Interfacial Engineering for High-Efficiency Nanorod Array-Structured Perovskite Solar Cells.

TiO2 nanorod (NR) array for perovskite solar cells (PSCs) has attained great importance due to its superb power conversion efficiency (PCE) compared to that of the traditional mesoporous TiO2 film. A TiO2 compact layer for the growth of TiO2 NR array via spin-coating cannot meet the requirements for efficient NR-based PSCs. Herein, we have developed and demonstrated the insertion of a bifunctional extrathin TiO2 interlayer (5 nm) by atomic layer deposition (ALD) at the interface of the fluorine-doped tin oxide (FTO)/TiO2 compact layer to achieve alleviated electron exchange and a reduced energetic barrier. Thus, an accelerated extraction of electrons from TiO2 NR arrays via the compact layer and their transfer to the FTO substrate can improve the PSC efficiency. The thickness of the spin-coated TiO2 compact layer on the ALD-deposited TiO2 layer is spontaneously optimized. Finally, an outstanding efficiency of 20.28% has been achieved from a champion PSC with negligible hysteresis and high reliability. To the best of our knowledge, this is the first study demonstrating the superiority of TiO2-NR-based PSCs withstanding the dry heat and thermal cycling tests. The results are of great importance for the preparation of efficient and durable PSCs for real-world applications.