Enhanced Quasi-Fermi Level Splitting of Perovskite Solar Cells by Universal Dual-Functional Polymer.

Perovskite solar cells have attracted extensive attention due to their higher power conversion efficiency and simple fabrication process. However, the open-circuit voltage (V OC ) loss remains a significant impediment to enhance device performance. Here, we demonstrate a facile strategy to boost the V OC to 95.5% of the Shockley-Queisser (S-Q) limit through the introduction of a universal multifunctional polymer additive. This additive effectively passivates the cation and anion defects simultaneously, thereby leading to the transformation from the strong n-type to weak n-type of perovskite films. Benefitting from the energy level alignment and the suppression of bulk non-radiative recombination, the quasi-Fermi level splitting (QFLS) is enhanced.  Consequently, the champion devices with 1.59 eV-based perovskite reached a highest V OC value of 1.24 V and a power conversion efficiency (PCE) of 23.86%. Furthermore, this strategy boosts the V OC by at least 0.07 V across five different perovskite systems and a PCE of 25.04% was achieved for 1.57 eV-based PSCs, the corresponding module (14 cm 2 ) also obtained a high PCE of 21.95%. This work provides an effective and universal strategy to promote the V OC approach to the detailed balance theoretical limit. This article is protected by copyright. All rights reserved.