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

摘要

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 (mu(E) and mu(H)) of 677 and 527 cm(2) V-1 s(-1) whereas LH-FEpTs had lower mobilities of mu(E) = 314 cm(2) V-1 s(-1) and mu(H) = 367 cm(2) V-1 s(-1). The large interfacial area in the BHs reduced the degree of channel order (alpha) 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.