De-doping engineering for efficient and heat-stable perovskite solar cells

Abstract

In conventional n-i-p perovskite solar cells, unsolved issues persist, particularly concerning notorious performance degradation under prolonged heat exposure at 85°C. By reducing the concentration of 4-tert-butylpyridine (tBP) and lithium bis(trifluoromethanesulfonyl)imide and adjusting their molar ratio to one, we achieved a dramatic increase in the heat stability of the PSC while boosting its power conversion efficiency (PCE). The formation of a 1:1 Li⁺-tBP complex was crucial for preventing free tBP molecules in the hole-transporting layer (HTL), suppressing the de-doping of the p-type HTL by tBP and the release of tBP vapor under heat stress. Consequently, the PSCs accomplished a PCE of 26.18% (certified 26.00%) while demonstrating remarkable resilience to heat exposure at 85°C due to the raised glass transition temperature of the HTL. Furthermore, a perovskite solar mini-module with an aperture area of 25 cm² achieved a PCE of 23.29%, highlighting their potential for commercial PSC deployment.