Interface engineering via phthalocyanine decoration of perovskite solar cells with high efficiency and stability

Abstract

Organic semiconductor additives offer a promising strategy to partially eliminate defects within polycrystalline perovskite films. However, these additives are often photochemically unstable. Attempts to improve the delicate performance of perovskite solar cells (PSCs) by these additives are unimpressive. Here, we use an organic small-molecule semiconductor with unique photochemical stability, 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine (Pc), to decorate perovskite/hole transfer layer interface. Pc molecules are observed to be located in the perovskite shallow layer and probably at perovskite grain boundaries. PSCs with moderate Pc decoration show mean and best power conversion efficiencies (PCEs) of 19.3% and 19.8%, respectively, compared to 17.5% and 18.5% for the control. The PCE decay of the best PSC with moderate Pc is less than 10% of the initial PCE, and almost 30% for the best control under 500 h continuous illumination and ambient atmosphere (~30% humidity). The photovoltaic performance enhancement induced by Pc decoration is ascribed to the decreased perovskite hole trap state density (from 2.07 × 1016 to 1.11 × 1016 cm−3), the increased perovskite hole mobility (from 7.73 × 10−3 to 1.22 × 10−2 cm2V−1s−1), improved charge carrier transfer and extraction, and partially sealed channels to impede moisture diffusion.