Balancing light absorptivity and carrier conductivity of graphene quantum dots for high-efficiency bulk heterojunction solar cells
- Balancing light absorptivity and carrier conductivity of graphene quantum dots for high-efficiency bulk heterojunction solar cells
- 김정규; 박명진; 김상진; Dong Hwan Wang; Sung Pyo Cho; 배수강; 박종혁; 홍병희
- Light Absorptivity; Carrier Conductivity; Graphene Quantum Dot; Bulk Heterojunction; Solar Cells; light absorption
- Issue Date
- ACS Nano
- VOL 7, NO 8, 7207-7212
- Graphene quantum dots (GQDs) have been considered as a novel material because their electronic and optoelectronic properties can be tuned by controlling the size and the functional groups of GQDs. Here we report the synthesis of reduction-controlled GQDs and their application to bulk heterojunction (BHJ) solar cells with enhanced power conversion efficiency (PCE). Three different types of GQDs—graphene oxide quantum dots (GOQDs), 5 h reduced GQDs, and 10 h reduced GQDs—were tested in BHJ solar cells, and the results indicate that GQDs play an important role in increasing optical absorptivity and charge carrier extraction of the BHJ solar cells. The enhanced optical absorptivity by rich functional groups in GOQDs increases short-circuit current, while the improved conductivity of reduced GQDs leads to the increase of fill factors. Thus, the reduction level of GQDs needs to be intermediate to balance the absorptivity and conductivity. Indeed, the partially reduced GQDs yielded the outstandingly improved PCE of 7.60% in BHJ devices compared to a reference device without GQDs (6.70%).
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