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Low cost, high absorption coefficient, tunable band gap, and compatibility with flexible devices make lead sulfide (PbS) quantum dots (QDs) based photoconductors promising candidates for next-generation near-infrared (NIR) photodetectors. However, the detection performance of PbS QDs-based photoconductors still needs to be further improved, because there is a trade-off among the responsivity/detectivity/bandwidth in the device development process, that is, it is difficult to improve the three parameters simultaneously. Inspired by the design idea of sensitized phototransistor, a kind of amorphous indium gallium zinc oxide (a-IGZO)/PbS QDs heterojunction photoconductor is reported in this paper. The most prominent feature of this work is that a-IGZO, like a photocurrent “amplifier”, increases the photocurrent by several orders of magnitude without generating additional noise, and thus improves the sensitivity and responsiveness of the device. Compared with the initial pure PbS QDs-based photoconductor, the heterojunction device is able to increase the photocurrent by 3000 times together with a low dark current, and improve the response speed of the device with the help of interface-assisted carrier separation and recombination. In the NIR band, the device exhibits an exciting performance with a detectivity of 1.53 × 10 13 Jones, a responsivity of 19070 mA/W and a decay time of 0.39 ms, respectively. By applying the a-IGZO/PbS QDs heterojunction to paper-based devices, a flexible device with bending resistance can be obtained, and the detection performance of the device does not deteriorate after 1000 times of bending.
Zhang et al. (Thu,) studied this question.