Lead-free organic–inorganic tin halide perovskites for photovoltaic applications

TLDR

Organic–inorganic lead halide perovskite solar cells already reach over 17 % efficiency, but lead toxicity is a concern; tin is a potential substitute, yet tin(II) instability hampers performance. The study reports the first fully lead‑free CH₃NH₃SnI₃ perovskite solar cell on a mesoporous TiO₂ scaffold, achieving over 6 % efficiency under 1 sun illumination. The device delivers an open‑circuit voltage exceeding 0.88 V from a 1.23 eV band‑gap material.

Abstract

Already exhibiting solar to electrical power conversion efficiencies of over 17%, organic–inorganic lead halide perovskite solar cells are one of the most promising emerging contenders in the drive to provide a cheap and clean source of energy. One concern however, is the potential toxicology issue of lead, a key component in the archetypical material. The most likely substitute is tin, which like lead, is also a group 14 metal. While organic–inorganic tin halide perovskites have shown good semiconducting behaviour, the instability of tin in its 2+ oxidation state has thus far proved to be an overwhelming challenge. Here, we report the first completely lead-free, CH3NH3SnI3 perovskite solar cell processed on a mesoporous TiO2 scaffold, reaching efficiencies of over 6% under 1 sun illumination. Remarkably, we achieve open circuit voltages over 0.88 V from a material which has a 1.23 eV band gap.