Decreasing the crystal growth time and increasing the number of nuclei produced high quality perovskite films toward large-area high-efficiency perovskite solar cells.

No abstract

Organic halide salt passivation is considered to be an essential strategy to reduce defects in state-of-the-art perovskite solar cells (PSCs). This strategy, however, suffers from the inevitable formation of in-plane favored two-dimensional (2D) perovskite layers with impaired charge transport, especially under thermal conditions, impeding photovoltaic performance and device scale-up. To overcome this limitation, we studied the energy barrier of 2D perovskite formation from ortho-, meta- and para-isomers of (phenylene)di(ethylammonium) iodide (PDEAI2) that were designed for tailored defect passivation. Treatment with the most sterically hindered ortho-isomer not only prevents the formation of surficial 2D perovskite film, even at elevated temperatures, but also maximizes the passivation effect on both shallow- and deep-level defects. The ensuing PSCs achieve an efficiency of 23.9% with long-term operational stability (over 1000 h). Importantly, a record efficiency of 21.4% for the perovskite module with an active area of 26 cm2 was achieved.

The recent dramatic rise in power conversion efficiencies (PCE) of perovskite solar cells has triggered intense research worldwide. However, their practical development is hampered by poor stability and low PCE values with large areas devices. Here, we developed a gas-pumping method to avoid pinholes and eliminate local structural defects over large areas of perovskite film, even for 5 × 5 cm2 modules, the PCE reached 10.6% and no significant degradation was found after 140 days of outdoor testing. Our approach enables the realization of high performance large-area PSCs for practical application.

A uniform and full coverage perovskite film is of significant importance for flexible perovskite solar cells.

Control of the perovskite film formation process to produce high-quality organic-inorganic metal halide perovskite thin films with uniform morphology, high surface coverage, and minimum pinholes is of great importance to highly efficient solar cells. Herein, we report on large-area light-absorbing perovskite films fabrication with a new facile and scalable gas pump method. By decreasing the total pressure in the evaporation environment, the gas pump method can significantly enhance the solvent evaporation rate by 8 times faster and thereby produce an extremely dense, uniform, and full-coverage perovskite thin film. The resulting planar perovskite solar cells can achieve an impressive power conversion efficiency up to 19.00% with an average efficiency of 17.38 ± 0.70% for 32 devices with an area of 5 × 2 mm, 13.91% for devices with a large area up to 1.13 cm(2). The perovskite films can be easily fabricated in air conditions with a relative humidity of 45-55%, which definitely has a promising prospect in industrial application of large-area perovskite solar panels.

The toxicity and the instability of lead-based perovskites might eventually hamper the commercialization of perovskite solar cells. Here, we present the optoelectronic properties and stability of a two-dimensional layered (C6H5CH2­NH3)2CuBr4 perovskite. This material has a low E g of 1.81 eV and high absorption coefficient of ∼1 × 105 cm–1 at the most intensive absorption at 539 nm, implying that it is suitable for light-harvesting in thin film solar cells, especially in tandem solar cells. Furthermore, X-ray diffraction (XRD), ultraviolet–visible (UV–vis) absorption spectra, and thermogravimetric analysis (TGA) confirm the high stability toward humidity, heat, and ultraviolet light. Initial studies produce a mesoscopic solar cell with a power conversion efficiency of 0.2%. Our work may offer some useful inspiration for the further investigation of environment-friendly and stable organic–inorganic perovskite photovoltaic materials.

The efficiencies of organic-inorganic lead halide perovskite solar cells (PSCs) have significantly increased so far, but the long-term stability of PSCs needs to be urgently improved. In this work, a novel and convenient strategy is developed to improve PSCs' stability by introducing thiourea into perovskite. Thiourea passivates perovskite by the formation of the Pb─S bond on the outermost layer of perovskite and lath-shaped grain among perovskites, which contributes to the improvement of oxygen, light, thermal stability, and little hysteresis. The mechanism is elucidated by the density functional theory calculation. In addition, the additive of thiourea into perovskite significantly improves the quality of perovskite crystal for the adduct of PbI 2 with thiourea as the Lewis base. Devices of a perovskite film with the thiourea additive achieve high efficiencies of 19.57% and 17.67% for active areas of 0.1 and 1.0 cm 2 , respectively. Most importantly, unencapsulated devices retain 98% and 93% of original efficiencies after two months under air conditions for active areas of 0.1 and 1.0 cm 2 , respectively, showing excellent stability. The present work provides a simple and effective method to improve long-term stability of PSCs.