High‐Temperature Ionic Epitaxy of Halide Perovskite Thin Film and the Hidden Carrier Dynamics

High‐temperature vapor phase epitaxy (VPE) has been proved ubiquitously powerful in enabling high‐performance electro‐optic devices in III–V semiconductor field. A typical example is the successful growth of p‐type GaN by VPE for blue light‐emitting diodes. VPE excels as it controls film defects such as point/interface defects and grain boundary, thanks to its high‐temperature processing condition and controllable deposition rate. For the first time, single‐crystalline high‐temperature VPE halide perovskite thin film has been demonstrated—a unique platform on unveiling previously uncovered carrier dynamics in inorganic halide perovskites. Toward wafer‐scale epitaxial and grain boundary‐free film is grown with alkali halides as substrates. It is shown the metal alkali halides could be used as universal substrates for VPE growth of perovskite due to their similar material chemistry and lattice constant. With VPE, hot photoluminescence and nanosecond photo‐Dember effect are revealed in inorganic halide perovskite. These two phenomena suggest that inorganic halide perovskite could be as compelling as its organic–inorganic counterpart regarding optoelectronic properties and help explain the long carrier lifetime in halide perovskite. The findings suggest a new avenue on developing high‐quality large‐scale single‐crystalline halide perovskite films requiring precise control of defects and morphology.