Lai Sin Ki, Luk Chi Man, Tang Libin, Teng Kar Seng, Lau Shu Ping
Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon HKSAR, Hong Kong.
Nanoscale. 2015 Mar 12;7(12):5338-43. doi: 10.1039/c4nr07565j.
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.
聚苯胺功能化石墨烯量子点(PANI-GQD)和原始石墨烯量子点(GQD)被用于光电器件。与基于GQD的光电探测器相比,基于PANI-GQD的光电探测器表现出更高的响应度,在405 nm处约高一个数量级,在532 nm处高7倍。光响应的改善归因于岛状聚合物基质增强了GQD的互连,这有利于聚合物基质内的载流子传输。还展示了PANI-GQD的光学可调电流-电压(I-V)滞后现象。在±1 V的扫描范围内,滞后现象随光强度逐渐增大。当偏压达到4 V时,GQD和PANI-GQD器件的光电流均从正变为负。随着偏压增加,光生载流子被激发到GQD中的俘获态。被俘获的电荷与从电极注入的电荷相互作用,导致自由电荷载流子净减少和负光电流。GQD和PANI-GQD器件中的光电流切换现象可能会在光电子学中开辟新的应用。