Lattice Manipulation with Di-Tertiary Ammonium Spacer in Bismuth Bromide Perovskite Directs Efficient Charge...

Bismuth halide hybrid perovskites have emerged as promising alternatives to their lead halide homologs because of high chemical stability, low toxicity, and structural diversity. However, their advancements in optoelectronic field are plagued with poor charge transport, due to considerable microstrain triggered by bulky spacer. Herein, the di-tertiary ammonium spacer (N,N,N',N'-tetramethyl-1,4-butanediammonium, TMBD) is explored to direct stable 1D bismuth bromide lattice structure with relaxed microstrain. Compared to the primary pentamethylenediamine (PD)²⁺, the (TMBD)²⁺ adopting alternating alignment enables a unique H-bonds mode to distort the configuration of inorganic layers to form corner-sharing [BiBr₅] near-regular chains with narrower bandgap, lower exciton binding energy, and reduced carrier-lattice interactions, thereby facilitating charge-carrier transport. Moreover, the (TMBD)²⁺ spacers largely suppress ion migration in perovskite lattice, as substantiated by the experimental and theoretical investigations. Consequently, (TMBD)BiBr₅ single crystal photodetector delivers a 185-fold increase in current on/off ratio with respect to (PD)BiBr₅ under white light irradiation, considerable responsivity (≈82.97 mA W^-1), detectivity (≈8.06 ×10¹¹ Jones) under weak light (0.02 mW cm^-2) irradiation, in the top rank of the reported hybrid bismuth halide perovskites. This finding offers novel design criterion for high-performance lead-free perovskites.