Reducing Agents for Improving the Stability of Sn‐based Perovskite Solar Cells

Abstract

Organic-inorganic hybrid perovskite solar cells (PSCs) have aroused tremendous research interest for their high efficiency, low cost and solution processability. However, the involvement of toxic lead in state-of-art perovskites hinders their market prospects. As an alternative, Sn-based perovskites exhibit similar semiconductor characteristics and can potentially achieve comparable photovoltaic performance in comparison with their lead-based counterparts. The main challenge of developing Sn-based PCSs lies in the intrinsic poor stability of Sn 2 + , which could be oxidized and converted to Sn 4 + . Notably, introduction of SnX 2 (X = Cl, Br, I) additive becomes indispensable in the fabrication process, which highlights the importance of incorporating a reducing agent to improve the device stability. Additionally, efforts are made to utilize other reducing agents with different functions for the further enhancement of device performance. Currently, Sn-based PSCs could attain a record efficiency over 10% with great stability. In this review, we present the recent progress on reducing agents for improving the stability of Sn-based PSCs, and we hope to shed light on the challenges and opportunities of this research field. 2 3 4 5 6 7 8

Tuning cesium–guanidinium in formamidinium tin triiodide perovskites with an ethylenediammonium additive for efficient and stable lead-free perovskite solar cells

“…14,24 Excess SnI 2 has been shown to be effective in preventing Sn 2+ oxidation by both compensating and suppressing Sn 2+ vacancies without having any adverse side effects on phase stability and phase segregation. 25,26 Previous research has argued that excess SnI 2 may even be more effective than SnF 2 as a reducing agent since SnF 2 is hard to dissociate in films because of its low solubility and stability. 27 To minimize SnF 2 assisted phase segregation, we use excess SnI 2 plus EDAI 2 to reduce Sn 2+ oxidation.…”

2D WSe2 Flakes for Synergistic Modulation of Grain Growth and Charge Transfer in Tin‐Based Perovskite Solar Cells

“…Thus reducing agents should be introduced to prohibit the oxidation of the perovskite films, [ 19–21 ] which in turn leads to a less conductive layer unfavorable for charge transfer on grain surfaces. [ 22–24 ]…”

Recent progress toward highly efficient tin‐based perovskite (ASnX3) solar cells

“…[ 139 ] Hydrazine is a convenient reductant because the by‐products are typically N 2 and H 2 O. [ 50,140 ] Nevertheless, highly toxic, flammable, the exact amount being hard to control and excess N 2 H 4 forces deeper reduction to Sn 0 , limit its further utilization.…”