Publication date: 17th February 2025
Mixed lead halide perovskites are widely recognized as one of the most promising materials for next generation solar cells, light-emitting diodes, and photodetectors. They display great light harvesting properties, tunability, ease of fabrication, low costs, and defect tolerance. However, their lack of stability under external stimuli, such as light illumination, has so far prevented large scale utilization in devices. One demonstration of this instability is the reversible halide segregation observed in mixed-halide perovskites. Upon illumination, these materials transition from a homogeneously mixed state to a multi-bandgap configuration, with iodide-rich and bromide-rich domains forming over seconds.
In this work, we monitor the dynamics of halide segregation in MAPbBr₁.₅I₁.₅ under femtosecond pulsed laser illumination with tunable parameters, such as average power, repetition rate (rep-rate), pulse fluence, and device temperature. Our results reveal a strong dependence of the photoluminescence (PL) emission wavelength and intensity on the excitation rep-rate and power. Additionally, by varying the sample temperature between room temperature and 100 degrees Celsius, we are able to tune the emission wavelength further, and control the segregation and remixing rates. Notably, the output PL wavelength encodes a combination of input excitation parameters, effectively enabling a memory storage function within the material.
In conclusion, this study deepens our understanding of the interplay between photoinduced defect dynamics and halide segregation and opens up new opportunities to exploit their dynamic photophysical properties. By harnessing halide segregation as a controllable and reversible mechanism, we provide a pathway to innovate beyond conventional optoelectronic applications, turning a stability challenge into a functional advantage.
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