Improving efficiency and stability of organic-inorganic hybrid perovskite solar cells by absorption layer ion doping

Abstract

ABX<sub>3</sub> crystalline perovskite material has many advantages: good photoelectric absorption property, high charge carrier mobility, good film formation, long charge carrier lifetime, and easy bandgap adjustment for absorption layer of perovskite solar cells. As a result, the power conversion efficiency (PCE) of the organic-inorganic halide perovskite solar cells (PSCs) has taken a tremendous step forward, from 3.9% in 2009 to a recently reported value over 25.5%. Thus, it shows great potential to compete with traditional silicon solar cells. However, PSCs preparing conditions are harsh and susceptible to environmental influences, thus leading to instability. Therefore, it is essential to prepare high-performance and stable PSCs in an air environment. This study aims to use the ion doping method to improve the performance and stability of PSCs and analyze the mechanism. This work focuses on enhancing PSCs efficiency and stability by performing FA<sup>+</sup> and Cl<sup>–</sup> doping experiments on MAPbI<sub>3</sub> films in air. The results show that a single Cl<sup>–</sup>-doping increases the carrier diffusion length, reducing the recombination of electrons and holes, and inducing the perovskite intermediate hydrate (CH<sub>3</sub>NH<sub>3</sub>)<sub>4</sub>PbI<sub>6</sub>·2H<sub>2</sub>O to form, promoting the crystallization of the thin film, and improving the device performance. On the other hand, a single FA<sup>+</sup>-doping will reduce the bandgap of perovskite and increase the short-circuit current density (<i>J</i><sub>SC</sub>) of the device, and FA<sup>+</sup> is susceptible to the influence of water vapor to induce a yellow <i>δ</i>-FAPbI<sub>3</sub> perovskite film to form, which leads the device performance to degrade. However, the prepared co-doping Cl<sup>–</sup>, FA<sup>+</sup> significantly improves overall PSCs device performance, yielding the highest PCE of 17.29%, and showing excellent stability by maintaining over 80% of the original PCE without any encapsulation after 1000-hour storage in ambient air.