Fabrication Of Perovskite Solar Cells Research Articles

The effect of pyrrolidone-based ligands in gas-quenching fabrication of FA0.9Cs0.1PbI3 perovskite films and solar cells

Gas-quenching fabrication of perovskite films demonstrates promising compatibility for commercialization of perovskite photovoltaics. Seeking suitable ligand for the perovskite precursor inks to improve the crystalline quality of gas-quenched methylammonium free perovskite films is critical for realizing up-scalable fabrication of stable perovskite solar cells. In this work, a series of pyrrolidone-based ligands are employed in gas-quenching fabrication of FA0.9Cs0.1PbI3 perovskite films. Optical and morphological characterizations indicate 2-pyrrolidone is the most preferred ligand to deliver a neat buried-interface as well as a light-trapping surface at the rear of the device, which maximized the light-harvesting and the photocurrent of the device. The corresponding device achieved a power conversion efficiency of 21.6% without any interfacial passivation, as well as reduced defect density from their electrical characteristics. Moreover, a more stable performance of the device is obtained with 2-pyrrolidone compared to other pyrrolidone-based ligands, demonstrating 2-pyrrolidone as a promising ligand in designing the perovskite inks for methylammonium-free perovskite solar cells.

Water-Regulated Lead Halide Perovskites Precursor Solution: Perovskite Structure Making and Breaking

Identifying the impact of water on iodoplumbate complexes in various solutions is essential for linking the coordination environment of the perovskite precursor to its final perovskite solar cell (PSC) properties. In this study, we propose a digital twin approach based on X-ray absorption fine structure and molecular dynamic simulation to investigate the structure evolution of iodoplumbate complexes in precursor solutions as a function of storage time under a constant humidity environment. A full picture about what water does in the perovskite formation process is brought out, and the “making and breaking” role of water molecules is uncovered to link the structure of iodoplumbate complexes to its final properties. This study sheds light on a full picture about what water does in the perovskite formation process and the role of water, which will lead to developing water-involved strategies for consistent PSC fabrication under ambient conditions.

Improving Crystallization and Stability of Perovskite Solar Cells Using a Low-Temperature Treated A-Site Cation Solution in the Sequential Deposition.

The two-step sequential deposition is a commonly used method by researchers for fabricating perovskite solar cells (PSCs) due to its reproducibility and tolerant preparation conditions. However, the less-than-favorable diffusive processes in the preparation process often result in subpar crystalline quality in the perovskite films. In this study, we employed a simple strategy to regulate the crystallization process by lowering the temperature of the organic-cation precursor solutions. By doing so, we minimized interdiffusion processes between the organic cations and pre-deposited lead iodide (PbI2) film under poor crystallization conditions. This allowed for a homogenous perovskite film with improved crystalline orientation when transferred to appropriate environmental conditions for annealing. As a result, a boosted power conversion efficiency (PCE) was achieved in PSCs tested for 0.1 cm2 and 1 cm2, with the former exhibiting a PCE of 24.10% and the latter of 21.56%, compared to control PSCs, which showed a PCE of 22.65% and 20.69%, respectively. Additionally, the strategy increased device stability, with the cells holding 95.8% and 89.4% of the initial efficiency even after 7000 h of aging under nitrogen or 20-30% relative humidity and 25 °C. This study highlights a promising low-temperature-treated (LT-treated) strategy compatible with other PSCs fabrication techniques, adding a new possibility for temperature regulation during crystallization.

Fast Solidification and Slow Growth Strategy for High‐Performance Quasi‐2D Perovskite Solar Cells (Adv. Energy Mater. 17/2023)

Perovskite Solar Cells In article number 2300168, Weifei Fu, Yingguo Yang, Lijian Zuo, Hongzheng Chen, and co-workers take advantage of the synergism of low-boiling point solvents and high-boiling point additives, to easily spin coat a high-quality perovskite film within 3 seconds. This strategy avoids the dripping of anti-solvent, which is especially suitable for the fabrication of up-scaled perovskite solar cells.

Development of Perovskite (MACl)0.33FA0.99MA0.01Pb(I0.99Br0.01)3 Solar Cells via n-Octylammonium Iodide Surface Passivation.

The influence of n-octylammonium iodide (OAI, passive layer) on the types of phases formed in a (MACl)0.33FA0.99MA0.01Pb(I0.99Br0.01)3 perovskite film was studied using X-ray diffraction. Using UV spectrophotometric techniques, it was determined how varied OAI additive layer ratios affected the linear and nonlinear optical characteristics of glass substrates/FTO/compact TiO2/mesoporous TiO2/(MACl)0.33FA0.99MA0.01Pb(I0.99Br0.01)3 films. All films' direct optical bandgap energies were determined to be 1.54 eV. The effects of OAI addition on the films' photoluminescence intensity and emitted colors were also investigated. For the fabricated perovskite solar cells (PSCs) without an OAI passivation layer, the corresponding power conversion efficiency (PCE), open-circuit voltage (VOC), short-circuit current density (JSC), and fill factor (FF) values were 18.8%, 1.02 V, 24.6 mAcm-2, and 75%, respectively. When the concentration of OAI reached 2 mg, the maximum obtained values of PCE, VOC, JSC, and FF were 20.2%, 1.06 V, 24.2 mAcm-2, and 79%, respectively. The decreased trap density and increased recombination resistance were responsible for the improvement in solar cell performance.

Fabrication of inverted planar perovskite solar cells using the iodine/ethanol solution method for copper iodide as a hole transport layer

Copper iodide (CuI) is under extensive research due to its low cost, easy fabrication process, and wide bandgap. This research includes the fabrication of perovskite solar cells using the p–i–n structure (inverted structure) with a focus on the hole transport layer (HTL) layer. In this paper, we demonstrate the applicability of using CuI as a HTL in perovskite solar cells using the iodine/ethanol solution method. Using the iodine/ethanol solution for preparing the CuI, a power conversion efficiency of 0.76%, a short-circuit current density of 4.56 mA cm−2, an open-circuit voltage of 0.494 V as well as a fill factor of 0.34 were obtained. The overall performance of the solar cell still requires much improvement. We have successfully deposited the CuI using RF magnetron sputtering and the iodine/ethanol solution method and understand that the low performance of the device is mainly due to the voids and gaps present within the CuI layer.

Improving parameters of inorganic perovskite solar cells by more than one spin coating method

This work reports the fabrication process for preparation of perovskite films with good quality morphology and optimal thickness by a simple process of more than one spin coating or multiple spin coating (MSC) method. It should be noted that perovskite films with good quality morphology and optimal thickness are prepared without antisolvent engineering in full air conditions. In this work, we obtained an optimal good power conversion efficiency (PCE) value for CsPbI3 perovskite solar cells (PSCs) at 11.69%. Although, the PCE result is not high enough, however, this MSC method provides a simple and uncomplicated approach for fabrication of PSCs. (PCE) value for at 11.69%. CsPbI3.

Highly Stable n–i–p Structured Formamidinium Tin Triiodide Solar Cells through the Stabilization of Surface Sn2+ Cations

AbstractImproving the performance, reproducibility, and stability of Sn‐based perovskite solar cells (PSCs) with n–i–p structures is an important challenge. Spiro‐OMeTAD [2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenyl‐amine)9,9′‐spirobifluorene], a hole transporting material (HTM) with n–i–p structure, requires the oxygen exposure after addition of Li‐TFSI [Lithium bis(trifluoromethanesulfonyl)imide] as a dopant to increase the hole concentration. In Sn‐based PSC, Sn2+ is easily oxidized to Sn4+ under such a condition, resulting in a sharp decrease in efficiency. Herein, a formamidinium tin triiodide (FASnI3)‐based PSCs fabricated using DPI‐TPFB [4‐Isopropyl‐4′‐methyldiphenyliodonium tetrakis(pentafluorophenyl)borate] instead of Li‐TFSI are reported as a dopant in Spiro‐OMeTAD. The DPI‐TPFB enables the fabrication of PSCs with an efficiency of up to 10.9%, the highest among FASnI3‐based PSCs with n–i–p structures. Moreover, ≈80% of the initial efficiency is maintained even after 1,597 h under maximum power point tracking conditions. In particular, the encapsulated device does not show any decrease in efficiency even after holding for 50 h in the 85 °C/85% RH condition. The high efficiency and excellent stability of PSCs prepared by doping with DPI‐TPFB are attributed to not only increasing electrical conductivity by acting as a Lewis acid, but also stabilizing Sn2+ through coordination with Sn2+ on the surface of FASnI3.

Additives and interface engineering facilitate the fabrication of high-efficiency perovskite solar cells in ambient air-processed

Additives and interface engineering facilitate the fabrication of high-efficiency perovskite solar cells in ambient air-processed

Laterally Grown Strain-Engineered Semitransparent Perovskite Solar Cells with 16.01% Efficiency

Hybrid organometallic halide perovskite-based semitransparent solar cell research has garnered significant attention recently due to their promising applications for smart windows, tandem devices, wearable electronics, displays, and sustainable internet-of-things. Though considerable progress has been made, stability, controlling the crystalline qualities, and growth orientation in perovskite thin films play crucial roles in improving the photovoltaic (PV) performance. Recently, strain modulation within the perovskite gathers an immense interest that is achieved by the ex situ process. However, little work is reported on in situ strain modulation, which is presented here. Apart from the challenges in the fabrication of high-efficiency perovskite solar cell (PSC) devices under ambient conditions, the stability of organic hole-transporting materials needs urgent attention. Herein, a single-step deposition of formamidiniumchloride (FACl)-mediated CH3NH3PbI3 (MAPbI3) thin films without an inert atmosphere and CuI as the inorganic hole-transporting material is demonstrated for their potential application toward semitransparent PSCs. The FACl amount in MAPbI3 (mg/mL) plays a critical role in controlling the crystallinity, growth orientations, and in situ strains, which modulate the charge carrier transport dynamics, thereby improving the efficiency of the PSC device. A photoconversion efficiency of 16.01% has been achieved from MAPbI3 with 20 mg/mL of FACl additive incorporation. The modification of the structural, electronic, and optical properties and the origin of strain in the as-synthesized MAPbI3 domains due to the addition of FACl are further validated with experimental findings in detail using density functional theory simulations.

Polymer‐Assisted Heterogeneous Lead Iodide in a Two‐Step Process: Fabrication of Efficient and Stable Perovskite Solar Cells

Developing pinhole‐free, superior crystal, and high‐quality perovskite films by regulating the lead iodide microstructure in two‐step sequential deposition has attracted increased interest in the domain of perovskite solar cells (PSCs) for commercial applications. Herein, a multifunctional polymer, polyvinyl alcohol (PVA), is incorporated into a two‐step sequential deposition process to regulate morphological transform of PbI2 and then the high‐quality perovskite films are obtained. PVA as a scaffold combines with uncoordinated Pb2+ in the PbI2 precursor solution through a strong Pb–O interaction, leading to rough PbI2. In the second step, the uneven and heterogeneous PbI2 allows FA&MA permeation and then drives adequate coordination reactions between PbI64− octahedron and bulky cations. Furthermore, the PVA gathering at grain boundary passivates redundant Pb2+ by the PbO bonding interactions in the final polycrystalline films. Consequently, high‐quality (FAPbI3)0.90(MAPbBr3)0.10 perovskite layers are obtained with promoted crystal growth, inhibited voids formation/delamination, and thus reduced trap states. The universality and versatility of this strategy not only enables improved power conversion efficiencies of 22.81% (Ag‐based devices) and 16.58% (carbon‐based devices) across architectures but also remarkedly enhances the device stability in ambient‐air aging condition, which delivers a facile and broadly applicable additive synergetic strategy for efficient and stable PSCs.

Review on Carbazole-Based Hole Transporting Materials for Perovskite Solar Cell

Solar cells constructed with organic–inorganic metal halide perovskite is a hot topic as they can replace the existing traditional silicon-based solar cells. The major hurdle in the commercialization of perovskite solar cells is the efficiency of the device. In this context, the use of a suitable organic hole transporting material would improve the efficiency of the perovskite solar cells. Until now, spiro-OMeTAD (2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene) is the standard hole transporting material (HTM) used in the fabrication of perovskite solar cells, and the major issue associated with spiro-OMeTAD is the complex multistep synthesis and the observed difficulty in the purification steps which make this HTM as cost-ineffective. Nowadays, certain hole transporting materials made up of organic small molecules carrying motifs like thiophene, triphenylamine, triazatruxane, pyrene, and carbazole exhibited better photovoltaic properties and less costs are involved for their synthesis, which motivate the researchers to work further on the design and development of non-spiro-OMeTAD. Among the various organic small molecule based HTMs, carbazole unit based HTMs exhibited better photovoltaic properties, chemical stability, easy functionalization, and device performance. Thus, the present review mainly focused on the diverse carbazole-based hole transporting molecular designs and their synthetic strategies which have been reported during the past eight years. Also, the review tries to correlate the molecular structure of different carbazole-based HTMs and their observed energy band gap, HOMO–LUMO levels, hole mobilities, and power conversion efficiencies for the fabricated perovskite solar cells.

Fast Solidification and Slow Growth Strategy for High‐Performance Quasi‐2D Perovskite Solar Cells

AbstractSmooth perovskite film with high crystallinity and vertical orientation is highly favored for high‐performance quasi‐2D perovskite solar cells (PVSCs), yet limited by the critical balance between nucleation and crystal growth. To address this issue, here a fast solidification and slow growth (FSSG) strategy is developed to effectively optimize the film morphology. The fast solidification enables a smooth, pinhole‐free film, while slow growth allows it to further ripen into high‐crystallinity film. This process is enabled by the low‐boiling point solvent system, that is, acetonitrile, with high‐boiling point additives, that is, NH4SCN and CH3NH3Cl. Compared to the traditional method, uniform film with a larger grain/crystallite size as well as better crystallinity can be easily fabricated through this FSSG strategy. As a result, the quasi‐2D PVSCs based on (GA)2(MA)4Pb5I16 processed with the FSSG strategy show a champion power conversion efficiency of 20.44%, as well as 19.08% for large‐area (1 cm2) devices, which suggest the capability of the FSSG strategy for up‐scaled PVSC fabrication. Therefore, this work opens a new avenue toward morphology control of PVSCs for practical applications.

Radical reinforced defect passivation strategy for efficient and stable MAPbI3 perovskite solar cells fabricated in air using a green anti-solvent process

Compared with traditional processes for perovskite solar cell (PSC) fabrication using toxic anti-solvents in an inert environment, the air process using a green anti-solvent is significantly more eco-friendly and economical. However, such perovskite films contain more defects owing to moisture and non-optimal anti-solvents. To solve this problem, a new radical-strengthened defect passivation strategy is proposed, for enhancing the electron density of Lewis bases to reduce defect states in perovskite films. By introducing a donor–acceptor structure and free radical to improve the electron donation ability of Cl groups, a stable radical derivative (OTTM) with methoxy and multiple Cl groups was designed and used as a green anti-solvent additive for perovskite passivation. The mechanisms of radical-enhanced defect passivation are uncovered by theoretical and experimental results. As a consequence, a 21% power conversion efficiency with high stability was achieved based on the air process with a green anti-solvent for MAPbI3 PSCs.

Topical advances in fabrication technologies of perovskite solar cell heterostructures: Performance and future perspective

Organic-inorganic hybrid perovskite light-harvesting materials are becoming one of the most capable potential contenders in photovoltaic technology because of their low-cost fabrication, ease of processing, and high power conversion efficiency (PCE). However, it is still challenging to extend these perovskite materials with a cost-effective fabrication technique to meet the demand for roll-to-roll manufacturing and mass production. Several fabrication methods have been developed and tested with different device configurations to enhance properties like device stability and photon-to-current conversion efficiency. The quality of thin-films has a vital role in determining the suitable fabrication method and appropriate structure to improve the overall performance of perovskite devices. This review article summarizes various deposition techniques used in fabrication of perovskite solar cells (PSCs), device technologies for perovskite light-absorbing heterostructures and future research perspectives.

Importance of Low Humidity and Selection of Halide Ions of Octylammonium Halide in 2D–3D Perovskite Solar Cells Fabricated in Air

AbstractAir fabrication of efficient and stable perovskite solar cells with substantial reproducibility is of importance for commercialization of perovskite solar cells. There has been little consensus on which halide is the best selection for thin 2D perovskite layer on 3D perovskite when processing in ambient air. In this work, the influence of humidity and halide ions in alkylammonium halide (OAX)‐treated perovskite layer on photovoltaic performance is investigated. The authors find that a combination of high humidity and the presence of chloride ions can induce the deprotonation of methylammonium (MA+) ions. With X‐ray diffraction, cross‐sectional scanning electron microscope, Fourier‐transform infrared spectroscopy, the authors elucidate that the deprotonation reaction in the octylammonium chloride (OACl)‐treated perovskite layer makes MA+ ions (CH3NH3+) volatile MA (CH3NH2), which results in void volumes and defects in the bulk of perovskite layer as well as at the interface. The defective perovskite solar cells induced by the deprotonation reaction have the suppressed hole transfer at the interface between the perovskite layer and the hole transport layer, yielding the reduced internal quantum efficiency and JSC. Space charge‐limited current analysis reveals that the reduced VOC is caused by the high trap density estimated from VTFL of hole‐only devices.

Uncovering the Role of Electronic Doping In Lead-free Perovskite (CH3NH3)2CuCl4-xBrx and Solar Cells Fabrication

Uncovering the Role of Electronic Doping In Lead-free Perovskite (CH3NH3)2CuCl4-xBrx and Solar Cells Fabrication

A promising scalable bar coating approach using a single crystal-derived precursor ink for high-performance large-area perovskite solar cells

Perovskite solar cells (PSCs), with demonstrated high efficiencies in a lab scale, are regarded as potential energy-harvesting materials if the challenges like large-area manufacturing and long-term stability are achieved. In an effort to fabricate PSCs on large-area substrates, the study herein reports the use of an economic and scalable bar coating method for the fabrication of PSCs. Bar coating is used initially to coat electron transport layers on large-area (50 mm × 50 mm) FTO glass substrates. A methyl ammonium lead iodide (MAPbI3) perovskite absorber has been bar coated on the electron transport layers coated FTO glass substrates using a single-crystal-derived perovskite precursor. The single crystal-derived precursor has resulted in large-area uniform perovskite absorbers and, thus, characterized appositely to establish the uniform coverage of desired quality MAPbI3. The spatial distribution of photoluminescence and absorption spectra of the perovskite absorber, collected systematically, confirms the device quality MAPbI3, with identical characteristics ascertaining the homogeneity of perovskite coating. Solar cells fabricated using bar-coated large-area perovskite absorbers have exhibited a champion power conversion efficiency of 15.6%, with the average power conversion efficiency being 14.5%, unveiling an excellent performance homogeneity. Further, the champion devices of bar-coated PSCs are compared with control devices fabricated by spin coating of a powder-derived precursor. Bar-coated PSCs have not only exhibited significantly higher performance but also showed comparable reproducibility and much lower hysteresis values than the control PSCs, demonstrating the efficacy of the bar coating method towards fabricating large-area PSCs.

Controlled growth of perovskite layers with volatile alkylammonium chlorides.

Controlling the crystallinity and surface morphology of perovskite layers by methods such as solvent engineering1,2 and methylammonium chloride addition3-7 is an effective strategy for achieving high-efficiency perovskite solar cells. In particular, it is essential to deposit α-formamidinium lead iodide (FAPbI3) perovskite thin films with few defects due to their excellent crystallinity and large grain size. Here we report the controlled crystallization of perovskite thin films with the combination of alkylammonium chlorides (RACl) added to FAPbI3. The δ-phase to α-phase transition of FAPbI3 and the crystallization process and surface morphology of the perovskite thin films coated with RACl under various conditions were investigated through in situ grazing-incidence wide-angle X-ray diffraction and scanning electron microscopy. RACl added to the precursor solution was believed to be easily volatilized during coating and annealing owing to dissociation into RA0 and HCl with deprotonation of RA+ induced by RA⋯H+-Cl- binding to PbI2 in FAPbI3. Thus, the type and amount of RACl determined the δ-phase to α-phase transition rate, crystallinity, preferred orientation and surface morphology of the final α-FAPbI3. The resulting perovskite thin layers facilitated the fabrication of perovskite solar cells with a power-conversion efficiency of 26.08% (certified 25.73%) under standard illumination.

Process Insights into Perovskite Thin‐Film Photovoltaics from Machine Learning with In Situ Luminescence Data

Large‐area processing remains a key challenge for perovskite solar cells (PSCs). Advanced understanding and improved reproducibility of scalable fabrication processes are required to unlock the technology's economic potential. In this regard, machine learning (ML) methods have emerged as a promising tool to accelerate research and unlock the control needed to produce large‐area solution‐processed perovskite thin films. However, a suitable dataset allowing the analysis of a scalable fabrication process is currently missing. Herein, a unique labeled in situ photoluminescence (PL) dataset for blade‐coated PSCs is introduced and explored with unsupervised k‐means clustering, demonstrating the feasibility to derive meaningful insights from such data. Correlations between the obtained clusters and the measured performance of PSC reveal that the in situ PL signal encodes information about the perovskite thin‐film quality. Detrimental mechanisms during thin‐film formation are detected by identifying spatial differences in PL patterns and, consequently, of device performance. In addition, k‐nearest neighbors is applied to predict the performance of PSCs, motivating further investigations into ML‐based in‐line process monitoring of scalable PSC fabrication to detect, understand, and ultimately minimize process variations across iterations.