PSCs). A critical challenge is that conventional polymeric HTMs are incapable of forming ultra-thin and conformal coatings like self-assembly monolayers (SAMs), especially for substrates with rough surface morphology. Herein, we address this challenge by designing anchorable polymeric HTMs (CP1 to CP5). Specifically, coordinative pyridyl groups are introduced as side-chains on poly-triarylamine (PTAA) backbone with varied contents by copolymerization method, resulting in chemical interactions between polymeric HTMs and substrates. The strong interaction allows them to be processed into ultra-thin, uniform, and robust hole-transporting layers through employing low-concentration solutions (0.1 mg mL-1, vs. 2.0-5.0 mg mL-1 for conventional PTAA), greatly decreasing charge transport losses. Moreover, upon systematically tuning the pyridyl substitution ratio, the energy levels, surface wetting, solution processability, and defect passivation capability of such anchorable HTMs are simultaneously optimized. Based on the optimal CP4, we achieved highly efficient inverted PSCs with power conversion efficiencies (PCEs) up to 26.21 %, which is on par with state-of-the-art SAM-based inverted PSCs. Furthermore, these devices exhibit enhanced stabilities under repeated current-voltage scans and reverse bias ageing compared with SAM-based devices.

Optimizing the Hole-Transport Layer with Ammonium Thiocyanate for Enhanced Performance in Lead-Free Perovskite Light-Emitting Diodes

Optimizing the Hole-Transport Layer with Ammonium Thiocyanate for Enhanced Performance in Lead-Free Perovskite Light-Emitting Diodes

Computational Study of Chalcogenide-Based Perovskite Solar Cell Using SCAPS-1D Numerical Simulator

Perovskite solar cells (PSCs) are regarded as extremely efficient and have significant potential for upcoming photovoltaic technologies due to their excellent optoelectronic properties. However, a few obstacles, which include the instability and high costs of production of lead-based PSCs, hinder their commercialization. In this study, the performance of a solar cell with a configuration of FTO/CdS/BaZrS3/HTL/Ir was optimized by varying the thickness of the perovskite layer, the hole transport layer, the temperature, the electron transport layer (ETL)’s defect density, the absorber defect density, the energy band, and the work function for back contact. Various hole transport layers (HTLs), including Cu2O, CuSCN, P3HT, and PEDOT:PSS, were assessed to select the best materials that would achieve high performance and stability in PSC devices. At optimal levels, PEDOT:PSS reached a maximum power conversion efficiency (PCE) of 18.50%, while P3HT, CuSCN, and Cu2O exhibited a PCE of 5.81, 10.73, and 9.80%, respectively. The high performance exhibited by PEDOT:PSS was attributed to better band alignment between the absorber and the PEDOT:PSS, and, thus, a low recombination of photogenerated charges. The other photovoltaic parameters for the best device were a short-circuit current density (Jsc) of 23.46 mA cm−2, an open-circuit voltage (Voc) of 8.86 (V), and a fill factor (FF) of 8.90%. This study highlights the potential of chalcogenide-based PSCs as an efficient and stable alternative to traditional lead-based solar cells, with successful optimization paving the way for future research on eco-friendly materials and scalable production methods.

Perovskite Solar Cells, Featuring a Double Layer of FAPbI3 and MAPbI3, with CsSnI3 as the Hole Transport Layer, Achieved Remarkable Efficiency and Stability of 28.06%

Perovskite Solar Cells, Featuring a Double Layer of FAPbI3 and MAPbI3, with CsSnI3 as the Hole Transport Layer, Achieved Remarkable Efficiency and Stability of 28.06%

Theoretical analysis and performance optimization of Cs<sub>2</sub>AgBiI<sub>6</sub> solar cells with dual hole transport layers

Double perovskite materials have received significant attention in the photovoltaic field due to their low cost, environmental friendliness, and lead-free composition, which make them ideal candidates for next-generation solar cell applications. In this work, the photovoltaic performance of solar cells using Cs<sub>2</sub>AgBiI<sub>6</sub> as the light-absorbing layer is systematically investigated through simulations using Silvaco ATLAS software. Based on the previously reported single hole transport layer device architecture, namely ITO/ZnO/Cs<sub>2</sub>AgBiI<sub>6</sub>/HTL/Au, a new dual hole transport layer structure ITO/ZnO/Cs<sub>2</sub>AgBiI<sub>6</sub>/HTL1/HTL2/Au is proposed. Different dual hole transport layer combinations are explored, and their influence on the internal physical mechanism and the device performance are analyzed and optimized in detail. The simulation results show that the devices using Cu<sub>2</sub>O/NiO and NiO/Si respectively as dual hole transport layer significantly improve charge extraction and generate a negative electric field at the interface, thereby reducing recombination losse and accelerating the transport of hole carriers. These two configurations exhibit substantially higher efficiencies than those configurations with a single hole transport layer, confirming the advantages of the dual hole transport layer structure. Additionally, devices using Cu<sub>2</sub>O/CZTS and MoO<sub>3</sub>/CZTS as dual hole transport layer show better performance than the reference structure using Spiro-OMeTAD/CZTS, indicating the potential for further improvement by optimizing material selection and layer properties. Of the various dual hole transport layer combinations tested, the structure utilizing Cu<sub>2</sub>O/CZTS achieves the highest simulated power conversion efficiency (PCE) of 22.85%. By optimizing the thickness of each functional layer, the efficiency can be further increased to 25.62%, and the optimal layer thickness is determined to be 40 nm for ZnO, 850 nm for Cs<sub>2</sub>AgBiI<sub>6</sub>, 140 nm for Cu<sub>2</sub>O, and 150 nm for CZTS. Furthermore, the effects of environmental and material parameters, such as temperature and hole transport layer doping concentration, on device performance are investigated. This study lays a theoretical foundation for the design and enhancement of double perovskite solar cells. By demonstrating the potential that the dual hole transport layer structures can significantly improve device efficiency, their value in advancing environmentally friendly and lead-free photovoltaic technologies becomes very prominent. The insights gained from this research pave the way for developing high-performance double perovskite solar cells with optimized architectures and material properties.

A Low-cost High-performance Dopant-free Phenyl-based Hole Transport Material assisted Efficient and Stable Perovskite Solar Cells

Perovskite solar cells (PSCs) with dopant‐free hole transporting layer (HTL) have been widely studied for their excellent photoelectric conversion efficiency and outstanding stability. However, the high production cost and complicated...

Modulating Mn-doped NiO nanoparticles: structural, optical, and electrical property tailoring for enhanced hole transport layers.

Mn-doped NiO nanoparticles (NPs), denoted as Ni1-x Mn x O with x values of 0.00, 0.02, 0.04, 0.06, and 0.08, were synthesized using a chemical precipitation process. These NPs were comprehensively analyzed for their structural, optical, and electrical properties, along with their surface morphology and elemental composition. X-ray Diffraction (XRD) confirmed the single-phase cubic crystal structure and revealed a reduction in crystallite size from 15.26 nm to 10.38 nm as Mn doping increased. Field Emission Scanning Electron microscopy (FE-SEM) determined the average particle sizes ranging from 26.03 nm to 23.30 nm. The optical properties, assessed by UV-visible spectroscopy (UV-vis), revealed a widening of the bandgap from 3.49 eV to 4.10 eV with increasing Mn doping, suggesting tunable optical characteristics. X-ray Photoelectron Spectroscopy (XPS) confirmed the presence of nickel (Ni), oxygen (O), and manganese (Mn) within the NPs. The highest mobility, 1.31 ± 0.03 × 103 cm2 V-1 s-1, was observed in the 6 wt% Mn-doped NiO NPs thin film, as determined by Hall measurements. To assess their practical utility, SCAPS-1D simulation was employed, demonstrating the potential of Mn-doped NiO NPs as a hole transport layer (HTL) in perovskite solar cells (PSCs). The enhanced electrical and optical properties, combined with structural tunability, highlight Mn-doped NiO as a promising material for advanced optoelectronic applications. This study provides valuable insights into the development of efficient and stable solar cells, offering a pathway to optimize material design for improved performance in photovoltaic applications.

High efficiency of solution-processed inverted organic solar cells enabled by an aluminum oxide conjunction structure

The lack of solution-processed hole transport layers (HTLs) has become an obstacle to not only developing all-solution-processed inverted organic solar cells (OSCs) but also enabling their full potential of high...

Numerical simulation for a suitable electron transport layer of a lead-free CuIn2Se3 based perovskite solar cell and PV module

The high expense of solar cell manufacture and experimentation has led researchers to use numerical simulation. The advantages of simulation-based optimization include the simplicity of use, low cost, and the ability to forecast the ideal parameters that go into producing a cell with the optimum performance. The efficiency of perovskite materials used in solar systems has increased significantly, and they are virtually ready for commercialization. Academics and the scientific community are now interested in lead-free perovskite materials because of the toxic problem and hazardous nature of lead (Pb)-based perovskite materials. In this research, Pb is replaced by copper indium diselinide (CuInSe2). This study simulated, examined, and analyzed the performance of photovoltaic (PV) CuInSe2-based TFSCs with three different electron transport layers: indium sulfide (In2S3), titanium dioxide (TiO2), and stannic oxide (SnO2). SCAPS-1D software was used to model (FTO/TiO2/CuInSe2/Spiro-OMeTAD/Ni), (FTO/SnO2/CuInSe2/Spiro-OMeTAD/Ni), and (FTO/In2S3/CuInSe2/Spiro-OMeTAD/Ni) configurations to determine which one has the highest conversion efficiency. All three electron transport layer (ETL) thicknesses, with absorber and hole-transport (HTL) layer thicknesses, were optimized. Results indicate that, the absorber layer for SnO2 and In2S3 layers must be 3.00µm thick, and for the TiO2 layer it must be 4.00µm thick. Efficiency of 26.17% is revealed with SnO2, whereas Jsc, Voc, and FF, are observed as 43.15mA/cm2, 0.723V, and 83.80%, respectively. While with In2S3, efficiency is revealed as 26.15%, with Jsc, Voc, and FF are observed as 43.17mA/cm2, 0.723V, and 83.68% respectively. Efficiency of 26.65% is revealed by TiO2 with current density (Jsc), open circuit voltage (Voc), and fill factor (FF), which are shown as 43.53mA/cm2, 0.728V, and 83.68%, respectively which was carefully calculated. The device shows highest performance with TiO2 ETL. The maximum extent for Jsc, Voc, FF%, and PCE% during optimal investigation is shown by the generation of supplemental electron-hole pairs under standard conditions by altering the thicknesses of the absorber, hole, and electron transport layers. Parasitic resistances effect on the cell performance indicate that solar cells work effectively with low Rs and high Rsh values. The temperature effect on solar cells shows that as temperature rises, cell performance declines due to increased reverse saturation current and reduced bandgap. Quantum efficiency analysis of three ETL layers found that TiO2 and SnO2 efficiency increased rapidly between 300–400nm, while In2S3 peaked at 300nm and then declined. Simulation results from SCAPS-1D were used to configure PVsyst software for a solar module with 72 cells (2.2 ×1.1m). Module performance and output power were evaluated based on temperature and sun irradiation variations using input from the solar capacitance simulator. The potential of CuIn2S3 as a perovskite material to produce toxicity-free renewable energy is demonstrated by this study.

Small molecule doped polymer hole transport layers for all solution processed inverted QLED with using green solvents

Small molecule doped polymer hole transport layers for all solution processed inverted QLED with using green solvents