Facile method for the preparation of high-performance photodetectors with a GQDs/perovskite bilayer heterostructure

A high-performance nitrogen doped graphene quantum dots (GQDs)/all-inorganic (CsPbBr₃) perovskite nanocrystals (NCs) heterostructure photodetector was fabricated on a quartz substrate, using the low cost spin coating technique followed by hot plate annealing. The GQDs/CsPbBr₃ NCs heterostructure photodetector exhibits a high overall performance with a photoresponsivity of 0.24 AW⁻¹, on/off ratio of 7.2 × 10⁴, and specific detectivity of up to 2.5 × 10¹² Jones. The on/off ratio of the hybrid device was improved by almost ten orders of magnitude, and the photoresponsivity was enhanced almost three times compared to the single layer perovskite NCs photodetector. The performance enhancement of the hybrid device was due to its highly efficient carrier separation at the GQDs/CsPbBr₃ NCs interface. This results from the coupling of the GQDs layer, which efficiently extracts and transports the photogenerated carriers, with the CsPbBr₃ NCs layer, which has a large absorption coefficient and high quantum efficiency. The interfacial charge transfer from the CsPbBr₃ NCs to the GQDs layer was demonstrated by the quenching in the photoluminescence (PL) spectra, and the fast-average decay time in the time-resolved photoluminescence (Trpl) spectra of the hybrid photodetector. Moreover, the performance-enhancement mechanism of the hybrid GQDs/CsPbBr₃ photodetector was elucidated by analyzing the band alignment of the GQDs and CsPbBr₃ under laser illumination.