A nanofibrillar conjugated polymer film as an interface layer for high-performance CsPbIBr2 solar cells with efficiency exceeding 11%

Abstract

The perovskite/hole-transporting layer interface plays a crucial role in the performance of perovskite solar cells. Herein, a conjugated polymer (CP) is employed as an interface layer in CsPbIBr₂ solar cells. On top of the CsPbIBr₂ layer, the CP self-assembled into a nanofibrillar film which shows multiple effects: optimization of the energy level alignment, enhancement of the hole extraction, passivation of the perovskite layer and reduction of the defect density. As a result, the power conversion efficiency of the corresponding CsPbIBr₂/CP device is improved to 11.05%, with a V_OC of 1.19 V, a J_SC of 12.69 mA cm⁻², and a FF of 73.31%. Moreover, the device efficiency retains about 91% of its initial value for nearly 900 hours in air. This proposed CP-passivated interface strategy will open a new avenue for achieving high-performance inorganic perovskite solar cells.