High-Performance Short-Wave-Infrared Imager Based on the PbS Quantum Dot/Organic BHJ Hybrid Structure

Short-wave-infrared (SWIR) photodetectors (PDs) have attracted great interest for advanced active imaging applications. Compared with epitaxially grown inorganic semiconductors, quantum dots (QDs) and organic semiconductors have been regarded as promising candidates for infrared sensing due to the solution processibility and monolithic integrated ability with silicon-based readout circuits. However, owing to high dark currents, achieving sensitive photodetection remains a big challenge for solution-processed SWIR PDs. Herein, we report a high-performance photodiode with the PbS QD/organic bulk-heterojunction (BHJ) hybrid structure, which exhibited a low dark current density of $1.89\times 10^{\mathbf {-{7}}}$ A $\cdot $ cm ${}^{\mathbf {-{2}}}$ and a high specific detectivity of $2.0\times 10^{\boldsymbol {\textbf {12}}}$ Jones at 1520 nm at room temperature. By integrating with a CMOS read-out circuit ( $640\times 512$ pixels), a high-performance SWIR imager has been successfully fabricated with a solution-processed approach. Systematic analyses suggest the PbS QD/organic BHJ hybrid structure not only suppressed the trap-assisted recombination, but also improved the charge transport and extraction, as well as enhanced the photosensitivity and response speed.