Post-Treatment of Metal Halide Perovskites: From Morphology Control, Defect Passivation to Band Alignment and Construction of Heterostructures

Metal halide perovskite solar cells (PSCs) have witnessed a swift increase in power conversion efficiency in the past decade, emerging as one of the most promising next-generation photovoltaic technologies for commercialization and low-carbon energy generation. Through significant efforts in optimizing the processing techniques, high-quality perovskite thin films can now be prepared with polycrystalline morphologies consisting of monolayer grains. Nevertheless, defects and microstructural disorders still form at the surface/heterointerface and in the bulk of the films. Post-treatment of the as-crystallized films has been intensively investigated for passivating these defects, being proved effective for improving the device performance. In this review, the versatile strategies for post-treating the surface of perovskite thin films toward morphology control, defect passivation, and band alignment are discussed. The tailored surface properties are correlated to charge dynamics at interfaces and photovoltaic performance of PSCs. Since the perovskite heterostructures prepared by simple post-treatments may suffer from degradation at high temperatures, the recent advances in preparing phase-pure and stable perovskite heterostructures are also discussed. Finally, a perspective elaborating future opportunities for further enhancing the efficiency and stability of PSCs is provided.