Enhanced Photoluminescence and Solar Cell Performance <i>via</i> Lewis Base Passivation of Organic–Inorganic Lead Halide Perovskites

TLDR

Organic–inorganic metal halide perovskites have emerged as a leading low‑cost photovoltaic absorber, achieving up to 17.9 % efficiency despite the high defect density typical of solution‑processed semiconductors. The study aims to reduce nonradiative recombination in CH₃NH₃PbI₃–xClₓ perovskites by surface treatment with Lewis bases thiophene and pyridine. Treating the crystal surfaces with thiophene or pyridine passivates under‑coordinated Pb atoms, extending photoluminescence lifetimes to nearly 2 µs and suppressing electron–hole recombination. This passivation raises power‑conversion efficiencies from 13 % in untreated cells to 15.3 % and 16.5 % for thiophene‑ and pyridine‑treated devices, respectively.

Abstract

Organic–inorganic metal halide perovskites have recently emerged as a top contender to be used as an absorber material in highly efficient, low-cost photovoltaic devices. Solution-processed semiconductors tend to have a high density of defect states and exhibit a large degree of electronic disorder. Perovskites appear to go against this trend, and despite relatively little knowledge of the impact of electronic defects, certified solar-to-electrical power conversion efficiencies of up to 17.9% have been achieved. Here, through treatment of the crystal surfaces with the Lewis bases thiophene and pyridine, we demonstrate significantly reduced nonradiative electron–hole recombination within the CH3NH3PbI3–xClx perovskite, achieving photoluminescence lifetimes which are enhanced by nearly an order of magnitude, up to 2 μs. We propose that this is due to the electronic passivation of under-coordinated Pb atoms within the crystal. Through this method of Lewis base passivation, we achieve power conversion efficiencies for solution-processed planar heterojunction solar cells enhanced from 13% for the untreated solar cells to 15.3% and 16.5% for the thiophene and pyridine-treated solar cells, respectively.