Reproducible Perovskite Solar Cells Research Articles

The Effect of Interfacial Humidity on the Printing of Highly Reproducible Perovskite Solar Cells in the Air

AbstractMoisture is a double‐edged sword in the nucleation and crystallization of perovskite films. In the presence of appropriate moisture in the air, grain boundaries are expected to merge neighboring grains, promoting the conversion of unreacted ions, resulting in large grains and pinhole‐free films. Adversely, excessive moisture can have detrimental effects on perovskite by damaging its crystalline structure. Controlling humidity precisely and removing excessive moisture from the interface is crucial to the printing of high‐quality and reproducible films in the air, which will undoubtedly promote the rapid commercialization of perovskite solar cells. Here, a method for high‐yield printing of perovskite films is developed using interfacial moisture as a research object. The finite element simulation reveals that interfacial moisture is the key factor affecting the quality of perovskite film formation, regardless of the ambient moisture. The results show that when the interfacial humidity is in the range of 7%–25%, the films exhibit high‐quality crystallization. The devices produced by this method exhibit a yield of 92%, indicating a promising pathway to attain highly reproducible perovskite films with superior optoelectronic properties. The air‐printing process will provide a broad guide to the commercial manufacture of high‐performance perovskite optoelectronic devices.

Bandgap Engineering of Two‐Step Processed Perovskite Top Cells for Perovskite‐Based Tandem Photovoltaics

AbstractFor high‐performance application of perovskite solar cells (PSCs) in monolithic perovskite/silicon tandem configuration, an optimal bandgap and process method of the perovskite top cell is required. While the two‐step method leads to regular perovskite film crystallization, engineering wider bandgaps (Eg > 1.65 eV) for the solution‐based two‐step method remains a challenge. This work introduces an effective and facile strategy to increase the bandgap of two‐step solution‐processed perovskite films by incorporating bromide in both deposition steps, the inorganic precursor deposition (step 1, PbBr2) and the organic precursor deposition (step 2, FABr). This strategy yields improved charge carrier extraction and quasi‐Fermi level splitting with power conversion efficiencies (PCEs) of up to 15.9%. Further improvements are achieved by introducing CsI in the bulk and utilizing LiF as surface passivation, resulting in a stable power output exceeding 18.5% for Eg = 1.68 eV. This additional performance boost arises from enhanced perovskite film crystallization, leading to improved charge carrier extraction. Laboratory scale monolithic perovskite/silicon solar cells (TSCs) (1 cm2 active area) achieve PCEs up to 23.7%. This work marks a significant advancement for wide bandgap two‐step solution‐processed perovskite films, enabling their effective use in high‐performance and reproducible PSCs and perovskite/silicon TSCs.

Wettability Improvement of a Carbazole-Based Hole-Selective Monolayer for Reproducible Perovskite Solar Cells

The wettability issue associated with the Me-4PACz hole-selective monolayer is solved by the introduction of the second component to the precursor solution. This results in a similar performance while simultaneously significantly improving the yield of the devices.

C-N linked donor type porphyrin derivatives: unrevealed hole-transporting materials for efficient hybrid perovskite solar cells.

A new series of Zn(II) and Cu(II)-based porphyrin complexes 5a and 5b doubly functionalised with carbazole units were developed to be used as hole-transporting materials (HTMs) in perovskite solar cells (PSCs). These complexes were obtained via a nucleophilic substitution reaction mediated by PhI(OAc)2/NaAuCl4·2H2O, or using C-N transition metal-assisted coupling. The hole extraction capability of 5a and 5b was assessed using cyclic voltammetry; this study confirmed the better alignment of the Zn(II) complex 5a with the perovskite valence band level, compared to the Cu(II) complex 5b. The optimised geometry and molecular orbitals of both complexes also corroborate the higher potential of 5a as a HTM. Photoluminescence characterisation showed that the presence of 5a and 5b as HTMs on the perovskite surface resulted in the quenching of the emission, matching the hole transfer phenomenon. The photovoltaic performance was evaluated and compared with those of reference cells made with the standard HTM spiro-OMeTAD. The optimised 5-based devices showed improvements in all photovoltaic characteristics; their open circuit voltage (Voc) reached close to 1 V and short-circuit current density (Jsc) values were 13.79 and 9.14 mA cm-2 for 5a and 5b, respectively, disclosing the effect of the metallic centre. A maximum power conversion efficiency (PCE) of 10.01% was attained for 5a, which is 65% of the PCE generated by using the spiro-OMeTAD reference. This study demonstrates that C-N linked donor-type porphyrin derivatives are promising novel HTMs for developing efficient and reproducible PSCs.

Polymer‐Regulated SnO2 Composites Electron Transport Layer for High‐Efficiency n–i–p Perovskite Solar Cells

SnO2 electron transport layer (ETL) plays a critical role in constructing a planar perovskite solar device. Improving SnO2 ETL properties and understanding of interfacial energy loss are key factors to fabricate highly efficient and reproducible perovskite solar cells (PSCs). Herein, a nonionic surfactant, polyethylene oxide‐polypropylene oxide‐polyethylene oxide (P123), is introduced to suppress the aggregation of SnO2 nanoparticles for a uniform SnO2 ETL. The P123 polymer can maintain the SnO2 colloidal size around 10 nm over 72 h at 35 °C and thus promote the dispersion of nanoparticles in SnO2 precursor. By spin coating P123‐doped SnO2 (SnO2‐P) colloid, the compactness and uniformity of SnO2 layer are improved significantly. Correspondingly, SnO2‐P‐based devices demonstrate a champion efficiency with enhanced open‐circuit voltage (V OC) of 1.162 V. Due to the SnO2/perovskite interface binding interaction, the devices gain a high long‐term stability, retaining 85% of their initial performance after 1000 h storage in air. Equally important, the polymer‐regulated ETL allows a competitive efficiency of 17.44% with active area of 1.00 cm2, exhibiting much potential for large‐scale solar devices. This ETL modification approach provides a new and simple route to improve the quality of SnO2 colloid solution for fabricating efficient perovskite devices.

Facile Physical Modifications of Polymer Hole Transporting Layers for Efficient and Reproducible Perovskite Solar Cells with Fill Factor Exceeding 80%

The hole transport materials that interact with the indium tin oxide (ITO) surface can be processed into monomolecular layers (MLs), which often exhibit different surface and electronic properties than their thin‐film counterparts. Herein, it is found that poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine] (PTAA) films (R‐PTAA) can be easily processed into ML (M‐PTAA) due to the van der Waals interaction between ITO and PTAA. However, compared with R‐PTAA, the work function (WF) and conductivity of M‐PTAA are simultaneously reduced by the charge transfer at the ITO/PTAA interface. To address this issue, a modified monomolecular layer strategy (m‐MLS) is developed, where a small amount of 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4TCNQ) is introduced to enhance the interaction force between ITO and PTAA. PTAA treated by m‐MLS (F‐PTAA) has a hydrophilic physical surface, closely matching electronic energy level with the perovskite layer and smaller bulk resistance. As a result, the efficiency and reproducibility of perovskite solar cells (PSCs) are substantially improved. PSCs based on F‐PTAA demonstrated the highest power conversion efficiency (PCE) of 19.7% with a fill factor of over 80%. This study inspires the development of novel interface modification materials, and provides a simple and convenient direction for the fabrication of high‐performance and reproducible inverted PSCs with high fill factors.

Stability Improvement and Performance Reproducibility Enhancement of Perovskite Solar Cells Following (FA/MA/Cs)PbI3–xBrx/(CH3)3SPbI3 Dimensionality Engineering

Mixed halide hybrid perovskites are strong candidates for fabrication of efficient, stable and reproducible perovskite solar cells (PSCs). To restrain intrinsic volatility and ionic migration effec...

Efficient Anti-solvent-free Spin-Coated and Printed Sn-Perovskite Solar Cells with Crystal-Based Precursor Solutions

Summary Tin-based perovskite solar cells (PSCs), with more consummate optical band gaps, lower exciton-binding energies, and higher charge-carrier mobility, have not attracted tremendous research efforts compared with the lead-based ones that have a record power conversion efficiency (PCE) of 24.2%. The major challenges for Sn-based research are significantly low open-circuit voltage, poor reproducibility, and environmental instability. It has been identified that the oxidation processes take place during the preparation of precursor solutions and fabrication of films, due to the low redox potential of the stannous absorption layer. Herein, we propose two strategies of crystal-resolving and recrystallization technology to reduce the oxidation process. As a result, PCEs of 8.9% (active area of 0.04 cm2) and 5.5% (active area = 1.01 cm2) are attained using the inverted p-i-n structure, which will lead to a revival of lead-free PSC research.

Rapid crystallization and controllable growth of perovskite thin films via a seeded approach

Organic–inorganic hybrid perovskite solar cells (PVSCs) have attracted extensive attention due to high efficiency, easy fabrication, and low-cost solution processes. One of the keys to achieve high-performance cost-effective PVSCs is to attain rapid crystallization with controlled morphology of the perovskite films. Herein, the authors report a technique for the rapid crystallization of perovskite with tunable crystal grain size and morphology via a seeded approach. Specifically, a solution of lead iodide (PbI2) was spin coated on a substrate, and a low-concentration solution of methylammonium iodide (MAI) was dropped onto the PbI2 film to form perovskite seeds prior to introducing high-concentration solution of MAI. The seeded nucleation and growth lead to dense and uniform perovskite thin films with controllable crystal grains. This seeded crystallization technique offers an effective way to boost the low-cost manufacture of efficient and reproducible PVSCs.

Long-term stable perovskite solar cells with room temperature processed metal oxide carrier transporters

A hydrophobic electron transporter is introduced to enhance the moisture stability of perovskite solar cells (PSCs). The calcine-free deposition of carrier transporters contributes to achieving stable, scalable and reproducible PSCs with low cost.

SnO2 -in-Polymer Matrix for High-Efficiency Perovskite Solar Cells with Improved Reproducibility and Stability.

Understanding interfacial loss and the ways to improving interfacial property is critical to fabricate highly efficient and reproducible perovskite solar cells (PSCs). In SnO2 -based PSCs, nonradiative recombination sites at the SnO2 -perovskite interface lead to a large potential loss and performance variation in the resulting photovoltaic devices. Here, a novel SnO2 -in-polymer matrix (i.e., polyethylene glycol) is devised as the electron transporting layer to improve the film quality of the SnO2 electron transporting layer. The SnO2 -in-polymer matrix is fabricated through spin-coating a polymer-incorporated SnO2 colloidal ink. The polymer is uniformly dispersed in SnO2 colloidal ink and promotes the nanoparticle disaggregation in the ink. Owing to polymer incorporation, the compactness and wetting property of SnO2 layer is significantly ameliorated. Finally, photovoltaic devices based on Cs0.05 FA0.81 MA0.14 PbI2.55 Br0.45 perovskite sandwiched between SnO2 and Spiro-OMeTAD layer are fabricated. Compared with the averaging power conversion efficiency of 16.2% with 1.2% deviation for control devices, the optimized devices exhibit an improved averaging efficiency of 19.5% with 0.25% deviation. The conception of polymer incorporation in the electron transporting layer paves a way to further increase the performance of planar perovskite solar cells.

Highly reproducible perovskite solar cells via controlling the morphologies of the perovskite thin films by the solution-processed two-step method

Organic–inorganic halide perovskites are one of the most attractive materials for the next generation solar cells. The PCE has rapidly increased to more than 22% using different configurations and techniques and further developments are predicted. However, perovskite solar cells suffer from fabrication reproducibility mainly due to difficulty in controlling the morphology of the perovskite films themselves. In this paper we present a low temperature solution-processed two-step deposition method to fabricate CH3NH3PbI3 perovskites. This method offers a simple route with great potential in fabricating reproducible perovskite solar cells. In the present work, we demonstrate that the morphology of the perovskite thin films is highly determined by the concentration of Methylammonium iodide (MAI) as well as the reaction time between MAI and PbI2. High-performance solar cells have been reproducibly achieved with a highest PCE of 15.01% for PCBM-based planar heterojunction solar cells.

Highly reproducible perovskite solar cells based on solution coating from mixed solvents

Highly reproducible and enhanced-efficiency perovskite solar cells based on oriented 1D TiO2 have been successfully fabricated from DMF/DMSO mixed solvents by a simple one-step deposition method, and the whole experimental section was proceeded in the air with temperature of 25–35 °C and humidity of 40–60% without a glove box. We have specifically studied the proportion of the DMF/DMSO mixed solvents influenced on the preparation of perovskite films and the efficiency of perovskite solar cells. Another main emphasis of our work was focus on the reproducibility of the perovskite solar cells, 40 fully independent devices for each kind of solar cells have been statistically analyzed, and the main photovoltaic parameters with small standard deviation (less than 0.6 of J sc and PCE, less than 0.03 of V oc and FF) indicating that the devices have excellent reproducibility. The best-performing device fabricated from 50 wt% DMF/DMSO mixed solvents showed the average efficiency as high as 10.56% with negligible hysteresis phenomenon, which was over 95% higher than those from pure solvents. These results may provide helpful progress toward the understanding of the function of the solvents for preparing extremely high-quality perovskite films and high-reproducible perovskite solar cells in ambient air.

One-Step Printable Perovskite Films Fabricated under Ambient Conditions for Efficient and Reproducible Solar Cells.

Despite the potential of roll-to-roll processing for the fabrication of perovskite films, the realization of highly efficient and reproducible perovskite solar cells (PeSCs) through continuous coating techniques and low-temperature processing is still challenging. Here, we demonstrate that efficient and reliable CH3NH3PbI3 (MAPbI3) films fabricated by a printing process can be achieved through synergetic effects of binary processing additives, N-cyclohexyl-2-pyrrolidone (CHP) and dimethyl sulfoxide (DMSO). Notably, these perovskite films are deposited from premixed perovskite solutions for facile one-step processing under a room-temperature and ambient atmosphere. The CHP molecules result in the uniform and homogeneous perovskite films even in the one-step slot-die system, which originate from the high boiling point and low vapor pressure of CHP. Meanwhile, the DMSO molecules facilitate the growth of perovskite grains by forming intermediate states with the perovskite precursor molecules. Consequently, fully printed PeSC based on the binary additive system exhibits a high PCE of 12.56% with a high reproducibility.

Continuous Dripping Method as a Deposition Route for High-performance Mesoporous Perovskite Solar Cells

The past five years have witnessed the uniquely rapid emergence of the mixed organic-inorganic halide perovskite solar cells. Here, a modified deposition process, continuous dripping method, is reported for fabricating high-performance and reproducible perovskite solar cells. The best power conversion efficiency (PCE) of 17.76% and an average PCE of 16.74% were obtained via this process. Moreover, the conventional solution two steps method was also carried out as a comparison to this process. This work provides a new simple solution approach to obtain high quality of perovskite thin films for high-performance and reproducible PSCs.

Spin-coating free fabrication for highly efficient perovskite solar cells

A spin-coating-free fabrication sequence has been developed for the fabrication of highly efficient organic-inorganic halide perovskite solar cells (PSCs). A novel blow-drying method is demonstrated to be successful in depositing high quality mesoporous TiO2 (mp-TiO2), methylammonium lead halide (CH3NH3PbI3) perovskite and spiro-MeOTAD layers. When combined with compact TiO2 (c-TiO2) deposited by spray pyrolysis which is also a spin-coating-free process, a stabilized power conversion efficiency exceeding 17% can be achieved for the glass/FTO/c-TiO2/mp-TiO2/ CH3NH3PbI3/spiro-MeOTAD/Au device. This is the highest efficiency for PSCs fabricated without the use of spin-coating to our knowledge. This method provides a pathway towards a scalable process for fabricating high-performance, large area and reproducible PSCs.

Di-isopropyl ether assisted crystallization of organic-inorganic perovskites for efficient and reproducible perovskite solar cells.

Organic-inorganic perovskite solar cells have emerged as a promising photovoltaic technology because of their advantages such as low cost, high efficiency, and solution processability. The performance of perovskite solar cells is highly dependent on the crystallinity and morphology of the perovskite films. Herein, we report a simple, one-step anti-solvent deposition process using di-isopropyl ether as a dripping solvent to obtain extremely uniform and highly crystalline CH3NH3PbI3 perovskite films. Compared to toluene, chlorobenzene, chloroform, or diethyl ether, di-isopropyl ether has proven to be a more suitable solvent for an anti-solvent deposition process. The perovskite solar cells fabricated by the anti-solvent deposition process using di-isopropyl ether treatment exhibit an average power conversion efficiency (PCE) of 17.67 ± 0.54% and the highest PCE of 19.07%. Moreover, the higher boiling point of di-isopropyl ether makes the anti-solvent deposition process more tolerant to elevated ambient temperature, which can be carried out at ambient temperatures up to 40 °C. Our results demonstrate that di-isopropyl ether is an excellent dripping solvent in the anti-solvent deposition process for efficient and reproducible perovskite solar cells.

Crack-free CH3NH3PbI3 layer via continuous dripping method for high-performance mesoporous perovskite solar cells

The past five years have witnessed the uniquely rapid emergence of the mixed organic-inorganic halide perovskite solar cells. Here, a modified deposition process, continuous dripping method, is reported for fabricating high-performance and reproducible perovskite solar cells. We have systematically investigated the impact of different molar ratio of lead iodide (PbI2) to dimethylsulfoxide (DMSO) on the growth, morphology and crystallinity of CH3NH3PbI3 (MAPbI3) films obtained via this process. The high power conversion efficiency (PCE) perovskite solar cell originates in crack-free and highly crystallographic perovskite films prepared with optimized ratio of PbI2 to DMSO in first precursor solution. The best PCE of 17.76% and an average PCE of 16.37±0.51% were obtained via this process. Moreover, the conventional solution two steps method was also carried out as a comparison to this process. This work provides a new simple solution approach to obtain high quality of perovskite thin films for high-performance and reproducible PSCs.

Highly reproducible perovskite solar cells with excellent CH3NH3PbI3−xClx film morphology fabricated via high precursor concentration

A novel method was proposed to achieve excellent CH3NH3PbI3−xClx films based on a high concentration spinning process, which offered an effective strategy for highly reproducible perovskite solar cells with excellent morphology.

Highly Reproducible Perovskite Solar Cells with Average Efficiency of 18.3% and Best Efficiency of 19.7% Fabricated via Lewis Base Adduct of Lead(II) Iodide

High efficiency perovskite solar cells were fabricated reproducibly via Lewis base adduct of lead(II) iodide. PbI2 was dissolved in N,N-dimethyformamide with equimolar N,N-dimethyl sulfoxide (DMSO) and CH3NH3I. Stretching vibration of S═O appeared at 1045 cm(-1) for bare DMSO, which was shifted to 1020 and 1015 cm(-1) upon reacting DMSO with PbI2 and PbI2 + CH3NH3I, respectively, indicative of forming the adduct of PbI2·DMSO and CH3NH3I·PbI2·DMSO due to interaction between Lewis base DMSO and/or iodide (I(-)) and Lewis acid PbI2. Spin-coating of a DMF solution containing PbI2, CH3NH3I, and DMSO (1:1:1 mol %) formed a transparent adduct film, which was converted to a dark brown film upon heating at low temperature of 65 °C for 1 min due to removal of the volatile DMSO from the adduct. The adduct-induced CH3NH3PbI3 exhibited high charge extraction characteristics with hole mobility as high as 3.9 × 10(-3) cm(2)/(V s) and slow recombination rate. Average power conversion efficiency (PCE) of 18.3% was achieved from 41 cells and the best PCE of 19.7% was attained via adduct approach.