Precise Emission Bandgap Engineering in Hybrid Perovskite: An ITC Approach

Hybrid lead halide perovskites are promising next-generation materials for optoelectronic applications, including LEDs, lasers, photodetectors, and solar cells. This study focuses on precise photophysical characterization and synthesis optimization to achieve controlled emission band tuning. Using the inverse temperature crystallization (ITC) method, we addressed key synthesis challenges such as solvent-specific precursor solubility limitations. To improve PbCl₂ solubility in DMF, we prepared MACl:PbCl₂ solutions in DMSO at 140°C then diluted with DMF. Similarly, MAPbI₃ in GBL exhibited unique solvothermal behavior, favoring luminescent crystallization at 110°C. A systematic shift in the transmittance edge was observed, ranging from 780 nm for MAPbI₃ to 549 nm for MAPbBr₃ and 421 nm for MAPbCl₃. Red-shifting from bright green (MAPbBr₃) to blood-red (MAPbBr₁.₅I₁.₅, 650 nm) was achieved, with intermediate Br:I compositions yielding yellow (590 nm) and orange (605 nm) emissions. Similarly, varying Br:Cl ratios resulted in tunable blue emissions from deep blue (441 nm) to cyanine (490 nm). A major challenge in hybrid perovskite photophysical characterization is phase segregation under UV excitation, leading to dual-color emission. To mitigate this, we employed controlled excitation light intensity, low-temperature measurements, two-photon absorption, and pulsed laser excitation. A scanning-mode measurement approach further enhanced emission accuracy. This study advances hybrid perovskite research by refining emission band fine-tuning methodologies, providing critical insights for the development of high-performance optoelectronic devices.