Unique Perovskitizer N─Pb Bond Switching Induced Polar Photovoltaic Effect in Trilayered Hybrid Perovskite

Polar photovoltaic effect (PPE) has attracted great attention in regulating desired optoelectronic properties, which can be driven by order-disorder and displacive phase transitions. Bond-switching is also a feasible method to induce PPE, but such investigation is very rare. Lead-halide hybrid perovskite (LHHP) is an outstanding photodetection material; lead atoms possess rich coordination modes to provide possibilities to construct switchable bonds. Here, a unique perovskitizer N─Pb bond-switching is disclosed to induce polar photovoltage in the emerging LHHP, PA2MHy2Pb3Br10 (1, PA = n-propylamine, MHy = methylhydrazine). Interestingly, the perovskitizer MHy+ provides 2s2 lone pair while the Pb atom affords empty d orbitals, which coordinate with each other to generate a flexible N─Pb bond. Further, the introduction of N─Pb bonds results in a high distortion of the PbBr6 octahedron to form local polarity and further orientation to induce spontaneous polarization. More importantly, such a flexible N─Pb bond switching mechanism drives a notable PPE and controllable polarized photo-response, a polarization ratio up to 9.7 at the polar phase in striking contrast with the non-polar phase (1.03). The work provides the first demonstration of bond-switching to induce polar phase transition and polar photovoltage in the photoconductive hybrid perovskites for photoelectric applications.

Regulating Circularly Polarized Light Detection via Polar-Phase Transition in Alternating Chiral-Achiral Cations Intercalation-Type Hybrid Perovskites

Circularly polarized light (CPL) detection has wide applications in many fields, where the anisotropy factor (gIph ) is an important indicator to characterize the CPL detection performance. So far, many materials with high gIph have been reported, however, the exploration of the regulation of gIph is still in its infancy. Herein, two novel alternating chiral-achiral cations intercalation-type chiral hybrid perovskites (CHPs), named (R/S-1-phenylpropylamine)(propylamine)PbBr4 (1-R/S), exhibit above room-temperature (RT) polar-phase transition, which greatly regulates the gIph value. The gIph of 1-R is 0.04 in high-temperature phase chiral non-polar (P21 21 21 ) by applying 5 V bias, interestingly, with the temperature decrease, the gIph value in low-temperature phase chiral polar (P21 ) gradually increases (0.22@360K, 0.40@340K, 0.47@320K), and finally reaches a maximum of 0.5 at RT. Such value is not only the highest among 2D CHPs to date, but presents a 12.5-fold amplification compared with 0.04. Further, this rare phenomenon should be attributed to the built-in electric field induced by the polar photovoltaic effect, which sheds light on further obtaining CHPs with large gIph .