Ultrahigh Detectivity Colloidal Quantum dot Avalanche Photodetectors Driven by Electron Mobility of the n‐Type Layer

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Colloidal quantum dots (CQDs) are pragmatic candidates for infrared photodetectors due to their high absorption coefficient in the infrared region and solution processability. In addition, an incorporation of avalanche multiplication within the CQD region offers a route to achieve ultrahigh detectivity ( D * ) in CQD‐based infrared photodetectors. Herein, we clarify how the electron mobility of n‐type layer would affect to the detection performances in the CQD‐based avalanche photodetector (CQD‐APD). The introduction of ZnO nanoparticles (NPs) having high electron mobility as n‐type layer suppresses the electron accumulation at the CQD/n‐type interfaces, thereby mitigating the defect‐mediated trapping‐detrapping processes and reducing the flicker noise current in our CQD‐APD. Moreover, the reduction of accumulated electrons alleviates a formation of potential barrier at CQD/n‐type interfaces, enabling the initiation of avalanche multiplication with lower energy threshold. Our CQD‐APD with optimal n‐type layer demonstrates an outstanding multiplication gain exceeding 400 and a peak detectivity of 1.4 × 10 15 Jones at a wavelength of 940 nm.