Abstract: Ferroelectric polymers, such as poly(vinylidene fluoride-trifluoroethylene)[P(VDF-TrFE) or PVTF] have attracted growing interest in developing flexible devices because of their excellent ferroelectricity and piezoelectricity. High coercive field(E_c) inherent to PVTF for switching its polarization, however, is not beneficial for practical memory or sensor device application. Different strategies, including irradiation and interface control, have been thus developed to reduce E_c. Despite many efforts, a facile approach to tailoring intrinsic E_c of PVTF has not been documented. In this work, an optically controlled E_c was reported, which is achieved for the first time by introducing photosensitive MAPbI₃ nanocrystals into PVTF matrix. When exposed to the irradiation of 532 nm laser light, a decreased E_c of the composites can be achieved reversibly by increasing the light density. The decreased level of E_c increases as the MAPbI₃ content enhanced, and a 10.7% reduction of E_c can be achieved in 15%(mass fraction) MAPbI₃/PVTF samples. These results could be attributed to loading an internal stress on PVTF, which was generated by the photostriction of MAPbI₃ nanocrystals. This explanation was further supported by in-situ XRD results under irradiation of 532 nm laser light. Our findings may offer the opportunity to optically modulate the ferroelectric properties of PVTF composites for optimized device performances.

Key words: Poly(vinylidene fluoride-trifluoroethylene)[P(VDF-TrFE)], MAPbI₃, Photostriction, Optically controlled coercive field