Hybrid Interfacial Engineering: An Enabling Strategy for Highly Sensitive and Stable Perovskite Quantum Dots/Organic Heterojunction Phototransistors

All-inorganic lead halide perovskite quantum dots (PQD) have attracted tremendous research interest in the field of phototransistors due to their excellent optoelectronic properties. However, the inefficient charge transport/extraction and high trap-state density of the assembled PQD films seriously limit the photoresponsivity of PQD-based phototransistors. Herein, we demonstrate that these limits can be overcome by adopting a novel device architecture composed of a polar-polymer capping layer on a PQD/organic semiconductor (OSC) heterojunction. The polar polymer film plays the role of both electron trapping and encapsulation, whereas OSC provides the fast transport tracks for charges and PQD serves as the photoactive materials. Owing to the balanced dynamic processes of photogenerated charges, highly sensitive photodetection is achieved, as demonstrated by the peak photosensitivity of 1.5 × 104, a photoresponsivity of 2.1 × 104 A/W, a detectivity of 1 × 1015 Jones, and a high gain of 6.4 × 104 under weak incident light of 3 μW/cm2. Additionally, the phototransistors exhibit superior stability and reproducibility with negligible changes in the output current both in darkness and under illumination after storing for 4 months. The results demonstrate the promising potentials of the polar polymer/PQD/OSC heterojunction for high-performance photodetectors, and the mechanism and strategy described here can be applied to other kinds of quantum dots-based optoelectronic devices.