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• A simple solvent engineering strategy was employed to control morphology of PbI 2 films effectively by water processing. • Platelet-like PbI 2 films can successfully control the residual amount of PbI 2 in perovskite film. • Platelet-like PbI 2 films can control the morphology of the perovskite film and improve the device efficiency [Display omitted] The performance of organic-inorganic perovskite solar cells depends largely on the quality of perovskite film. Currently, various methods are applied to prepare the perovskite film. Among them, the two-step method is counted as a promising candidate to obtain high-quality perovskite film. In this study, we attain a special platelet-like PbI 2 films by applying pure water to cover wet PbI 2 film and standing for a period of time. The unique morphology contributes to the entry of organic cations solution into the PbI 2 and promoting its reaction with PbI 2 , which reducing the residual amount of PbI 2 in the perovskite film. Compared to the traditional two-step method, water processing method can obtain a high-quality perovskite film with enlarged grain size, improved crystallization, and prolonged carrier lifetime. As a result, the efficiency of the prepared device based on the film has increased from 17.90% without water processing to 20.14% of water processing. Which demonstrates that this solvent engineering for PbI 2 film opens up a possibility to prepare high-quality perovskite in a two-step method and obtain highly efficient perovskite solar cells. [ABSTRACT FROM AUTHOR]

High coverage film could be obtained from precursor film PEDOT: PSS-based inverted perovskite solar cell, via decreasing the amount of residual DMSO or mediating the evaporation rate of DMSO with continuous gradient annealing (GA) process at 65°C–85°C (heating rate of 20°C/5 min). • A remanent solvent management strategy was employed to prepare uniform film. • The influence of residual DMSO on the properties of the MAPbI 3 film was investigated. • High device reproducibility was obtained with gradient thermal annealing. Perovskite solar cells (PSCs) have been attracting tremendous attention due to ease of processing, flexibility, and high performance. Dimethyl sulfoxide (DMSO) and N, N-dimethylformamide (DMF) are the two most widely used solvents to dissolve perovskite precursors. Here, we investigate the impact of residual amount and evaporation rate of the DMSO inside the precursor films on the microstructure of the ultimate perovskite films. We decouple the DMSO and DMF solvents and demonstrate that DMSO component exhibits great and dominant influence on the final film morphology by using quasi in-situ photoluminescence (PL) measurement and X-ray diffraction (XRD) characterization of the wet films after spin-coating. Much more smooth and uniform perovskite films are obtained by careful management of remanent solvent, including decreasing residual amount by shelving the precursor films prior to heating and retarding the evaporation of the solvent via adopting a gradient annealing (GA) process. In consequence, the as-prepared PEDOT: PSS-based inverted PSCs yield a champion efficiency of 15.59% with high reproducibility. This work shows great potential in preparing high-quality perovskite films through a simple remanent solvent management engineering. [ABSTRACT FROM AUTHOR]

Solution-processed Cu-doped SnO 2 as an effective electron transporting layer for high-performance planar perovskite solar cells are systematically studied. The energy-level of SnO 2 electron transporting layer and the crystallization of CsFAMA films exhibit dramatically different evolution trends with respect to the addition of copper. The replacement of Sn ions by copper ions in the materials result in an improvement in conductivity of Cu-doped SnO 2 , further improve the current density of the corresponding devices. A little bit of p-type CuO does a lot for SnO 2 electron transport layer and their solar cells are firstly demonstrated. [Display omitted] • The Cu-doped SnO 2 has been successfully achieved, which results in the enhanced conductivity and improved energy band position for the Cu: SnO 2 electron transport layer. • A better quality of perovskite film with enhanced crystallinity and enlarged grain size was obtained. • The doping concentration of 5 mol% was desirable for the fabricated CsFAMA solar cells with a champion PCE of 21.35%. • The PSCs device based on Cu: SnO 2 ETL delivers excellent stability under continuous light or thermal conditions. A high-quality electron transport layer (ETL) is indispensable for effective and stable planar perovskite solar cells (PSCs). Tin oxide (SnO 2) is considered the most promising alternative to TiO 2 as ETL due to its excellent optical and electrical properties. However, some of improvements need to be carried out for intrinsic SnO 2 , such as conductivity, energy loss, and lattice mismatch in the SnO 2 /perovskite interface. Herein, the Cu-doped SnO 2 (Cu: SnO 2) as ETL has been made through mixing the copper salt precursor solution with SnO 2 colloidal solution in room-temperature solution-processed. The Cu incorporated into SnO 2 increases the conductivity of ETL and uplifts the conduction band to obtain a more suitable band alignment in SnO 2 /perovskite interface for relieving the energy barrier in the charge transporting. Moreover, it further improves the quality of perovskite films with the enhanced crystallinity, enlarged grain size, which have an impact on light absorption and reduction of defect states for the perovskite layer. The power conversion efficiency (PCE) of the prepared planar PSCs with Cu:SnO 2 ETL exceeds 21%, compared with the SnO 2 -based PSCs (19.63%), and the long-term stability was improved. [ABSTRACT FROM AUTHOR]