Ionic and electronic current under photo-illumination in a chiral organic metal halide hybrid*

Organic halide perovskites have attracted much interest due to their favorable properties in optoelectronics. We recently demonstrated that single crystals of the 1D organic metal halide (R-α-MBA)PbI₃ exhibit excellent chemical and electronic stability, which enabled highly reproducible time-dependent electrical measurements^[1]. The four-terminal I-V and V-t measurements yielded real-time ionic and electronic currents and revealed single exponential intrinsic ion migration dynamics of distinct time constants as short as 3 s. Here, we report the effects of photo illumination of different wavelengths and intensities on the ion migration dynamics. The reproducible I-V and V-t results evidence reversible effects of photo illumination: Both the magnitude of the ionic current and the time constant of the exponential ion migration dynamic increase with the illumination time and intensity, which indicate an increase of mobile ion density and decrease of their mobility with light illumination. The stability of the materials and reversibility of the photo-activated and field-assisted ion migration suggests that the shift current may be measured in the chiral crystals using scanning photo-current microscopy. A comparison of the shift current in crystals of opposite handedness (R- vs S-) may produce new insight into its microscopic origin.

[1] Zhenqi Hua, et al., ACS Energy Lett. 2022, 7, XXX, 3753–3760, doi.org/10.1021/acsenergylett.2c01710