Synthesis and Exciton Dynamics of a One-Dimensional Organic Copper Halide Perovskite

Low-dimensional copper halides have recently received increasing attention, owing to their non-toxicity, low-cost, and efficient broadband emission with large Stokes shift. Herein, we report a novel one-dimensional organic copper halide PEACuI2 (PEA = C6H5CH2CH2NH3+), which exhibits broad green emission originating from self-trapped excitons (STEs) with a peak of 525 nm and large Stokes shifts of 215 nm. The dynamics and multi-body interactions of STEs were investigated using femtosecond transient absorption (fs TA) spectroscopy at different pump intensities. Interestingly, under high STE density, we observed the absorption signals of self-trapped biexcitons (STBs) formed by binding two STEs in the fs TA spectra. The hot STBs undergo cooling process with a rate constant of 3.57 ps, yielding relaxed STBs. Furthermore, a trap-associated recombination of STBs with a time constant of 64.98 ps is unveiled. Our results offer direct evidence of the occurrence of STBs and provide new insights into the many body interactions of STEs.