Mixed Dimethylammonium/Methylammonium Lead Halide Perovskite Single Crystals for Improved Structural Stability and Enhanced Photodetection.

We utilize the solvent acidolysis crystallization technique to grow mixed dimethylammonium/methylammonium lead tribromide (DMA/MAPbBr3 ) crystals reaching the highest dimethylammonium incorporation of 44% while maintaining the 3D cubic perovskite phase. These mixed perovskite crystals show suppression of the orthorhombic phase and a lower tetragonal to cubic phase transition temperature compared to MAPbBr3 . We observe distinct behavior in the temperature-dependent photoluminescence properties of MAPbBr3 and mixed DMA/MAPbBr3 crystals due to the different organic cation dynamics governing the phase transition(s). Furthermore, we fabricate lateral photodetectors which show that, at room temperature, the mixed crystals possess higher detectivity compared to MAPbBr3 crystals caused by structural compression and reduced surface trap density. Remarkably, the mixed crystal devices exhibit large enhancement in their detectivity below the phase transition temperature (at 200K), while the MAPbBr3 devices demonstrate insignificant changes. The higher detectivity makes our devices attractive for visible light communication and for space applications. Our results highlight the importance of the synthetic technique for the halide perovskites compositional engineering that governs their structural and optoelectronic properties. This article is protected by copyright. All rights reserved.