The research field on perovskite solar cells (PSCs) is seeing frequent record breaking in the power conversion efficiency (PCE). However, organic-inorganic hybrid halide perovskites and organic additives in common hole-transport materials (HTMs) exhibit poor stability against moisture and heat. Here we report the successful fabrication of all-inorganic PSCs without any labile or expensive organic components. The entire fabrication process can be operated in ambient environment without humidity control (e.g., a glovebox). Even without encapsulation, the all-inorganic PSCs present no performance degradation in humid air (90-95% relative humidity, 25 °C) for over 3 months (2640 h) and can endure extreme temperatures (100 and -22 °C). Moreover, by elimination of expensive HTMs and noble-metal electrodes, the cost was significantly reduced. The highest PCE of the first-generation all-inorganic PSCs reached 6.7%. This study opens the door for next-generation PSCs with long-term stability under harsh conditions, making practical application of PSCs a real possibility.

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An efficient method to synthesize well-crystallized inorganic cesium lead halide perovskites (CsPbX, X = I or Br) with high yield and high reproducibility was proposed. Notably, the as-prepared CsPbI in the yellow orthorhombic phase (y-CsPbI) can be easily converted to the black cubic perovskite phase CsPbI (b-CsPbI) after thermal annealing. Furthermore, two-terminal photodetectors and all-inorganic perovskite solar cells based on b-CsPbI were fabricated, exhibiting high performances.