LAUSR

Facet‐orientated double perovskite (DP) microcrystals (MCs) are of particular interest in optoelectronics due to the special symmetry and homogeneous interfaces, which extend the carrier lifetime and enhance the mobility to realize robust device performance. Here, a simple hot‐spin casting method is developed to instantaneously synthesize the highly crystalline lead‐free halide DP Cs2AgBiBr6 MCs with facet‐orientation. The low temperature (130 °C) hot‐spin casting synthesis of DP MCs instigates growth only along the highly packed (111) plane attributed to heterogeneous nucleation. The Cs2AgBiBr6 DP MCs demonstrate reduced lattice parameters with enhanced light absorbance resulting in decreased bandgap (ΔEg ≈ 0.23 eV). The facet‐oriented DP MCs exhibit the enhancement in photoluminescence and carrier lifetime compared to the nanocrystalline thin‐film. Moreover, the DP MCs are successfully transferred on the desired substrate using micro‐imprint lithography keeping its original orientation intact. The DP Cs2AgBiBr6 MCs‐based photodetectors manifest broader spectral response, high detectivity (1.72 × 1011 Jones) and improved external quantum efficiency (EQE, 451%). The freestanding and facet orientated DP MCs synthesis is easily extendable to other types of halide perovskites and has the potential to fabricate high‐performance optoelectronic devices.