Piezo-phototronic effect in highly stable lead-free double perovskite Cs2SnI6-PVDF nanocomposite: Possibility for strain modulated optical sensor

Metal halide perovskites (MHPs) are highly emerging materials for their applications in the field of photovoltaics and optoelectronics. However, beyond these applications, the MHPs have been proven to be excellent candidates for the fabrication of self-powered nanogenerators on their own or in conjunction with piezoelectric polymers such as poly(vinylidene-fluoride) (PVDF). More so, lead-free MHPs are the need of hour, which opens up the possibility of a sustainable future. Additionally, in piezoelectric composite films containing MHP, it is possible to utilize the coupling of photoexcitation, semiconducting and piezoelectric properties, which leads to the piezo-phototronic effect. Here, we report the fabrication of Cs2SnI6-PVDF (CSIP) composite, where the synthesis of Cs2SnI6 nanoparticles was realized in an in-situ approach. Notably, the Cs2SnI6 nanoparticles nucleates 100% electroactive β- and γ-phases in PVDF which gives rise to the intrinsic piezoelectric nature of the lead free composite film. Furthermore, to decipher the interfacial interaction between Cs2SnI6 and PVDF first principle DFT study was performed which unravels the non-bonding interaction between the Cs2SnI6 and PVDF. The piezo-phototronic effect was successfully realized in the CSIP film indicating its promising use in the piezotronics sensor. Moreover, the CSIP films were utilized as a piezoelectric nanogenerator, which shows superior piezoelectric output voltage of 9 V and current of 5 μA. It can also be utilized in human physiological signal monitoring, as well as a pressure sensor. Hence, the combined properties of semiconducting, photoexcitation and piezoelectricity in the CSIP films can be utilized in both mechanical energy harvesting and piezotronics sensing applications.