PSS Hole Transport Layer Research Articles

Electrochemical deposition of NiO bunsenite nanostructures with different morphologies as the hole transport layer in polymer solar cells

• Electrodeposition of p-type nickel oxide (NiO) using anodic potentiostatic and cyclic voltammetry. • Applying both NiO as the hole transport layer (HTL) in the fabrication of polymer solar cells. • NiO synthesized by the anodic potentiostatic exhibited the best features as the HTL. • The best PSC showed J SC , V OC , FF , and PCE of 10.95 mA/cm 2 , 0.64 V, 0.60 and 4.21%, respectively. Hole transport layers (HTLs) are one of the most important components of bulk heterojunction polymer solar cells (BHJ PSCs), having functions of optimizing interface, adjusting the energy match, and helping obtain higher PCE. Inorganic p-type semiconductors are alternative HTLs due to their chemical stability, high mobility, high transparency, and applicable valence band (VB) energy level. In this work, interlayer engineering in BHJ PSC was performed using solution-processed p-type nickel oxide (NiO) as the HTL. NiO nanostructures were synthesized by anodic potentiostatic and cyclic voltammetry (CV) electrodeposition methods. Simple adjustment of the applied potential regime and electrodeposition parameters led to considerable structural and electrochemical changes in the resulting NiO. Eventually, the best sample was selected in terms of suitable surface conductivity, high optical transparency, and appropriate energy levels. NiO nanostructures with FCC crystal structure synthesized by anodic potentiostatic electrodeposition showed conductivity of 0.038 mS.cm -1 and charge mobility of 2.01 cm 2 .V -1 s -1 , respectively, about 30.2% and 24.8% higher than the NiO synthesized by CV. The anodic potentiostatic electrodeposition method increased the photovoltaic performance of the PSCs by 43% compared to the CV method. The average power conversion efficiencies for the anodic potentiostatic and CV methods were 2.95% and 4.21%, respectively. The PCE of these cells was about 13% and 62% higher than that considered for the reference device prepared based on the PEDOT:PSS HTL.

A Self‐Assembled Vertical‐Gradient and Well‐Dispersed MXene Structure for Flexible Large‐Area Perovskite Modules

AbstractAdvancing hole transport layers (HTL) to realize large‐area, flexible, and high‐performance perovskite solar cells (PSCs) is one of the most challenging issues for its commercialization. Here, a self‐assembled gradient Ti3C2Tx MXene incorporated PEDOT:PSS HTL is demonstrated to achieve high‐performance large‐area PSCs by establishing half‐caramelization‐based glucose‐induced MXene redistribution. Through this process, the Ti3C2Tx MXene nanosheets are spontaneously dispersed and redistributed at the top region of HTL to form the unique gradient distribution structure composed of MXene:Glucose:PEDOT:PSS (MG‐PEDOT). These results show that the MG‐PEDOT HTL not only offers favorable energy level alignment and efficient charge extraction, but also improves the film quality of perovskite layer featuring enlarged grain size, lower trap density, and longer carrier lifetime. Consequently, the power conversion efficiency (PCE) of the flexible device based on MG‐PEDOT HTL is increased by 36% compared to that of pristine PEDOT:PSS HTL. Meanwhile, the flexible perovskite solar minimodule (15 cm2 area) using MG‐PEDOT HTL achieve a PCE of 17.06%. The encapsulated modules show remarkable long‐term storage stability at 85 °C in ambient air (≈90% efficiency retention after 1200 h) and enhanced operational lifetime (≈90% efficiency retention after 200 h). This new approach shows a promising future of the self‐assembled HTLs for developing optoelectronic devices.

Boosting Performance of Inverted Perovskite Solar Cells by Diluting Hole Transport Layer.

In our study, by developing the diluted PEDOT:PSS (D-PEDOT:PSS) to replace PEDOT:PSS stock solution as hole transport layer (HTL) materials for fabricating the inverted perovskite solar cells (PSCs), the performance of developed device with ITO/D-PEDOT:PSS/MAPbI3-xClx/C60/BCP/Ag structure is enhanced distinctly. Experimental results reveal that when the dilution ratio is 10:1, the optimal power conversion efficiency (PCE) of the D-PEDOT:PSS device can reach up to 17.85% with an increase of 11.28% compared to the undiluted PEDOT:PSS device. A series of investigations have confirmed that the efficiency improvement is mainly attributed to the two aspects: on one hand, the transmittance and conductivity of D-PEDOT:PSS HTL are improved, and the density of defect states at the interface is reduced after dilution, promoting the separation and transmission of charges, thus the short-circuit current (JSC) is significantly increased; on the other hand, the work function of D-PEDOT:PSS becomes more consistent with perovskite layer, and the voltage loss is reduced, so that the higher open circuit voltage (VOC) is obtained. Our research has indicated that diluting HTL develops a simpler, more efficient and cost-effective method to further improve performance for inverted PSCs.

High-efficiency (over 33 %) indoor organic photovoltaics with band-aligned and defect-suppressed interlayers

In recent years, the emergence of the Internet of Things (IoT) has led to growing interest in the use of organic-based artificial light cells (OALCs; indoor organic photovoltaics) to harvest ambient light energy. This study employs atomic layer deposition (ALD)-processed vanadium oxide (V2O5) hole-transport-layers (HTLs) in non-fullerene acceptor-based OALCs to achieve record power conversion efficiency (PCE) exceeding 33 % under a light-emitting diode lamp (19500 lx; light intensity IL = 4.5 mW/cm2). The material most widely used for HTLs is poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). OALCs with ALD-processed V2O5 HTLs substantially outperform those with PEDOT:PSS HTLs because they have superior hole selectivity, excellent electron-blocking, a smaller interfacial area, and substantially enhanced step coverage which significantly suppresses charge recombination. Moreover, the proposed V2O5-based OALCs have diffusion-free characteristics into the photoactive region and demonstrate excellent performance stability, maintaining a PCE of 92 % after 1000 h under ambient conditions. The results provide insights that enable simultaneous improvements in the efficiency and ambient stability of OALCs for low-powered IoT applications.

Ti3C2Tx-Modified PEDOT:PSS Hole-Transport Layer for Inverted Perovskite Solar Cells.

PSS is a commonly used hole-transport layer (HTL) in inverted perovskite solar cells (PSCs) due to its compatibility with low-temperature solution processing. However, it possesses lower conductivity than other conductive polymers and metal oxides, along with surface defects, limiting its photovoltaic performance. In this study, we introduced two-dimensional Ti3C2Tx (MXene) as an additive in the PEDOT:PSS HTL with varying doping concentrations (i.e., 0, 0.03, 0.05, and 0.1 wt.%) to tune the electrical conductivity of PEDOT:PSS and to modify the properties of the perovskite film atop it. We noted that the grain size of the CH3NH3PbI3 (MAPI3) perovskite layer grown over an optimal concentration of MXene (0.03 wt.%)-doped PEDOT:PSS increased from 250 nm to 400 nm, reducing charge recombination due to fewer grain boundaries. Ultraviolet photoelectron spectroscopy (UPS) revealed increased work function (WF) from 4.43 eV to 4.99 eV with 0.03 wt.% MXene doping, making the extraction of holes easier due to a more favorable energy level alignment with the perovskite. Quantum chemical investigations based on density functional theory (DFT) were conducted at the ωB97XD/6-311++G(d,p) level of theory to provide more insight into the stability, bonding nature, and optoelectronic properties of the PEDOT:PSS-MXene system. The theoretical investigations revealed that the doping of PEDOT:PSS with Ti3C2Tx could cause a significant effect on the electronic properties of the HTL, as experimentally demonstrated by an increase in the electrical conductivity. Finally, the inverted PSCs employing 0.03 wt.% MXene-doped PEDOT:PSS showed an average power conversion efficiency (PCE) of 15.1%, up from 12.5% for a reference PSC employing a pristine PEDOT:PSS HTL. The champion device with a 0.03 wt.% MXene-PEDOT:PSS HTL achieved 15.5% PCE.

Self-assembled monolayers featuring multi-chlorinated carbazole unit for improving hole extraction efficiency in organic photoelectronic device

Typical PEDOT: PSS hole-transporting layer always suffer from the unmatched energy level, harsher acidity and severe hydroscopicity, which further inducing the severe degradation of device performance and long-term stability simultaneously. Herein, we explore a novel carbazole derived molecule 4Cl-PACz as self-assembled monolayers anchoring directly onto the indium tin oxide (ITO) substrate. The 4Cl-PACz not only exhibits superior optical transmittance than PEDOT: PSS in visible and near-infrared region, but also could upgrade the work function, thus leading to more matched energy level alignment with donor materials to facilitate the hole extraction. Furthermore, 4Cl-PACz is proven to efficiently modify the surface morphology of ITO electrode while simultaneously optimizing the phase-separation of the active layer spin-coated atop. Consequently, devices based on ITO/4Cl-PACz system output a power conversion efficiency (PCE) of 16.8 % based on PM6:Y6 system. The improved performance is mainly attributed to the improvement of energy level alignment and surface morphology, thus leading to improved charge extraction, lower trap-assisted recombination and longer carrier lifetime. Encouragingly, a higher PCE of 18.2 % can be realized when PM6:L8-BO was employed as active layer. Moreover, the optimized OLED based on 4Cl-PACz also presents improved carrier transport, with enhanced luminance and efficiency values than PEDOT: PSS derived ones. This work manifests the advantage of the proposed 4Cl-PACz material for realizing high-performance and stable OSCs and OLEDs.

Modification of PEDOT: PSS to enhance device efficiency and stability of the Quasi-2D perovskite light-emitting diodes

Poly(3,4-ethylenedioxy thiophene): poly(styrene sulfonate) (PEDOT: PSS) is a hole transport layer (HTL) that is often employed in a diverse array of optoelectronic devices, such as perovskite solar cells and perovskite light-emitting diodes (PeLEDs). By simply doping lithium fluoride (LiF) into PEDOT: PSS, we demonstrate that the electrical characteristics of the HTL can be modified. Especially in quasi-2D perovskite LEDs, the crystallization process is regulated by LiF modification, leading to reduced phase impurity defects and improved carrier transport in the perovskite emission layer. Therefore, the luminance and efficiency of the quasi-2D PeLEDs are notably enhanced. The optimized PeLED with LiF modification exhibits a peak luminance of 21517 cd m −2 with 317% higher than the standard PeLED; and a high current efficiency of 39.8 cd A −1 with 237% higher than the standard PeLED. Moreover, the device stability is also improved with a nearly doubled half lifetime due to the reduced phase impurities. The work demonstrates a facile yet effective method for altering PEDOT: PSS hole transport layer, emphasizing the critical role of the underneath layer in the crystallization of quasi-2D perovskites. PEDOT: PSS with LiF modification can notably improve the device efficiency and stability of quasi-two-dimensional perovskite light-emitting diodes. • Electronic properties of the hole transport layer can be modified by lithium fluoride doping. • Reduced phase impurity defects and improved carrier transport. • Device stability is also improved with a nearly doubled half lifetime.

Room-temperature deposited fluorine-doped tantalum pentoxide for stable organic solar cells

Earth-abundant transition metal oxides deposited at room temperature with low-cost methods suitable for large area manufacturing can offer advances in many fields of energy related devices. Here we report the room-temperature deposition of a fluorine-doped tantalum pentoxide using a home-made, low-cost hot-wire deposition system. This novel tantalum oxyfluoride material is super hydrophobic, ultra-transparent within the visible spectrum, and possesses adequate conductivity and suitable valence band and conduction band extrema for acting as efficient hole extraction and electron blocking layer in organic solar cells with the forward architecture. By inserting this material in the form of nanoparticles deposited on top of the commonly used as hole transport layer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, higher efficiencies compared to the reference cells without the nanoparticles were demonstrated in solar cells based on blends of polymer donors with either a fullerene (where maximum achieved efficiency was improved from 6.07% to 7.90%) or a non-fullerene acceptor (reaching values of 13.48% compared to 11.32% of the reference cell). Moreover, significant improvement in device stability was achievd in unencapsulated devices continuously exposed in a humid environment for 500 h. This work demonstrates the unambiguous potential of well-designed metal oxide materials as charge transport and blocking interlayers and protective buffers in organic solar cells and beyond. Home-grown fluorine-doped tantalum pentoxide nanoparticles deposited on top of PEDOT:PSS hole transport layer results in around 19% improved power conversion efficiency and an improved stability in organic solar cells. • Room-temperature deposition of fluorine-doped tantalum pentoxide. • Improved hole extraction and electron blocking properties. • Ta 2 O 5 :F - an inorganic protective buffer layer. • A 19% improved efficiency in organic solar cells. • Improved stability of fullerene and non-fullerene acceptor.

Phosphorus and Selenium Co‐Doped WO3 Nanoparticles for Interface Modification and Photovoltaic Properties Enhancement of Monolayer Planar Silicon/PEDOT:PSS Hybrid Solar Cells

AbstractOrganic/silicon hybrid solar cells have attracted extensive attention owing to their low cost and simple manufacturing process. However, theoretical simulations indicate that the efficiency of organic/silicon hybrid solar cells should exceed 20%. This study demonstrates phosphorus and selenium co‐doped WO3 nanoparticles used for heterojunction solar cell (HSC) modification and theoretically elaborates the effects of these doping elements. The doped WO3 nanoparticles are added into poly(3,4‐ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) films to optimize the physical properties and qualities of the organic layer. The admixture of P/Se‐WOx greatly improves the open‐circuit voltage and fill factor of Si/PEDOT:PSS solar cell devices. In the hole transport layer (HTL)‐based device, the P/Se‐WOx hybrid PEDOT:PSS HTL yields a power conversion efficiency up to 13.64%, which is substantially higher than those of previously reported undoped and doped devices. The generated W5+ in optimized WO3 further indicates that the VI B group elements, such as W or Mo with 5+ state ions, positively influence the HSC performance and would greatly benefit the photovoltaic industry.

Development of MXene / WO 3 embedded PEDOT : PSS hole transport layers for highly efficient perovskite solar cells and X‐ray detectors

A simple solution process was employed to decorate WO3 nanoparticles on 2D conductive Ti3C2TX MXene sheets to arrange the MXene/WO3 hybrid structure. The prepared hybrid composites were established by the Raman scattering, X-ray diffraction, and microscopy studies evidently. The designed hybrid structure, for the first time, was engaged with PEDOT:PSS to alter the hole transport layer (HTL) of perovskite hybrid module for the highly efficient planar solar cell and X-ray detector. The derived outcomes revealed a high power conversion efficiency of 12.26 ± 0.12% for the constructed perovskite solar cell with MXene/WO3/PEDOT:PSS HTL. Similarly, the fabricated X-ray photodetector with MXene/WO3 blended HTL device attained a superior sensitivity of 3.67 ± 0.03 mA Gy−1·cm−2. The results envisaged that HTL/perovskite interface was effectively tuned by the MXene/WO3 heterostructure through their active interface for transfer/collection of charges and appropriately altered energy band alignment, which gave the nod for easy to charge extraction and shortest charge carrier lifetime.

Optimization of the carrier recombination and transmission properties in perovskite LEDs by doping poly (4-vinylpyridine) and graphene quantum dots made of chitin

Light emission intensity and a lifetime of perovskite light-emitting diodes (PeLEDs) have improved considerably through fine-tuning the regulation of carriers’ recombination and transport. This study found that adding poly (4-vinylpyridine) within a CsxPbBry system leads to a dipole–dipole interaction of pyridine-N and Pb2+. This interaction increases the solubility of the CsxPbBry precursor solution, which stabilizes the CsxPbBry crystal structure and induces a CsPbBr3 unitary state. The interaction further generates a polaron region and causes the orderly distribution of excess carriers in the electric field, thus preventing disordered surface charges from structurally damaging the crystal. The PEDOT:PSS hole transport layer mixed with a graphene quantum dot made of chitin tunes the highest occupied molecular orbital to improve carrier transmission efficiency. We fabricated PeLEDs with a peak luminance of 20420 cd m−2 and a fatigue half-life four times higher than original PeLEDs. This stable performance of the device can hasten the commercial development of PeLEDs.

Improving the electrical performance of inverted perovskite solar cell with LiF anode buffer layer

Although the electrical performance of inverted PSCs is a bit lower than that of conventional PSCs at present, it has attracted increasing research attention thanks to its simple architecture for low preparation temperature and negligible hysteresis, and subsequently a high opportunity for industrial application. In general, PEDOT:PSS is employed to serve as hole transport layer (HTL) in inverted PSCs due to its high conductivity, high light transmittance, and aqueous dispersion. However, the mismatch of energy level between PEDOT:PSS and ITO is detrimental to extract the photo-induced holes, hampering further enhancement of the electrical performance of inverted PSCs. Here, a LiF anode buffer layer, whose optimization thickness is 7 nm, has been employed to modify the PEDOT:PSS HTL in inverted PSCs. Thanks to the LiF anode buffer layer, a dramatically enhancement of PCE from 16.01% of reference sample with pristine PEDOT:PSS to 18.18% of PSCs with LiF/PEDOT: PSS HTL. This enhancement is mainly ascribed to improve the charge extraction ability due to the diople effect of LiF. Therefore, this work provides a simple and effective method to increase the electrical performance of inverted PSCs. • A LiF anode buffer layer is employed to modify the PEDOT: PSS in inverted PSCs. • The PCE is a dramatically enhancement from 16.01% with pristine PEDOT:PSS to 18.18% with LiF/PEDOT:PSS. • This work provides a simple and effective method to increase the electrical performance of inverted PSCs.

Comparative study of electrochemically-grown vanadium pentoxide nanostructures synthesized using differential pulse voltammetry, cyclic voltammetry, and chronoamperometry methods as the hole transport layer

Vanadium pentoxide (V2O5) nanostructures were grown on the ITO-coated glass slides using differential pulse voltammetry (DPV), cyclic voltammetry (CV), chronoamperometry (CA) methods, and utilized as the hole transport layer (HTL) in the construction of bulk heterojunction polymer solar cells (BHJ PSCs). The influences of the deposition time in the mentioned methods were investigated to find the best conditions to achieve the highest electrochemical performance from the deposited layer. The morphology of the electrodeposited nanostructures differed by changing the applied potential regime, and V2O5 nanorods (NRDs) were formed by the CV while V2O5 nanoparticles (NPs) formed using DPV and chronoamperometry. Simple adjustment of the applied potential regime and deposition time led to considerable structural and electrochemical changes of the resulting V2O5. Features of the electrochemically-grown V2O5 were compared with each other and with those of the V2O5 prepared using the hydrothermal method. The best sample in each series was selected in terms of suitable surface conductivity, high optical transparency and appropriate energy levels and applied as HTL in BHJ PSCs. Results revealed that the V2O5 sample prepared using DPV provided considerably better electrical, optical and electrochemical features. PSCs prepared based on this sample exhibited a higher power conversion efficiency (PCE) (~ 48%) and fill factor (~2%) than PSCs prepared based on V2O5 synthesized by the hydrothermal method. This was attributed to the high electroactive surface area (0.26±0.003 cm2), high charge mobility (2.44 × 10-4 cm2. V-1s-1) and excellent conductivity (0.03 mS.cm-1) of V2O5 NPs grown using DPV. The best cell provided an open circuit voltage of about 0.56 V, a short circuit current of 9.42 mA cm2, a fill factor of 65.3% and a power conversion efficiency of 3.40%. PCE of this cell was about 60% higher than that considered for the reference device prepared base on the PEDOT:PSS HTL.

Improved Performance of Perovskite Solar Cells by Suppressing the Energy-Level Shift of the PEDOT:PSS Hole Transport Layer

In inverted architectures of perovskite solar cells (PSCs), poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been widely used as the hole transport layer (HTL). An issue occurring in such PSCs is that the hole transport level of PEDOT:PSS shifts upward since methylammonium iodide (MAI) used for the perovskite structure organization interacts with the underlying PEDOT:PSS HTL as a reducing agent, which impedes hole extraction and therefore lowers the performance of PSCs. To overcome this issue, we demonstrate a way of adding tetraethoxysilane (TEOS) into a water-based PEDOT:PSS solution. The HTL spin-coated from the solution contains PEDOT:PSS, which is blended with siloxanes because the polymerization of TEOS takes place via the hydrolysis reaction. This siloxane blending suppresses the MAI-induced reducing reaction and upward energy-level shift of PEDOT:PSS. Using the siloxane-blended PEDOT:PSS HTL in PSCs leads a ∼1.3-fold increase in power conversion efficiencies of iodide-based PSCs from the original ∼10.58% to ∼13.65%.

Flexible CH3NH3PbI3 perovskite solar cells with high stability based on all inkjet printing

At present, there are many reports on the preparation of large area perovskite solar cells based on ink-jet printing. These works mainly focus on the ink-jet printing electrode and perovskite films. The hole transport layer, electron transport layer and other modified layers in the cell structure are still completed by spin coating or coating. We have successfully realized large area CH3NH3PbI3 perovskite solar cells based on all inkjet printing, including PEN/Ag NWS bottom electrode, Ag NWS top electrode, PEDOT:PSS hole transport layer, etc. It was showed that PC71BM Electron transport layer, PEI modified layer and CH3NH3PbI3 perovskite film with high density and good uniformity can be obtained. We have fabricated CH3NH3PbI3 perovskite solar cells with area of 120 cm2, 150 cm2 and 180 cm2 respectively. The results show that the power conversion efficiency of the perovskite solar cell with effective area of 120 cm2 is as high as 16.78% (VOC = 1.02 V, JSC = 21.96 mA/cm2, FF = 75%; 150 cm2: 12.56%, 180 cm2: 10.68%), which is the highest efficiency reported so far. In addition, when the device is placed in the air for six months without packaging, the photoelectric conversion efficiency is reduced to 90% of the initial value. However, the photoelectric conversion efficiency of CH3NH3PbI3 perovskite solar cells with Fluorinated thermoplastic polyurethane film (FTPU) package is only reduced by 5%, which shows excellent device stability.

A pH‐Neutral Polyelectrolyte Hole Transport Layer for Improved Energy Band Structure at the Anode/PTB7 Junction and Improved Solar Cell Performance

In organic solar cells (OSCs), interfacial properties between the donor phase and hole transport layers (HTLs) are critical factors which govern charge extraction efficiency. Many ionic and polar materials are known to function as effective interfacial layers; however, an understanding of how ionic moieties affect the electronic band structure and characteristics of OSCs is lacking. Herein, a new, pH‐neutral polyelectrolyte is introduced that resolves several problems which are encountered with the commonly used HTL, poly(3,4‐ethylenedioxythiopene):polystyrenesulfonate (PEDOT:PSS). An effective p‐type polyelectrolyte dopant is designed, comprising an anionically charged PSS backbone with easily reduced Cu2+ counterions (Cu:PSS), and interfacial properties for HTL/donor interfaces by photoelectron spectroscopy are analyzed. The effects of the polyelectrolyte on interfacial energy levels and charge extraction efficiency between the active layer and HTL are quantified. Using optimized processing conditions, the efficiency can be improved from 8.31% to 9.28% in conventional OSCs compared with a standard PEDOT:PSS HTL. The energy‐level alignment at the HTLs/donor interface determined by UV photoelectron spectroscopy measurements reveals the origin of distinct differences in device performances. The reduced ionization potential (IP) and hole injections barrier (Φh) at the HTL/donor interface play a crucial role in efficient charge extraction in conventional OSCs.

Characteristics of Mo2C-CNTs hybrid blended hole transport layer in the perovskite solar cells and X-ray detectors

Transition metal carbide (Mo2C) and carbon nanotubes (CNTs) have been used to modify the hole transport layers (HTLs) in perovskite solar cells (PSCs) and photodetectors due to their high metallic conductivity, superior charge extraction probability, tunable work function, and high reliability. Here, for the first time, Mo2C, CNTs, and a Mo2C-CNT hybrid were blended with a PEDOT:PSS HTL in an ITO/HTL/CH3NH3PbI3/PCBM/LiF/Al device architecture. The power conversion efficiency of the resulting PSC improved to 11.98% with the use of Mo2C-CNT@PEDOT:PSS HTL compared to the pure PEDOT:PSS (9.17%), Mo2C@PEDOT:PSS (9.82%) and CNT@PEDOT:PSS (10.61%) HTLs. The PSC performance of device prototypes with different loadings (1, 1.5, and 2 wt%) of the Mo2C@CNT nanocomposite in the HTL was also examined. The prepared Mo2C-CNT@PEDOT:PSS HTL-based device was then employed as X-ray photodetector, achieving a maximum sensitivity of 3.56 mA/Gy·cm2. Our findings illustrate the potential for the use of MXene-CNT nanocomposites with a perovskite layer to enhance the efficacy of solar cells and photodetectors.

Inverted Polymer Solar Cells with Annealing-Free Solution-Processable NiO.

Nickel oxide (NiO) offers intrinsic p-type behavior and high thermal and chemical stability, making it promising as a hole transport layer (HTL) material in inverted organic solar cells. However, its use in this application has been rare because of a wettability problem caused by use of water as base solvent and high-temperature annealing requirements. In the present work, an annealing-free solution-processable method for NiO deposition is developed and applied in both conventional and inverted non-fullerene polymer solar cells. To overcome the wettability problem, the typical DI water solvent is replaced with a mixed solvent of DI water and isopropyl alcohol with a small amount of 2-butanol additive. This allows a NiO nanoparticle suspension (s-NiO) to be deposited on a hydrophobic active layer surface. An inverted non-fullerene solar cell based on a blend of p-type polymer PTB7-Th and non-fullerene acceptor IEICO-4F exhibits the high efficiency of 11.23% with an s-NiO HTL, comparable to the efficiency of an inverted solar cell with a MoOx HTL deposited by thermal evaporation. Conventionally structured devices including this s-NiO layer show efficiency comparable to that of a conventional device with a PEDOT:PSS HTL.

Improvement of fill factor by the utilization of Zn-doped PEDOT:PSS hole-transport layers for p-i-n planar type of perovskite solar cells

Poly (3,4-ethylenedioxythiophene)-poly (styrene sulfonate (PEDOT:PSS) is a widely-known conductive polymer mixture that is mostly engaged as a hole transport layer (HTL) in organic and perovskite solar cells (PSCs). In this study, it has been demonstrated that the use of Zn as an additive in PEDOT:PSS solution improved the photovoltaic performance of the ambient air solution-based fabrication of methylammonium lead tri-iodide (MAPbI3) based devices. The short circuit current density (JSC) of the device increased from 15.4 to 17.2 mA/cm2, while the fill factor (FF) improved from 0.70 to 0.83 by using Zn-doped PEDOT:PSS as a hole transport layer (HTL), which is a record value for only γ-butyrolactone (GBL) based MAPbI3 PSCs. Additionally, open-circuit (VOC) value is boosted up from 890 to 925 mV by Zn-doping, which might be linked to the increased work function of the investigated HTLs. Moreover, the synergetic effect of improved electrical conductivity and hole mobility of PEDOT:PSS film and decreased the trap density of perovskite led to an increase of 37% in power conversion efficiency (PCE) and the stability of the inverted planar PSCs.

A Hybrid Hole Transport Layer for Perovskite-Based Solar Cells

This paper presents the effect of a composite poly(3,4-ethylenedioxythiophene) polystyrene sulfonate PEDOT:PSS and copper-doped nickel oxide (Cu:NiOx) hole transport layer (HTL) on the performance of perovskite solar cells (PSCs). Thin films of Cu:NiOx were spin-coated onto fluorine-doped tin oxide (FTO) glass substrates using a blend of nickel acetate tetrahydrate, 2-methoxyethanol and monoethanolamine (MEA) and copper acetate monohydrate. The prepared solution was stirred at 65 °C for 4 h and spin-coated onto the FTO substrates at 3000 rpm for 30 s in a nitrogen glovebox. The Cu:NiOx/FTO/glass structure was then annealed in air at 400 °C for 30 min. A mixture of PEDOT:PSS and isopropyl alcohol (IPA) (in 1:0.05 wt%) was spun onto the Cu:NiOx/FTO/glass substrate at 4000 rpm for 60 s. The multilayer structure was annealed at 130 °C for 15 min. Subsequently, the perovskite precursor (0.95 M) of methylammonium iodide (MAI) to lead acetate trihydrate (Pb(OAc)2·3H2O) was spin-coated at 4000 rpm for 200 s and thermally annealed at 80 °C for 12 min. The inverted planar perovskite solar cells were then fabricated by the deposition of a photoactive layer (CH3NH3PbI3), [6,6]-phenyl C61-butyric acid methyl ester (PCBM), and a Ag electrode. The mechanical behavior of the device during the fabrication of the Cu:NiOx HTL was modeled with finite element simulations using Abaqus/Complete Abaqus Environment CAE. The results show that incorporating Cu:NiOx into the PSC device improves its density–voltage (J–V) behavior, giving an enhanced photoconversion efficiency (PCE) of ~12.8% from ~9.8% and ~11.5% when PEDOT:PSS-only and Cu:NiOx-only are fabricated, respectively. The short circuit current density Jsc for the 0.1 M Cu:NiOx and 0.2 M Cu:NiOx-based devices increased by 18% and 9%, respectively, due to the increase in the electrical conductivity of the Cu:NiOx which provides room for more charges to be extracted out of the absorber layer. The increases in the PCEs were due to the copper-doped nickel oxide blend with the PEDOT:PSS which enhanced the exciton density and charge transport efficiency leading to higher electrical conductivity. The results indicate that the devices with the copper-doped nickel oxide hole transport layer (HTL) are slower to degrade compared with the PEDOT:PSS-only-based HTL. The finite element analyses show that the Cu:NiOx layer would not extensively deform the device, leading to improved stability and enhanced performance. The implications of the results are discussed for the design of low-temperature solution-processed PSCs with copper-doped nickel oxide composite HTLs.