Moisture-dependent room-temperature perovskite crystallization in vacuum flash-assisted solution processed intermediate phase films

Abstract

We propose a straightforward intermediate-phase strategy to facilitate large-area crystallization of perovskite under room-temperature: preparing intermediate phase film with vacuum flash-assisted solution processing (VASP) method and performing controlled moisture-exposure subsequently. Moisture molecules penetrate into the whole intermediate film, remove residual solvent molecules, and trigger room-temperature crystallization of perovskite in a wide humidity range (25–80% RH), while negligible hydroxyl species are observed in the intermediate phase and resultant perovskite films. Without antisolvent, thermal-annealing and additive, high-humidity (80% RH) exposure of intermediate-phase film under room-temperature results in crystalline perovskite with a 8× increase in grain size and a 6× increase in photoluminescence lifetime, which is attributed to the homogenous and stable intermediate phase prepared by VASP and the synergistic effect of H 2 O and residual solvent molecules. Without antisolvent, thermal-annealing and additive, high-humidity (80% RH) exposure of intermediate-phase precursor film under room-temperature results in crystalline perovskite with a 8× increase in grain size and a 6× increase in photoluminescence lifetime. • The intermediate phase strategy applies in the wide range of 25–80% RH humidity. • Moisture exposure under room-temperature induces identical chemical transition. • Negligible hydroxyl species are observed in perovskite and its intermediate. • 80% RH exposure leads micron-size grains and microsecond fluorescence lifetime.