Investigation of shift current along off-polar axis in organic-inorganic perovskites

Shift current has attracted much attention for photovoltaic applications because it is energetically less dissipative (npj Comput. Mater., 2, 16026, 2016). Shift current is generated by the shift of electron clouds in real space upon photoexcitation, and it is expected to flow in any noncentrosymmetic materials belonging to piezoelectric point groups. However, the correlation between shift current and polarization is still under debate. Recent experimental results showed that the shift current of organic-inorganic hybrid perovskites is generated dominantly along the polarization axis (Chem. Mater., 34, 10, 4428, 2022). In this work, we investigate the shift current of organic-inorganic perovskites flowing along off-polar axis. We synthesized ((R)-(-)-1-cyclohexylethylamine)₈Pb₃I₁₄ single crystals belonging to a chiral-polar space group of P2₁. We measured the zero-bias photocurrent flowing along the direction perpendicular to the polarization axis. It was found that the photocurrent generation along the off-polar axis can be well explained by the shift current theory and cannot be explained by the classical bulk photovoltaic effect where internal electric fields make a great contribution to photocurrent generation. In future work, the contribution of exciton and interband transitions will be elucidated by spectroscopic measurement.