Rapid and sheet-to-sheet slot-die coating manufacture of highly efficient perovskite solar cells processed under ambient air

Abstract: Hybrid organic–inorganic halide perovskite based solar cell technology has passed through a phase of unprecedented growth in the efficiency scale from 3.8% to above 25% within a decade. This technology has drawn tremendous research interest because of facile solution processability, ease of large scale manufacturing and ultra-low cost production of perovskite based thin film solar cells. It has been observed that performances of perovskite-based solar cells are extremely dependent on the morphology and crystallinity of the perovskite layer. The high-quality perovskite films have made a significant impact on the fabrication of efficient and stable hybrid perovskite solar cells. It has also been observed that device lifetime depends on the perovskite morphology; devices with larger perovskite grains degrade slowly than those of the smaller ones. Various methods of perovskite growth such as sequential deposition, doctor blading, slot die coating and spray coating have been applied to achieve the most appropriate morphology necessary for highly efficient and stable solar cells. This review focuses on the recent progress in morphology optimizations by various processing condition such as annealing condition, additive effects, Lewis acid–base adduct approach, precursor solution aging and post-device ligand treatment emphasizing on grain sizes, film uniformity, defect passivation, ambient compatibility and device efficiency and stability. In this review, we also discussed recently developed bifacial stamping technique and deposition methods for large-area and roll-to-roll fabrication of highly efficient and stable perovskite solar cells.

Abstract: In this work, we report perovskite solar cells in the planar p–i–n configuration based on single-step, anti-solvent-free, low-temperature (70 °C) slot-die-coated methylammonium lead tri-iodide (MAP...

Abstract: To make perovskite solar cells an industrially relevant technology large area deposition techniques are needed and one of the most promising is slot-die coating. This review article details the progress reported in the literature where slot-die coating has been used for the deposition of both the perovskite layer and other layers in the perovskite solar cell device stack. An overview of the methods used to adapt the coating process, materials and drying conditions in order to create high quality layers and devices is given and an outlook on future research directions in this field is made.

Abstract: Perovskite solar cells (PSCs) are considered the next-in-line technology in the solar industry. This technology can reduce the cost of solar energy to an unprecedented level given their remarkably high efficiency and ease of manufacturing. Hitherto, many studies have preferred well-regulated inert conditions or a low-humidity atmosphere (relative humidity < 30%) for fabricating highly efficient PSCs to avoid the adverse impact of humidity on a perovskite film. This is because humidity is the main reason for perovskite instability and can alter the film growth kinetics during the fabrication process, thereby ultimately affecting the morphology of the grown film and the device performance. The requirement for an inert or low-humidity environment can increase the capital costs of setting up the fabrication facilities and hamper the large-scale production of PSCs. Therefore, efforts have been devoted to preparing PSC devices in a high-humidity environment to comprehend perovskite crystal growth kinetics and improve the morphological properties and stability of the perovskite film. This review highlights the modifications implemented towards (1) perovskite materials, (2) charge-selective layers, and (3) deposition protocols by spin-coating, to adapt a high-humidity atmosphere (RH ≥ 30%) for developing efficient PSCs. The progress of scalable processing methods such as blade-coating, inkjet printing, slot-die coating, and spray-coating, and the translation of spin-coating-modified protocols into these methods are also discussed. Finally, this review provides the remaining challenges to realizing the high-humidity fabrication of PSCs for commercialization.

Abstract: Lead halide perovskite solar cells (PVSCs) have potential toward commercialization because of their high efficiency and low cost. The hole transport layer (HTL) of p-i-n perovskite solar cell is usually made of NiOX. However, the NiOX needs to be processed at 300 °C for 15 min for good hole transport property. This long heating time prohibits the development of continuous commercial process. Thus, a rapid heating process for the NiOX film deposition is critical to realize the commercialization of PVSCs in the future. In this study, we develop a facile method to obtain high quality NiOX films annealed by NIR in a short time of 50 s. A short-wave NIR lamp at 2500 K was used to systematically investigate the effect of NIR intensity on the film quality of sol-gel NiOX. The PVSCs fabricated from NIR-annealed NiOX (NIR-NiOX) film show a comparable power conversion efficiency (PCE) to those fabricated from traditional hot-plate annealed-NiOX (HP-NiOX). In addition, the NIR annealed cobalt-doped NiOX (NIR-Co:NiOX) was synthesized to replace pristine NIR-NiOX. The PCE of PVSCs fabricated from this new NiOX film can be increased from 15.99% to 17.77%, which is due to the efficient hole extraction, less charge accumulation, and reducing Voc loss resulting from the improved hole mobility, reduced interface resistance and well-matched work function. Our study paves a way to fulfill the requirements of low cost and low energy consumption of large scale production of high efficiency PVSCs.

Abstract: Two organolead halide perovskite nanocrystals, CH3NH3PbBr3 and CH3NH3PbI3, were found to efficiently sensitize TiO2 for visible-light conversion in photoelectrochemical cells. When self-assembled on mesoporous TiO2 films, the nanocrystalline perovskites exhibit strong band-gap absorptions as semiconductors. The CH3NH3PbI3-based photocell with spectral sensitivity of up to 800 nm yielded a solar energy conversion efficiency of 3.8%. The CH3NH3PbBr3-based cell showed a high photovoltage of 0.96 V with an external quantum conversion efficiency of 65%.

Abstract: Organic-inorganic perovskites have shown promise as high-performance absorbers in solar cells, first as a coating on a mesoporous metal oxide scaffold and more recently as a solid layer in planar heterojunction architectures. Here, we report transient absorption and photoluminescence-quenching measurements to determine the electron-hole diffusion lengths, diffusion constants, and lifetimes in mixed halide (CH3NH3PbI(3-x)Cl(x)) and triiodide (CH3NH3PbI3) perovskite absorbers. We found that the diffusion lengths are greater than 1 micrometer in the mixed halide perovskite, which is an order of magnitude greater than the absorption depth. In contrast, the triiodide absorber has electron-hole diffusion lengths of ~100 nanometers. These results justify the high efficiency of planar heterojunction perovskite solar cells and identify a critical parameter to optimize for future perovskite absorber development.

Abstract: Organic-inorganic perovskites have shown promise as high-performance absorbers in solar cells, first as a coating on a mesoporous metal oxide scaffold and more recently as a solid layer in planar heterojunction architectures. Here, we report transient absorption and photoluminescence-quenching measurements to determine the electron-hole diffusion lengths, diffusion constants, and lifetimes in mixed halide (CH3NH3PbI(3-x)Cl(x)) and triiodide (CH3NH3PbI3) perovskite absorbers. We found that the diffusion lengths are greater than 1 micrometer in the mixed halide perovskite, which is an order of magnitude greater than the absorption depth. In contrast, the triiodide absorber has electron-hole diffusion lengths of ~100 nanometers. These results justify the high efficiency of planar heterojunction perovskite solar cells and identify a critical parameter to optimize for future perovskite absorber development.

Abstract: Advancing perovskite solar cell technologies toward their theoretical power conversion efficiency (PCE) requires delicate control over the carrier dynamics throughout the entire device. By controlling the formation of the perovskite layer and careful choices of other materials, we suppressed carrier recombination in the absorber, facilitated carrier injection into the carrier transport layers, and maintained good carrier extraction at the electrodes. When measured via reverse bias scan, cell PCE is typically boosted to 16.6% on average, with the highest efficiency of ~19.3% in a planar geometry without antireflective coating. The fabrication of our perovskite solar cells was conducted in air and from solution at low temperatures, which should simplify manufacturing of large-area perovskite devices that are inexpensive and perform at high levels.

Abstract: The band gap of formamidinium lead iodide (FAPbI3) perovskites allows broader absorption of the solar spectrum relative to conventional methylammonium lead iodide (MAPbI3). Because the optoelectronic properties of perovskite films are closely related to film quality, deposition of dense and uniform films is crucial for fabricating high-performance perovskite solar cells (PSCs). We report an approach for depositing high-quality FAPbI3 films, involving FAPbI3 crystallization by the direct intramolecular exchange of dimethylsulfoxide (DMSO) molecules intercalated in PbI2 with formamidinium iodide. This process produces FAPbI3 films with (111)-preferred crystallographic orientation, large-grained dense microstructures, and flat surfaces without residual PbI2. Using films prepared by this technique, we fabricated FAPbI3-based PSCs with maximum power conversion efficiency greater than 20%.