Constructing heterojunctions by surface sulfidation for efficient inverted perovskite solar cells

TLDR

Surface sulfidation of lead‑rich perovskite films creates a stable heterojunction for inverted solar cells. Pb–S bonds upshift the Fermi level, generate a back‑surface field, and enable inverted perovskite solar cells to reach >24 % PCE with 1.19 V Voc, low voltage loss, and retain over 90 % of initial efficiency after long‑term thermal and illumination aging.

Abstract

A stable perovskite heterojunction was constructed for inverted solar cells through surface sulfidation of lead (Pb)-rich perovskite films. The formed lead-sulfur (Pb-S) bonds upshifted the Fermi level at the perovskite interface and induced an extra back-surface field for electron extraction. The resulting inverted devices exhibited a power conversion efficiency (PCE) >24% with a high open-circuit voltage of 1.19 volts, corresponding to a low voltage loss of 0.36 volts. The strong Pb-S bonds could stabilize perovskite heterojunctions and strengthen underlying perovskite structures that have a similar crystal lattice. Devices with surface sulfidation retained more than 90% of the initial PCE after aging at 85°C for 2200 hours or operating at the maximum power point under continuous illumination for 1000 hours at 55° ± 5°C.