Energetics Modulation for Efficient and Stable n-i-p Perovskite Solar Cells

Abstract

The operational stability of n-i-p perovskite solar cells (PSCs) under heat, air and humidity have notably improved over recent years. Yet, performance degradation under light and voltage bias remains a concern for their commercial deployment. One of the main causes of such degradation relates to mobile ions in the perovskite film, which can trigger ion migration and self-accelerating chemical degradation. Here, we propose an energetics modulation strategy by developing the electron-withdrawing Pyridinecarboxaldehyde oxime (PO) ligand for FAPbI3-based perovskites. The introduction of PO ligands increases the ionization potential of the perovskite, inhibiting the generation of mobile ions during the crystallization process and subsequent device operation. Furthermore, this additive promotes the reaction between PbI2 and organic salts, which can help to regulate the energy level of perovskite and facilitate charge transport to the contact stacks. As a result, the optimized n-i-p PSCs exhibit a high efficiency of 26.13% and maintain over 88% of their initial efficiency after 1,000 h maximum power point (MPP) tracking test under one sun illumination. This work underlines the importance of energetics modulation for inhibiting intrinsic perovskite degradation that cannot be achieved by mere device encapsulation.