High-Performance White-Light Detection of Inorganic/Perovskite Mixed Quantum Dot Layers Fabricated by Drop-Casting Methods

CdZnS/ZnS + CsPbBr
₃
 + InP/ZnSeS mixed quantum dot (QD) based metal–semiconductor–metal photodetectors (MSM PDs) for white-light detection were fabricated successfully by low-cost drop-cast methods. The photoluminescence (PL) spectra reveal emission peaks of ∼ 430 nm (blue light), ∼515 nm (green light), and ∼600 nm (red light) for CdZnS/ZnS, CsPbBr
₃
, and InP/ZnSeS QDs, respectively. Furthermore, CdZnS/ZnS + CsPbBr
₃
 + InP/ZnSeS mixed QDs exhibit a broad absorption spectrum from ultraviolet (UV) to infrared (IR), in contrast to the narrower absorption range of CdZnS/ZnS, CsPbBr
₃
, and InP/ZnSeS QDs. The morphology and size of CdZnS/ZnS (∼10 nm), CsPbBr
₃
(∼12 nm), and InP/ZnSeS (∼ 5 nm) QDs were investigated using high-resolution transmission electron microscopy (HRTEM). With switching on/off white-light illumination, CdZnS/ZnS + CsPbBr
₃
 + InP/ZnSeS mixed QD-based MSM PDs exhibit outstanding performance attributed to the broadband light absorption of the mixed QDs, including an ultra-high photo-to-dark current ratio (PDCR: ∼590), high detectivity (up to ∼0.7 × 10
¹⁰
cm Hz
^1/2
/W), and fast operation speed (rise time and fall time: ∼150 ms). Compared to the CdZnS/ZnS + InP/ZnSeS mixed QD-based PDs, the CdZnS/ZnS + CsPbBr
₃
 + InP/ZnSeS mixed QD-based PDs show better photoresponse, resulting from higher photocurrent levels by an increase in green light absorption and a decrease in band offset at the interface after adding CsPbBr
₃
QDs. These results support the use of the inorganic/perovskite mixed QD-based PDs in next-generation broadband photodetection.