Enhanced efficiency and stability of electron transport layer in perovskite tandem solar cells: Challenges and future perspectives

Perovskite solar cells (PSCs) have attracted extensive research interest in energy harvesting systems for their superior performance due to high absorption coefficients, long electron-hole diffusion length and ambipolar charge transport. The rapid progress achieved in conversion efficiency and charge transfer stabilities of PSCs is promising to meet future energy demands. Nevertheless, the long-term stability of the absorber and the electron transport layers (ETL) of PSCs is a significant challenge for commercialization. This review focuses on PSCs' stability, efficiency, interface engineering, and durability, particularly emphasising their ZnO-based ETL. Recent progress and challenges in enhancing the stability against moisture-induced, thermal-induced, and UV light-induced degradation have also been discussed critically. The review presents the enhancement in efficiency and stability via tandem configurations and highlights existing challenges and future perspectives.