Conjugated Polyelectrolyte-Passivated Stable Perovskite Solar Cells for Efficiency beyond 20%

Developing large-scale perovskite solar cells requires high-quality defect-free perovskite films with improved surface coverage. One of the most convenient ways to achieve this is through the incorporation of appropriate passivation molecules in the perovskite films. Herein, the effect of a novel conjugated polyelectrolyte, PHIA, is investigated for perovskite passivation by the comprehensive analysis of perovskite films and devices. The PHIA polymer significantly diminishes the trap states in perovskite films, and the passivated device permits lesser recombination, very low accumulation of charges at the interface, and lowers the traps which facilitated superior charge transport. As a result, a high power conversion efficiency of 20.17% has been achieved for the PHIA-modified device. Additionally, this passivation approach effectively enhanced the long-term device stability by improving the hydrophobicity of the perovskite layer. Furthermore, a large-area device (2 cm2) has also been fabricated to demonstrate the expediency of this approach for future commercialization.