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

Abstract

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.

Role of Interfacial Interactions in the Graphene-Directed Assembly of Monolayer Conjugated Polymers

“…85,86 Similarly, well-aligned interfacial energy levels in photovoltaic devices are crucial for efficient exciton separation at donor−acceptor interfaces and charge transport across electron/hole transporting layers to respective electrodes. 87 To that end, the ability to shift energy levels of polymers or dope them by simply assembling them on graphene/F-graphene substrates and without having to undergo a synthetic route is highly beneficial.…”

“…The frontier energy levels of polymers play critical roles in the performance of electronic devices. For instance, in OFET devices, the energy levels between the polymer and the electrode should match to reduce the contact resistance and therefore eliminate high operating voltages. , Similarly, well-aligned interfacial energy levels in photovoltaic devices are crucial for efficient exciton separation at donor–acceptor interfaces and charge transport across electron/hole transporting layers to respective electrodes . To that end, the ability to shift energy levels of polymers or dope them by simply assembling them on graphene/F-graphene substrates and without having to undergo a synthetic route is highly beneficial.…”

Advances in Organic Thermoelectric Devices for Multiple Applications

“…developed an improved photodoping method inspired from OPVs by incorporating an unique hierarchical heterojunction, which is consisted of a bulk heterojunction photoactive IDTBT:PC61BM layer and a separate PDPP4T charge transport layer (Figure 14f). [ 97 ] Due to the well‐designed energy level structure, the P‐TE device achieved effective photodoping with power factors reach up to 13.7 µW m −1 K −2 (Figure 14g). A prototype photodetector array and flexible P‐TE power generator is fabricated (Figure 14h,i), proving the potential of photodoping for applications in low power consumption wearable devices.…”

“…i) Prototype flexible P-TE power generator and it power output curves in dark environment as well as under light irradiation. Reproduced with permission [97]. Copyright 2022, American Chemical Society.…”