Using Strain Engineering To Improve The Performance Of Flexible Self-powered Perovskite Photodetector

Flexible self-powered photodetector（FSPPD）has the advantages of battery free,light weight,portability and compatibility with wearable devices.It shows great potential applications in the development of next-generation nano devices and the Internet of things.Metal halide perovskites（MHPs）have been widely studied in the past decade for their excellent photoelectric properties,such as good light absorption,tunable band gap,long carrier lifetime and diffusion length,shallow defect energy level and strong spin-orbit coupling（SOC）.Comparing with traditional inorganic semiconductors like Si,Ga As and Ga N which achieve huge success in PD,metal halide perovskites are more suitable for developing high-performance FSPPD because of relatively soft crystal lattice due to their weak bonding nature.The traditional methods to improve the performance of perovskite optoelectronic devices mainly include additive engineering and interface engineering.However,the soft perovskite lattice makes the internal stress easier to change.The stress will affect defects,carrier recombination,band gap and spin orbit coupling,which can directly affect the crystal structure and photoelectric properties of materials.Therefore,stress engineering is an effective way to control the quality of thin films and the efficiency of devices.This paper studies the internal mechanism of stress engineering to regulate the internal photoelectric properties of perovskite,so as to increase the function of flexible self-powered perovskite photodetector（FSPPPD）.In this work,we insert an additional hole transport layer pdcbt into the heterojunction flexible self powered perovskite photodetector to regulate the thermal expansion coefficient of the hole transport layer in direct contact with the perovskite film,so as to change the internal stress of the perovskite film.X-ray diffraction analysis shows that the perovskite films grown on pdcbt layer produce out of plane compressive stress and in-plane tensile stress.The change of perovskite lattice stress will change the crystal structure and then affect the spin orbit coupling.The experimental results of linear polarization/circularly polarized light excitation modulation photocurrent and magneto-optic current show that the spin orbit coupling of perovskite films prepared on PDCBT layer is enhanced.Under the stronger spin orbit coupling,the Rashba effect is enhanced,which narrows the perovskite band gap and increases the carrier life,and finally improves the performance of the flexible self powered perovskite photodetector.At 660nm,the response of the flexible self powered perovskite photodetector optimized by stress engineering reaches 0.39A/W and the detection rate reaches 2.31*10¹³Jones,which is very competitive in FSPPD.Other performance indexes are also improved compared with standard devices without PDCBT.