Solution-processed nitrogen-doped graphene quantum dots/perovskite composite heterojunction for boosting performance of anatase titanium dioxide (TiO2)-based UV photodetector

In this work, a facile and low-cost method is introduced to boost performance of TiO2-based UV photodetector (PD). The method involves addition of a solution-processed GQDs-CsPbBr3 composite layer to the TiO2 film to fabricate a high-performance and stable hybrid photodetector based on TiO2/GQDs-CsPbBr3 bilayer heterojunction. The TiO2/GQDs-CsPbBr3 bilayer heterojunction was characterized with several techniques. The ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectrometers reveal that the absorption and emission of the TiO2/GQDs-CsPbBr3 bilayer heterojunction have significantly enhanced compared with that of the anatase TiO2 film, without the GQDs-CsPbBr3 composite layer. In addition, The hybrid photodetector shows a low dark current (I-D = 0.13 nA), a high light current (I-L = 343,626 nA), an on/off ratio (2.69 x 10(6)), a responsivity (R = 7.11 A/W), and a specific detectivity (D* = 3.32 x 10(13) J). The responsivity of the hybrid was improved by 64 times in magnitudes compared with that of the TiO2 without the GQDs-CsPbBr3 composite layer. Moreover, the performance of the hybrid photodetector not only outdo the performance of reported PDs based on wide bandgap materials/perovskite and 2D materials/2D materials bilayer heterostructure, but also performance of PDs based on 2D materials/2D materials/2D materials and silicon/2D materials/2D materials triple-layer heterostructure. The enhanced performance of the hybrid PD was due to the excellent alignment between the anatase TiO2, GQDs, and CsPbBr3, which enabled the TiO2/GQDs-CsPbBr3 bilayer heterojunction to reduce recombination process and increase photon-absorption rate. These results pave the way for enhancing the wide bandgap materials-based UV optoelectronics with the solution-processed and low-cost GQDs-CsPbBr3 composite.