As rapid progress has been achieved in emerging thin film solar cell technology, organic–inorganic hybrid perovskite solar cells (PVSCs) have aroused many concerns with several desired properties for photovoltaic applications, including large absorption coefficients, excellent carrier mobility, long charge carrier diffusion lengths, low‐cost, and unbelievable progress. Power conversion efficiencies increased from 3.8% in 2009 up to the current world record of 22.1%. However, poor long‐term stability of PVSCs limits the future commercial application. Here, the degradation mechanisms for unstable perovskite materials and their corresponding solar cells are discussed. The strategies for enhancing the stability of perovskite materials and PVSCs are also summarized. This review is expected to provide helpful insights for further enhancing the stability of perovskite materials and PVSCs in this exciting field.

Fullerene end-capped polyethylene glycol (C60-PEG) was introduced via an antisolvent method to fabricate the perovskite films. C60-PEG could enlarge the perovskite crystal size and passivate the defects of perovskite films, facilitating the carrier transport and hindering the carrier recombination. In consequence, the superior optoelectronic properties were attained with an improved power conversion efficiency of 17.71% for the perovskite device with C60-PEG treatment. Meanwhile, amphiphilic C60-PEG enhanced the resistance of perovskite films to moisture. After 40 days, the C60-PEG-based devices without encapsulation remained 93 and 86% of the original power conversion efficiency value under nitrogen and ambient conditions (25 °C temperature, 60% humidity), respectively.

Aminoguanidine hydrochloride passivated Sn-perovskite with a power conversion efficiency of 7.3%.

Perovskites with grain size comparable to film thickness are intensively pursued for high-efficiency solar cells. Geometrically, large grains with high crystallinity tend to form polyhedral shapes that have difficulty forming compact and smooth films. When quasi-two-dimensional RP perovskite films adopt a downward growth mode, defective contacts tend to form at their bottom interfaces with many nanocavities. This is attributed to the angular growing fronts of RP perovskite grains adopting [111] (or/and [101]) growth directions. Self-generated methylamine gas, by a replacement reaction in solution, is introduced to in situ heal these irregular nanocavities that are deeply buried in perovskite films during crystallization processes. The amount of self-generated methylamine gas should be adequately controlled to avoid the homogeneous nucleation of perovskites from a liquid perovskite-amine intermediate phase, which is a key to avoid ruining the grain size and film composition. This in situ healing strategy offers significantly enhanced charge collection efficiency and device working stability.

Polycrystalline perovskite films generally have high-density defects due to the numerous crystal nucleus and randomly oriented fine grains in the film formation. These defects are commonly regarded as the source...