title: Photoresponse of polyaniline-functionalized graphene quantum dots.
abstract: Polyaniline-functionalized graphene quantum dots (PANI-GQD) and pristine graphene quantum dots (GQDs) were utilized for optoelectronic devices. The PANI-GQD based photodetector exhibited higher responsivity which is about an order of magnitude at 405 nm and 7 folds at 532 nm as compared to GQD-based photodetectors. The improved photoresponse is attributed to the enhanced interconnection of GQD by island-like polymer matrices, which facilitate carrier transport within the polymer matrices. The optically tunable current-voltage (I-V) hysteresis of PANI-GQD was also demonstrated. The hysteresis magnifies progressively with light intensity at a scan range of ±1 V. Both GQD and PANI-GQD devices change from positive to negative photocurrent when the bias reaches 4 V. Photogenerated carriers are excited to the trapping states in GQDs with increased bias. The trapped charges interact with charges injected from the electrodes which results in a net decrease of free charge carriers and a negative photocurrent. The photocurrent switching phenomenon in GQD and PANI-GQD devices may open up novel applications in optoelectronics.
authors.affiliation: Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon HKSAR, Hong Kong.
authors.forename: Sin Ki
authors.initials: SK
authors.lastname: Lai
authors.forename: Chi Man
authors.initials: CM
authors.lastname: Luk
authors.forename: Libin
authors.initials: L
authors.lastname: Tang
authors.forename: Kar Seng
authors.initials: KS
authors.lastname: Teng
authors.forename: Shu Ping
authors.initials: SP
authors.lastname: Lau