Comparison of photoresponse of transistors based on graphene-quantum dot hybrids with layered and bulk heterojunctions

Phototransistors based on graphene-quantum dot hybrids have a high responsivity and gain. However, the influence of the type of heterojunction on the photoresponse of the transistors is still undetermined. A comparison was performed on field-effect phototransistors (FEpTs) with two types of heterojunctions: layered heterojunctions (LHs) and bulk heterojunctions (BHs). Through a comparative study, it was shown that BH-FEpTs had electron and hole mobilities (μE and μH) of 677 and 527 cm(2) V(-1) s(-1) whereas LH-FEpTs had lower mobilities of μE = 314 cm(2) V(-1) s(-1) and μH = 367 cm(2) V(-1) s(-1). The large interfacial area in the BHs reduced the degree of channel order (α) by two orders of magnitude compared with the LHs. Although a higher mobility was achieved, an increase in the degree of channel disorder and the lack of an effective transfer mechanism limits the responsivity in BH-FEpTs. Therefore, LH-FEpTs are more appropriate candidates for near infrared phototransistors.

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