The dual role of borohydride salts in enhancing perovskite solar cell performance and stability

Abstract

A key problem for materials that form lead-based perovskite is the part of organic iodide that is oxidized and forms molecular I₂, which negatively affects the efficiency and stability of the solar cell. Herein, we explored adding special compounds, two borohydride salts, potassium borohydride (KBH₄) and sodium borohydride (NaBH₄), into the perovskite precursor solution. These borohydride salts help prevent the oxidation process by acting as reducing agents, preventing the defects caused by I₂ by converting it back to I⁻. Also, I₃⁻ is generated from I₂ and I⁻, which has a strong binding affinity to FA⁺, leading to deprotonation and decomposition of the perovskite. Borohydride salts can prevent this degradation and help stabilize the precursor solution. Furthermore, borohydride salts have a second role, enhancing film crystallinity and defect passivation and increasing humidity resistance, which improves overall stability and device performance. As a result, a promising efficiency of 20% is achieved, exhibiting long-term stability.