Vacuum-filtration enabled large-area CsPbBr3 films on porous substrates for flexible photodetectors

All-inorganic perovskites (CsPbX3, X = Br, Cl, I) have been considered as promising candidates for developing high-performance, flexible and lightweight optoelectronic devices due to their high absorption coefficient, mechanical durability, low-temperature synthesis ability and stable physiochemical properties. However, the fabrication of pinhole-free, large-scale inorganic perovskite films is still a great challenge, because it is limited by strong chemical bonds and really low solubility, impeding their application in flexible solar cells, photodetectors and light emitting diodes. In this paper, a vacuum-filtration method to deposit large-scale, compact all-inorganic perovskite films from nanosheet suspensions on arbitrary porous substrates, which allows control of the uniformity and thickness of the perovskite films, is reported. The performance of the fabricated flexible-photodetectors was greatly improved by adding a proper amount of carbon nanotube (CNT) additive, which could maintain the low dark current density and increase the photo-responsivity by suppressing the photocarrier recombination. The improved photodetectors showed a large on/off ratio of >1 × 104, and a fast rise/decay time of 52/14 ms. These flexible photodetectors demonstrated excellent mechanical bending capabilities with retained performance after 1000 bending cycles. This deposition method could provide a universal route for preparing inorganic material films for fundamental studies and practical applications.