Amorphous polymer with CO to improve the performance of perovskite solar cells

Abstract

Morphology and crystallinity of perovskite layers are crucial for power conversion efficiency (PCE) of perovskite solar cells (PSCs). Here, we introduced amorphous polymer polyvinylpyrrolidone (PVP) with a CO functional group into a CH₃NH₃PbI_3−xCl_x perovskite precursor to tune the morphology and crystallinity of perovskite layers during the film formation process. The spreading amorphous polymer chains and excellent hygroscopicity of PVP can help the perovskite precursor have better contact with the substrate, leading to better perovskite film coverage. More importantly, the electron pair existing in the oxygen atom of the CO bond in PVP has a strong attraction to Pb(II) ions, which can adjust the location of the nuclei and make the nuclei distribute uniformly in PVP chains, contributing to a uniform and compact perovskite layer. As a result, perovskite films with PVP present favourable morphology and improved crystallinity. The performance of a CH₃NH₃PbI_3−xCl_x-based perovskite solar cell with optimized PVP content achieves a summit PCE of 16.57% with photovoltage V_OC of 1057 mV, short circuit current density J_SC of 21.38 mA cm⁻², and fill factor FF of 74.52% under standard AM 1.5 solar light of 100 mW cm⁻² intensities, which demonstrates a 23.9% increment compared with a PCE of 13.37% of the original device.