Hierarchical Heterojunction Enhanced Photodoping of Polymeric Semiconductor for Photodetection and Photothermoelectric Applications

The realization of efficient photodoping of polymeric semiconductors (PSCs) is crucial for the construction of high-performance photodetectors and photothermoelectric devices. Traditional layer or bulk heterojunction can enhance the photodoping of PSCs but suffers from a trade-off in balancing photocarrier generation and charge transport. Herein, we report on a hierarchical heterojunction comprising a bulk heterojunction photoactive layer and a separate charge transport layer, fabricated by using a simple orthogonal solvent method. The well-designed interfacial energy-level alignment of the hierarchical heterojunction contributes to efficient exciton separation and charge transfer into the charge transport layer, thus resulting in improved photodetection and photothermoelectric conversion. The photodetector exhibits photosensitivity and photoresponsivity of up to 1.1 × 107 and 9.2 × 106 A W–1, respectively, while the photothermoelectric device displays a maximum power factor of 13.7 μW m–1 K–2. These results indicate that hierarchical heterojunction-enhanced photodoping can serve as a powerful strategy to enable the multifunctional applications of PSCs.