Perovskite Tandem Solar Cells Research Articles

Filtered spectrum modeling of high-performance perovskite tandem solar cells: Tailoring absorber properties and electron/hole transport layers for 31.55 % efficiency

In this study, the perovskite tandem solar cell (TPSC) has been accomplished using SCAPS-1D. The present study focuses on comprehensive exploration and detailed optimization using various strategies constructing a tandem device. To calculate high photovoltaic power conversion efficiency (PCE), the numerical analysis has been carried out for a wide-bandgap halide (WBH) FA0.75Cs0·25Pb(I0·8Br0.2)3 of bandgap 1.67eV and a Pb–Sn based narrow-bandgap halide (NBH) FA0.7MA0.3Pb0·5Sn0·5I3 of bandgap 1.22eV as absorber layer in top-cell (TCELL) and bottom-cell (BCELL) respectively. The WBH has huge potential as a front light absorber and the NBH based BCELL provides stability and high performance by accepting high and low energy photons respectively. This method mitigates thermalization and non-absorbed photon loss which results in the growth in PCE. The proposed work demonstrates the impact of active-layer thickness along with defect density on the solar-cell parameters. It has been observed that defect density is low for the optimal performance. An investigation for various electron transport medium (ETMs) and hole transport medium (HTMs) has been done to secure an optimum performing TCELL as well as BCELL. Using filtered-spectrum study along with current-matching method, every PV metric parameter has been analyzed after their deployment into tandem configuration. The numerical investigation has shown promising photovoltaic parameters with aa high open circuit voltage (VOC) of 2.33 V, a short circuit current density (JSC) of 17.07 mA/cm2, a fill factor (FF) of 79.34 % and PCE of 31.55 % in tandem configuration.

High‐Throughput Indirect Gravure Printing Applied to Low‐Temperature Metallization of Silicon‐Based High‐Efficiency Solar Cells

Herein, this work is dedicated to a both exotic and promising printing technique in silicon (Si) photovoltaics (PV). Indirect gravure printing is investigated as a metallization technique focusing on low‐temperature applications, such as Si heterojunction (SHJ) and perovskite Si tandem solar cells. One advantage of this rotary printing technique is that its components are very durable. From graphical industry, it is known that gravure cylinders show almost no wearing during multiple printing. Additionally, rotary printing techniques offer great throughput. Therefore, indirect gravure printing can reduce costs significantly in PV production. In this work, short process cycle times of 0.9 s cell−1 for industrial wafers (edge length of 156.75 mm) are demonstrated. Using an appropriate production platform even enables cycle times of down to 0.5 s cell−1. Busbarless SHJ half cells with non‐optimized gravure‐printed front grids reach a mean photoconversion efficiency that is (1.7 ± 0.5) %abs lower compared to screen‐printed reference samples, however, cycle time is reduced. The metal contacts exhibit a mean shading width of (65 ± 16) μm and an average height of (5 ± 1) μm. Applied to SHJ solar cells’ rear, such metallization can replace screen‐printed contacts with 0.1%abs efficiency loss only, as device simulations reveal.

Ionic‐Rich Vermiculite Tailoring Dynamic Bottom‐Up Gradient for High‐Efficiency Perovskite Solar Cells

AbstractMixed‐halide perovskites are emerging as excellent photovoltaic candidates because of their tunable bandgaps for semitransparent and tandem perovskite solar cells. However, the notorious film quality originated from the rapidly downward crystallization process susceptibly propagates enormous detrimental defects, which deteriorate the photovoltaic performance and accelerate halide segregation. To address this issue, herein, a multilayer alkalis‐intercalated‐vermiculite is employed as pre‐buried interface modifier to regulate the perovskite lattice property. The matchable lattice structure between perovskite and vermiculite by forming Pb─O bond not only releases the interfacial strain during the film growth but also the embedded alkalis ions can gradually diffuse into perovskite lattice to form a favorable vertical gradient owing to the weak interlamellar van der Waals interaction, playing bis‐roles of atomical lubricant and ion‐reservoir to eliminate detrimental defects. As a result, the film quality and lattice stability is significantly improved with suppressed phase segregation for mixed‐halide perovskites, accompanying a champion efficiency of 11.42% for carbon‐based CsPbIBr2 device, 15.25% for carbon‐based CsPbI2Br device and 23.17% for p‐i‐n inverted (Cs0.05MA0.05FA0.9)Pb(I0.93Br0.07)3 cell. This work provides a new strategy on buried interface engineering for making high‐efficiency and stable perovskite platforms.

Double Perovskite Tandem Solar Cells: Design and Performance Investigation of the Use of CABB and CCSC as Top and Bottom Cell Absorber Materials

Double Perovskite Tandem Solar Cells: Design and Performance Investigation of the Use of CABB and CCSC as Top and Bottom Cell Absorber Materials

Interface Reactive Sputtering of Transparent Electrode for High-Performance Monolithic and Stacked Perovskite Tandem Solar Cells.

Sputtered indium tin oxide (ITO) fulfills the requirements of the top transparent electrodes (TTEs) in semitransparent perovskite solar cells (PSCs) and stacked tandem solar cells (TSCs) as well as the recombination layers in monolithic TSCs. However, the high-energy ITO particles will cause damage to the devices and reduce the photovoltaic performance. Herein, the interface reactive sputtering strategy has been proposed and implemented to construct cost-effective TTEs with high transmittance and excellent carrier transporting ability, aiming to realize high-performance semitransparent and tandem PSCs. Polyethylenimine (PEI) was chosen as the interface reactant, of which abundant amino groups on PEI can react with sputtered ITO nanoparticles so that coordination compounds can be formed during the ITO deposition process, facilitating the carrier transport at the interface of C60/PEI/ITO. Besides, the impact force of energetic ITO particles is greatly alleviated, and the intactness of the underlying C60 layer and perovskite layer is guaranteed. Thus, the prepared semitransparent subcells achieve a significantly enhanced power conversion efficiency (PCE) of 19.17%, surpassing those based on C60/ITO (11.64%). Moreover, the PEI-based devices demonstrate excellent storage stability, which maintains 98% of their original PCEs after 2000 hours. On the strength of the interface reactive sputtering ITO electrode, we successfully fabricated a stacked all-perovskite TSC with a PCE of 26.89% and a monolithic perovskite-organic TSC with a PCE of 24.33%. This work has provided a facile and instrumental solution for rendering TTEs function well in semitransparent and tandem PSCs. This article is protected by copyright. All rights reserved.

Design of Efficient Inverted NiOX‐Based Three‐Terminal Back‐Contact All Perovskite Tandem Solar Cells

AbstractThe development of efficient all perovskite tandem solar cells has faced challenges related to current matching and optical losses. In this work, a design of a non‐coplanar three‐terminal (3T) all perovskite tandem solar cell is presented, which consists of a p‐i‐n inverted NiOX‐based CsPbI2Br perovskite top cell, and a FA0.6MA0.4Sn0.5Pb0.5I3 perovskite bottom cell with back‐contact (BC) device structure. It effectively mitigated the optical losses introduced in non‐absorbing layers and resulted in a 2.9% absolute efficiency improvement compared to that of planar sandwich‐type 3T tandems. Both optical and electrical characteristics of the multi‐terminal tandem cells are investigated. Then, it is focused on understanding the impact of top cell thickness on overall non‐coplanar BC 3T‐tandem performance, considering low‐energy photon optical reflection and carrier transport distance. Following optimizations of energy level and device structure, an efficiency of 32.16% is achieved, with non‐coplanar BC 3T device architecture: top cell consisting of hole extraction layer (ITO/NiOx), CsPbI2Br absorber layer, and electron extraction layer (ZnO/FA0.6MA0.4Sn0.5Pb0.5I3/SnO2/Ag); and bottom cell (Ni/NiOx/FA0.6MA0.4Sn0.5Pb0.5I3/SnO2/Ag); bottom perovskite layer has two functions, one is electron transport layer for top cell, and the other is low‐energy photon absorption layer in bottom cell. It provides insight and a promising pathway for manufacturing high‐efficient all perovskite tandem solar cells.

Intermediate Phase Suppression with Long Chain Diammonium Alkane for High Performance Wide-Bandgap and Tandem Perovskite Solar Cells.

Wide bandgap (WBG) perovskite can construct tandem cells with narrow bandgap solar cells by adjusting the band gap to overcome the Shockley-Queisser limitation of single junction perovskite solar cells (PSCs). However, WBG perovskites still suffer from severe nonradiative carrier recombination and large open-circuit voltage loss. Here, this work uses an in situ photoluminescence (PL) measurement to monitor the intermediate phase evolution and crystallization process via blade coating. This work reports a strategy to fabricate efficient and stable WBG perovskite solar cells through doping a long carbon chain molecule octane-1,8-diamine dihydroiodide (ODADI). It is found that ODADI doping not only suppresses intermediate phases but also promote the crystallization of perovskite and passivate defects in blade coated 1.67eV WBG FA0.7 Cs0.25 MA0.05 Pb(I0.8 Br0.2 )3 perovskite films. As a result, the champion single junction inverted PSCs deliver the efficiencies of 22.06% and 19.63% for the active area of 0.07 and 1.02 cm2 , respectively, which are the highest power conversion efficiencies (PCEs) in WBG PSCs by blade coating. The unencapsulated device demonstrates excellent stability in air, which maintains its initial efficiency at the maximum power points under constant AM 1.5G illumination in open air for nearly 500h. The resulting semitransparent WBG device delivers a high PCE of 20.06%, and the 4-terminal all-perovskite tandem device delivers a PCE of 28.35%.

Reducing Hole Trap Density in Sn–Pb Perovskite Solar Cells via Molecular Phenylhydrazine

Narrow‐bandgap Sn–Pb‐alloyed perovskite is potential for a bottom cell in perovskite tandem solar cells. However, Sn‐contained perovskites tend to be readily oxidized in air atmosphere, which has ill influence on stability and photovoltaic performance. Herein, a method to suppress oxidation of divalent tin via post‐treatment of perovskite film with phenylhydrazine is reported. Phenylhydrazine‐treated FA0.5MA0.5Pb0.5Sn0.5I3 perovskite films effectively reduce the hole traps caused by the oxidation of Sn2+ on the perovskite surfaces. In addition, surface energetics are well aligned by post‐treatment, which is beneficial for voltage gain and charge transport. As a result, power conversion efficiency (PCE) is increased from 18.16% to 20.67% after post‐treatment due mainly to the significant improvement of open‐circuit voltage from 0.75 to 0.83 V. Furthermore, the device stability is improved, where 91.67% of initial PCE is maintained after 1000 h.

On Numerical Modelling and an Experimental Approach to Heterojunction Tandem Solar Cells Based on Si and Cu2O/ZnO—Results and Perspectives

A comparative analysis of three advanced architectures for tandem solar cells (SCs) is discussed, respectively: metal oxide, thin film, and perovskite. Plasmonic solar cells could further increase solar cell efficiency. Using this development, an innovative PV technology (an SHTSC based on metal oxides) represented by a four-terminal Cu2O/c-Si tandem heterojunction solar cell is investigated. The experimental and numerical modelling study defines the main aim of this paper. The experimental approach to SHTSCs is analysed: (1) a Cu2O layer is deposited using a magnetron sputtering system; (2) the morphological and optical characterization of Cu2O thin films is studied. The electrical modelling of silicon heterojunction tandem solar cells (SHTSCs) is discussed based on five simulation tools for the optimized performance evaluation of solar devices. The main novelty of this paper is represented by the following results: (1) the analysis suggests that the incorporation of a buffer layer can improve the performance of a tandem heterojunction solar cell; (2) the effect of interface defects on the electrical characteristics of the AZO/Cu2O heterojunction is discussed; (3) the stability of SHTSCs based on metal oxides is studied to highlight the degradation rate in order to define a reliable solar device. Perspectives on SHTSCs based on metal oxides, as well as Si perovskite tandem solar cells with metal oxides as carrier-selective contacts, are commented on.

Design and simulation of three-junction all perovskite tandem solar cells: A path to enhanced photovoltaic performance

Despite numerous publications on two-junction tandems using SCAPS-1D simulation, there is a gap in research regarding three-junction tandems. This paper explores the advantages of three junction all-perovskite tandem solar cells (3J-APTSC) where we introduce a new methodology utilizing two-step filtered spectrum and current matching techniques in SCAPS-1D to design realistic tandem solar cells. Crucial steps involve determining filtered spectrum and current matching points among sub-cells for tandem optimization. Our designed three-terminal tandem solar cell exhibits promising photovoltaic parameters, including VOC: 3.76 V, JSC: 10.70 mA/cm2, FF: 69.00 %, and PCE: 26.24 %, achieved through optimized active layer thicknesses. This thorough examination of 3J-APTSC offers insights that could drive the future development of highly efficient tandem solar cells.

Surface heterojunction based on n-type low-dimensional perovskite film for highly efficient perovskite tandem solar cells.

Enhancing the quality of junctions is crucial for optimizing carrier extraction and suppressing recombination in semiconductor devices. In recent years, metal halide perovskite has emerged as the most promising next-generation material for optoelectronic devices. However, the construction of high-quality perovskite junctions, as well as characterization and understanding of their carrier polarity and density, remains a challenge. In this study, using combined electrical and spectroscopic characterization techniques, we investigate the doping characteristics of perovskite films by remote molecules, which is corroborated by our theoretical simulations indicating Schottky defects consisting of double ions as effective charge dopants. Through a post-treatment process involving a combination of biammonium and monoammonium molecules, we create a surface layer of n-type low-dimensional perovskite. This surface layer forms a heterojunction with the underlying 3D perovskite film, resulting in a favorable doping profile that enhances carrier extraction. The fabricated device exhibits an outstanding open-circuit voltage (VOC) up to 1.34V and achieves a certified efficiency of 19.31% for single-junction wide-bandgap (1.77eV) perovskite solar cells, together with significantly enhanced operational stability, thanks to the improved separation of carriers. Furthermore, we demonstrate the potential of this wide-bandgap device by achieving a certified efficiency of 27.04% and a VOC of 2.12V in a perovskite/perovskite tandem solar cell configuration.

Enhanced efficiency in two-terminal all-perovskite tandem solar cells via binary functional high polymer doping strategy

An enhanced power conversion efficiency (PCE) of 26.1 % has been achieved in two-terminal (2T) all-perovskite tandem perovskite solar cells (TPSCs) via a binary functional high polymer doping strategy. By incorporating methylene diphenyl diisocyanate polyurethane (MDI-PU) and PJ71 into the wide bandgap (WBG) and narrow bandgap (NBG) perovskite layers, respectively, the perovskite crystalline quality of them was significantly improved. The optimized PCE of the WBG top cell and the NBG bottom cell achieved 17.6 % and 20.9 %, respectively. After continuous dark storage of 150 days in nitrogen-filled glovebox, the PCE of optimized TPSC remained 94.2 % of initial. TPSCs on flexible substrates of polyethylene naphthalate (PEN) and silk-derived substrate (SDS) were also studied. With the binary polymer doping strategy, the PEN-based TPSC achieved a champion PCE of 22.2 %, and exhibited excellent anti-bending ability compared with control. The champion SDS-based TPSC achieved the PCE of 11.6 %, and showed enhanced anti-stretching ability. We demonstrate that strong coordinate bonding formed between the O atom in the carbonyl group of MDI-PU and the Pb2+ ions at the grain boundaries (GBs) in WBG perovskite. For the NBG layer, the S atoms in the thiophene structure of PJ71 interact with the Pb2+ and Sn2+ ions in the NBG perovskite and effectively passivate the GB defects. The study suggests the potential for developing new generation multi-functional optoelectronic high polymers to further boost the performance of 2T all-perovskite TPSCs.

Numerical Simulation of Lead-Free Tin and Germanium Based All Perovskite Tandem Solar Cell

The ability to customize the materials bandgaps makes perovskite solar cells a promising candidate for hybrid-tandem applications. This allows them to effectively utilize parts of the solar spectrum that silicon-based solar cells cannot efficiently capture, resulting in higher absorption coefficients. However, there is a lack of research on lead-free all-perovskite tandem solar cells, and secondary data on materials is limited. One of the main challenges in previous studies is the high cost and solid structure of traditional silicon-based solar cells, which require significant storage space. Additionally, lead-based perovskite solar cells pose environmental concerns due to their water solubility and potential harmful effects upon consumption. To address these issues, thin-film perovskite solar cells with liquid solvents are employed in the solar cell design. Lead is replaced with germanium and tin-based perovskites, which exhibit comparable photovoltaic performance to silicon. In the present work, the OghmaNano simulation tool was utilized to conduct numerical simulation of the perovskite design. The perovskite solar cell layers were structured as follows: FTO/ZnO/MAGeI3/Spiro-OMeTAD/FAMASnGeI3/Cu2O/Au. The variables considered included optimum layer thicknesses and bandgaps, as well as the most suitable materials for the ETL and HTL, aiming to obtain the highest efficiency. Based on the simulation results, the proposed perovskite structure shows remarkable photovoltaic parameters. The Voc was measured at 0.84 V Jsc of 16.1 mA/cm2, FF of 0.825, and PCE that reached 11.12%. This project contributes to future research on materials for the ETL and HTL of lead-free, tin and germanium based APTSCs.

Luminescence coupling in 28.4%-efficient tandem solar cell utilizing 20.8%-efficient perovskite minimodule stacked on silicon cell

The total power conversion efficiency (PCE) of 28.4% with an aperture area of 64 cm2 on a four-terminal (4T) tandem solar cell with a 20.8% efficiency-semitransparent perovskite module (SPM) with a series interconnection structure and a conventional passivated emitter and rear cell type crystalline silicon solar cell is independently confirmed. This is the independently confirmed record PCE of a 4T perovskite and crystalline silicon tandem solar cell with a structure having the same active area for both top and bottom cells. The impact of the luminescence coupling monitored by the silicon solar cell in the 4T tandem solar cell was investigated based on electrical properties of the top SPM analyzed by a simple one-diode equivalent circuit model.

Performance assessment of an eco-friendly tandem solar cell based on double perovskite Cs2AgBiBr6

Tandem solar cells have a wider photon absorption range, allowing them to provide better efficiency than single-junction SC. The upper cell absorbs high-energy photons, while the lower cell absorbs low-energy filtered photons. However, in order to obtain affordable, efficient, and long-lasting SC, the absorber layers of the top and bottom cells must be integrated with an adequate bandgap. This research suggests tandem perovskite solar cells as upper band active materials in this setting. The Si homojunction solar cell's performance was improved by investigating the thicknesses of the p−type and n−type layers, doping concentrations, and defect densities. The thickness variation of the perovskite solar cell (100−400nm) is then optimized. To precisely replicate the tandem devices, the estimated spectra of the perovskite SC are optically filtered onto the lower cells. Current matching was achieved by adjusting the thickness of the perovskite sub-cell with different bottom layer thicknesses, and the optimized efficiency of 36.26% for the perovskite/Si tandem device was shown. The discoveries will open the door for the upcoming creation of high−efficiency, low-energy solar cells.

Optical–electrical simulation and optimization of an efficient lead-free 2T all perovskite tandem solar cell

The characteristics of a lead-free all perovskite tandem solar cell (P-TSC) are studied in this study. All P-TSCs were developed with the goal of breaking through the theoretical power conversion efficiency (PCE) limit for single-junction (SJ) perovskite solar cells (PSCs) established by Shockley and Queisser. Solving the toxicity problem in lead-containing sub-cells is essential for the continued growth of all P-TSCs. Here, we first present a coupled three-dimensional (3D) optical–electrical simulation of two lead-free SJ MAGeI3(Eg=1.9eV) and MASnI3(Eg=1.3eV) PSCs. The results showed that the PCE of the SJ-wide bandgap (WBG) and SJ-narrow bandgap (NBG) PSCs is 19.59% and 15.57%, respectively. Next, a two-terminal (2T) eco-friendly all P-TSC with combines these two solar cells has been designed, where the MAGeI3-PSC serves as the top sub-cell and the MASnI3-PSC serves as the bottom sub-cell. By establishing the current matching condition between two sub-cells in the 2T structure, the matched short-circuit current density (Jsc) and PCE are obtained 12.30mA/cm2 and 28.46%, respectively. Herein, a 299 nm-thick NBG-absorber layer and a 200 nm-thick WBG-absorber layer are required. In order to increase the matched Jsc and PCE and decrease the required NBG-absorber layer thickness, the parasitic absorption and reflection losses are minimized by selecting the best materials for the transparent conductive oxide (TCO) front contact and interconnecting (IC) layers, as well as the addition of an anti-reflection (AR) layer at the air/device interface as light management strategies. The results indicate that, under the current matching condition, improving the structure would lead to in a 76 nm reduction in the NBG-absorber layer’s required thickness and a 16.44% increase in PCE. Finally, we suggested the optimized 2T non-Pb all P-TSC with a high PCE of 33.14% that is environmentally safe.

Constructing tin oxides Interfacial Layer with Gradient Compositions for Efficient Perovskite/Silicon Tandem Solar Cells with Efficiency Exceeding 28.

Atomic layer deposition (ALD) growth of conformal thin SnOx films on perovskite absorbers offers a promising method to improve carrier-selective contacts, enable sputter processing, and prevent humidity ingress toward high-performance tandem perovskite solar cells. However, the interaction between perovskite materials and reactive ALD precursor limits the process parameters of ALD-SnOx film and requires an additional fullerene layer. Here, it demonstrates that reducing the water dose to deposit SnOx can reduce the degradation effect upon the perovskite underlayer while increasing the water dose to promote the oxidization can improve the electrical properties. Accordingly, a SnOx buffer layer with a gradient composition structure is designed, in which the compositionally varying are achieved by gradually increasing the oxygen source during the vapor deposition from the bottom to the top layer. In addition, the gradient SnOx structure with favorable energy funnels significantly enhances carrier extraction, further minimizing its dependence on the fullerene layer. Its broad applicability for different perovskite compositions and various textured morphology is demonstrated. Notably, the design boosts the efficiencies of perovskite/silicon tandem cells (1.0cm2 ) on industrially textured Czochralski (CZ) silicon to a certified efficiency of 28.0%.

Numerical analysis of carbon-based perovskite tandem solar cells: Pathways towards high efficiency and stability

Multi-junction solar cells exhibit superior power conversion efficiency (PCE) in comparison with their single-junction counterparts. The tunable bandgap, low-cost, elevated short circuit current density (Jsc), and open-circuit voltage (Voc) of perovskite solar cells (PSCs) have led to their widespread adoption as top sub-cells in tandem devices. Stability remains a significant challenge for these cells. To address this issue, carbon perovskite solar cells (CPSCs) have emerged as a potential solution, offering enhanced stability without hole transport layers (HTLs). This study focuses on the simulation of HTL-free CPSCs using an improved electron transport material (ETM) instead of TiO2. The implementation of this enhancement leads to a notable increase in the PCE of the CPSCs, rising from 7.97 % to 14.38 %. Through optimizing the defect concentration and doping density of the perovskite absorber layer, a significant improvement in the PCE is achieved, reaching 16.87 %. A novel configuration incorporating a gradient doping profile in the perovskite layer is introduced, leading to a remarkable enhancement in the PCE, which reaches 22.22 %. Two absorber materials are suggested, CIGS and GeTe, as bottom sub-cells. Three tandem cell configurations, PSC/CIGS, CPSC/CIGS, and CPSC/GeTe, are rigorously explored based on the optimized sub-cells. The PCEs of the proposed configurations are found to be 30.52 %, 22.7 %, and 36.59 %, respectively. Computational analysis reveals that the PSC/CIGS tandem cell exhibits lower stability against temperature variations compared to CPSC/CIGS and CPSC/GeTe. Additionally, the proposed CPSC/GeTe tandem is highly praised as a favorable contender, offering both high efficiency and stability among the various configurations considered in this study.

Side-chain engineering of benzotriazole-based polymers as hole transport material enables high-efficiency CsPbI2Br single-junction and tandem perovskite solar cells

Rational design and synthesis of high-performance doping-free hole transport polymers is critical to achieve high-efficiency and stable perovskite solar cells (PSCs). Side chain engineering is a widely employed strategy for modulating the photoelectronic properties of polymers. In this study, based on dithieno[2,3-d;2′,3′-d′]benzo[1,2-b;4,5-b′]dithiophenes (DTBDT) as D unit, benzo[d][1,2,3]triazole (BTA) as A segment, and thiophene as a π bridge, three D-π-A type polymeric materials with different length of alkyl side chain (PE51, PE52, and PE53) were utilized as hole transport materials in CsPbI2Br-based PSCs and perovskite/organic tandem solar cells (TSCs). With the increase of alkyl chain length from 2-butyloctyl (PE51) to 2-hexyldecyl (PE52) and to 2-octyldodecyl (PE53), the highest occupied molecular orbital energy level of the polymer gradually decreases, and the molecular stacking of the material gradually shifts from edge-on stacking to face-on stacking. Moreover, among three polymers, the PE53 exhibits the most efficient hole extraction at the CsPbI2Br/hole transport layer (HTL) interface. Hence, the CsPbI2Br-based PSCs and perovskite/organic TSCs employing PE53 as HTL realize the highest power conversion efficiency (PCE) of 17.65% and 23.07%, respectively. Our results indicate that side chain engineering of HTM is an effective strategy to modulate their molecular orientation and improve the photovoltaic performance of PSCs.

Surface-functionalized hole-selective monolayer for high efficiency single-junction wide-bandgap and monolithic tandem perovskite solar cells

Carbazole moiety-based 2PACz ([2-(9H-carbazol-9-yl)ethyl]phosphonic acid) self-assembled monolayers (SAMs) are excellent hole-selective contact (HSC) materials with abilities to excel the charge-transfer-dynamics of perovskite solar cells (PSCs). Herein, we report a facile but powerful method to functionalize the surface of 2PACz-SAM, by which reproducible, highly stable, high-efficiency wide-bandgap PSCs can be obtained. The 2PACz surface treatment with various donor number solvents improves assembly of 2PACz-SAM and leave residual surface-bound solvent molecules on 2PACz-SAM, which increases perovskite grain size, retards halide segregation, and accelerates hole extraction. The surface functionalization achieves a high power conversion efficiency (PCE) of 17.62% for a single-junction wide-bandgap (∼1.77 eV) PSC. We also demonstrate a monolithic all-perovskite tandem solar cell using surface-engineered HSC, showing high PCE of 24.66% with large open-circuit voltage of 2.008 V and high fill-factor of 81.45%. Our results suggest this simple approach can further improve the tandem device, when coupled with a high-performance narrow-bandgap sub-cell.