Transition from Dion-Jacobson hybrid layered double perovskites to 1D perovskites for ultraviolet to visible photodetection

Abstract

New perovskite phases having diverse optoelectronic properties are the need of the hour. We present five variations of R₂AgM(iii)X₈, where R = NH₃C₄H₈NH₃ (4N4) or NH₃C₆H₁₂NH₃ (6N6); M(iii) = Bi³⁺ or Sb³⁺; and X = Br^- or I^-, by tuning the composition of (4N4)₂AgBiBr₈, a structurally rich hybrid layered double perovskite (HLDP). (4N4)₂AgBiBr₈, (4N4)₂AgSbBr₈, and (6N6)₂AgBiBr₈ crystallize as Dion-Jacobson (DJ) HLDPs, whereas 1D (6N6)SbBr₅, (4N4)-BiI and (4N4)-SbI have trans-connected chains by corner-shared octahedra. Ag⁺ stays out of the 1D lattice either when SbBr₆^3- distortion is high or if Ag⁺ needs to octahedrally coordinate with I^-. Band structure calculations show a direct bandgap for all the bromide phases except (6N6)₂AgBiBr₈. (4N4)₂AgBiBr₈ with lower octahedral tilt shows a maximum UV responsivity of 18.8 ± 0.2 A W^-1 and external quantum efficiency (EQE) of 6360 ± 58%, at 2.5 V. When self-powered (0 V), (4N4)-SbI has the best responsivity of 11.7 ± 0.2 mA W^-1 under 485 nm visible light, with fast photoresponse ≤100 ms.

Fig. 1. Crystal structures along the a- and c-axes, with the bond lengths and angles for (a) (4N4)₂AgBiBr₈ (reproduced), (b) (4N4)₂AgSbBr₈, (c) (6N6)₂AgBiBr₈, and (d) (6N6)SbBr₅. All bond lengths are in Å.

Fig. 2. Absorption and PL spectra of (a) (4N4)₂AgBiBr₈ and (4N4)₂AgSbBr₈, (b) (6N6)₂AgBiBr₈ and (6N6)SbBr₅, and (c) (4N4)–BiI, and (4N4)–SbI.

Fig. 3. Electronic band structures for (a) (4N4)₂AgBiBr₈, (b) (4N4)₂AgSbBr₈, (c) (6N6)₂AgBiBr₈ and (d) (6N6)SbBr₅. The calculations were performed with SOC and the green lines represent the Fermi energy level.

Fig. 4. Potential-biased photodetector performance. (a) Schematic of the photodetector device. Responsivity–potential plots under 1 sun visible light and 370 nm UV light for (b and c) (4N4)₂AgBiBr₈, and (d and e) (4N4)₂AgSbBr₈. (f) Bar plots of the highest responsivity and EQE under visible and UV radiation for (4N4)₂AgBiBr₈ and (4N4)₂AgSbBr₈. Responsivity–potential plots under 1 sun visible light and 370 nm UV light for (g) (6N6)₂AgBiBr₈ and (h) (6N6)SbBr₅.

Fig. 5. Self-powered photodetector performance. Chronoamperometry plots at different light intensities, for (4N4)₂AgBiBr₈ under (a) 370 nm UV and (b) 1 sun visible light, (4N4)₂AgSbBr₈ under (c) 370 nm UV and (d) 1 sun visible light, (e) (6N6)₂AgBiBr₈ and (f) (6N6)SbBr₅, under UV light, and (g) (4N4)–BiI and (h) (4N4)–SbI in the presence of visible light.