Low-temperature synthesis of all-inorganic perovskite nanocrystals for UV-photodetectors

Controllable synthesis of tin-doped all-inorganic perovskite (e.g. CsPb1-XSnXBr3) nanocrystals while maintaining tin at the divalent state is of great importance for tuning their optoelectronic properties by changing the chemical composition and geometrical size; however, this remains a non-negligible challenge. In contrast to the conventional high-temperature (>150 degrees C) synthesis reaction that would more likely facilitate oxidation of divalent Sn2+ to quadrivalent Sn4+, this work demonstrates a facile low-temperature (105-150 degrees C) hot-injection method to synthesize quantum-confined Sn2+-doped CsPb1-XSnXBr3 nanocrystals with sizes ranging from approximate to 6.2 nm to approximate to 8.3 nm depending on the reaction temperature. The optimized reaction temperature of 135 degrees C led to a Sn2+-doping ratio of 3.4% in CsPb1-XSnXBr3 nanocrystals which exhibited uniform nanoplatelets with an average lateral size of approximate to 7.4 nm. Furthermore, for the first time, we show that the perovskite nanocrystals are promising for the development of low-cost and trap-assisted photomultiplication UV-photodetectors, and the photodetectors based on CsPb0.966Sn0.034Br3 nanocrystals exhibited wavelength-dependent detectivities in the magnitude of 10(11) Jones for UV light extending from 310 nm to 400 nm at a reverse bias of -7 V. The high EQE of approximate to 1940% at around 340 nm indicates that the devices had a gain at the large reverse bias condition, which is attributed to the formation of interfacial traps by CsPb0.966Sn0.034Br3 nanocrystals that can make the electron injection barrier thin enough to allow electron tunneling in the photodetectors for photomultiplication.