Improvement of performance of CsPbBr<sub>3</sub> perovskite solar cells by polyvinylidene fluoride additive

Abstract

<sec>Recently, the power conversion efficiency (PCE) of organic-inorganic hybrid perovskite solar cells has been enhanced rapidly from 3.8% to 25.8%, which is a top research topic in the field of photovoltaic power generation. However, the preparation of the hybrid perovskite solar cells has high environmental requirements, and the absorber layer is easily caused by the environmental influence and decomposition, resulting in the degradation of device performance. The all-inorganic CsPbBr<sub>3</sub> perovskite material has good stability, can be prepared directly in air, and is more economical, showing great potential applications. However, the PCE of all-inorganic CsPbBr<sub>3</sub> perovskite solar cells is not high, and at this stage, there is still much room for exploring high-quality controllable preparation of CsPbBr<sub>3</sub> films. In this paper, we aim to prepare efficient and stable CsPbBr<sub>3</sub> perovskite solar cells with additive engineering.</sec><sec>Polymer is one of the most effective additives in perovskite solar cells. The use of polymer additive in perovskite layer can improve the shape-form, structure, and band gap of the film, thus improving the quality of perovskite film. Polyvinylidene fluoride (PVDF) is a cheap polymer with hydrophobic F ions and long flexible polymer chains, and can be used to prepare efficient and stable perovskite solar cells.</sec><sec>In this paper, CsPbBr<sub>3</sub> perovskite films are prepared by multi-part spin-coating method. PVDF with enriched hydrophobic F is added into the PbBr<sub>2</sub> precursor solution as an additive to adjust the crystalline quality of the perovskite film, and the effects of PVDF on the growth process and device performance of the perovskite film are systematically studied. The results show that the PVDF can be used as a template to promote the growth of perovskite crystals, improve the crystal structure and film shape, thus reducing the defect density and charge recombination, and increasing the PCE of the device to 8.17%. The original efficiency of more than 90% can be maintained after 1400 h of storage under unencapsulated condition. Finally, high-efficiency, stable and low-cost CsPbBr<sub>3</sub> perovskite solar cells are obtained, which is important in further expanding the optimized design ideas of CsPbBr<sub>3</sub> perovskite solar cells. The PVDF can form hydrogen bonds with perovskite or interact with lead ions to improve the structural stability of perovskite, and the F ions in PVDF can improve the moisture stability of perovskite layers.</sec>