Given that thermal stability is of considerable importance in the field of photovoltaics, inorganic perovskites have attracted numerous attempts to overcome instability caused by volatile cations in organic–inorganic hybrid perovskites. As always, crystallization optimization is a paramount strategy to enhance the performance of inorganic perovskite‐based solar cells. Recently, nanoconfined crystallization is regarded as a novel and effective strategy due to the absence of chemical reactions. Herein, 1D ordered mesoporous silica is introduced into inorganic perovskite precursors to facilely induce the nanoconfined crystallization. Both theoretical and experimental analyses verify that the nanoconfined crystallization is successfully triggered by the ordered mesoporous silica, fostering the formation of 1D perovskite monocrystal. In addition, the crystallization and morphology of inorganic perovskite are effectively facilitated. As a result, the nonradiative recombination is suppressed along with the distinctly reduced trap‐state density and remarkably enhanced charge transport in perovskite. Finally, the power conversion efficiencies of CsPbIBr2‐ and CsPbI3‐based solar cells are boosted from 8.67% to 10.04% and from 14.10% to 14.69%, respectively. Meanwhile, stability tests of solar cells also show enhancement using the nanoconfined crystallization. This work provides a facile, effective, and flexible crystallization modulating strategy for fabricating efficient and stable inorganic perovskite solar cells.
