Highly stable and efficient all-inorganic lead-free perovskite solar cells with native-oxide passivation

TLDR

Lead‑free halide perovskite solar cells are urgently needed, yet they typically exhibit low efficiency and poor stability due to inadequate photovoltaic properties and chemical stability. This study proposes native‑oxide passivation as an alternative strategy to enhance the efficiency and stability of lead‑free perovskite solar cells. The authors achieve this by forming a full‑coverage, stable native‑oxide layer that encapsulates and passivates the perovskite surfaces. The resulting CsSn₀.₅Ge₀.₅I₃‑based PSCs reach a peak efficiency of 7.11 % and retain over 90 % of their performance after 500 h of continuous one‑sun operation in N₂.

Abstract

There has been an urgent need to eliminate toxic lead from the prevailing halide perovskite solar cells (PSCs), but the current lead-free PSCs are still plagued with the critical issues of low efficiency and poor stability. This is primarily due to their inadequate photovoltaic properties and chemical stability. Herein we demonstrate the use of the lead-free, all-inorganic cesium tin-germanium triiodide (CsSn0.5Ge0.5I3) solid-solution perovskite as the light absorber in PSCs, delivering promising efficiency of up to 7.11%. More importantly, these PSCs show very high stability, with less than 10% decay in efficiency after 500 h of continuous operation in N2 atmosphere under one-sun illumination. The key to this striking performance of these PSCs is the formation of a full-coverage, stable native-oxide layer, which fully encapsulates and passivates the perovskite surfaces. The native-oxide passivation approach reported here represents an alternate avenue for boosting the efficiency and stability of lead-free PSCs. Replacing the toxic lead in the state-of-the-art halide perovskite solar cells is highly desired but the device performance and stability are usually compromised. Here Chen et al. develop inorganic cesium tin and germanium mixed-cation perovskites that show high operational stability and efficiency over 7%.