RESUMEN
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.
RESUMEN
Two-dimensional (2D) Dion-Jacobson (DJ) perovskites are drawing significant attention in optoelectronic fields because of their enhanced out-of-plane electron coupling and improved structure stability. However, the structural effects of organic cations on the in-plane charge transport properties of 2D DJ lead bromide perovskites have remained less explored. Herein, we adopt asymmetric 3-(dimethylamino)-1-propylammonium (DMPD) and symmetric butane-1,4-diammonium (BDA) to systematically investigate the influence of organic cations on the structural, optical, and in-plane charge transport properties of 2D lead bromide perovskites. The large penetration depth of DMPD2+ induces a decreased perovskite layer distortion and a lower bandgap in DMPDPbBr4, compared with that of BDAPbBr4. Moreover, DMPDPbBr4 is shown to possess a low exciton binding energy, a low defect density, and a low ion migration activation energy, thereby yielding a more efficient in-plane charge collection efficiency than BDAPbBr4. Density functional theory calculations suggest that the improved in-plane charge transport can be traced to the enlarged antibonding coupling between Pb-6s and Br-4p orbitals that enables a high band dispersion and a low carrier effective mass in the in-plane direction of DMPDPbBr4. Finally, the planar Ag/DMPDPbBr4/Ag photodetector delivers a satisfying detectivity of 1.73 × 1012 Jones under an incident power intensity of 0.16 mW cm-2 and a high on/off ratio of 5.3 × 103. The above findings offer novel insight for the design of 2D DJ lead bromide perovskites for optoelectronic devices.