SKKU Advanced Institute of Nano Technology and School of Chemical Engineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea.
ACS Nano. 2013 Aug 27;7(8):7207-12. doi: 10.1021/nn402606v. Epub 2013 Aug 2.
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%).
石墨烯量子点（GQDs）因其电子和光电性质可以通过控制 GQDs 的尺寸和官能团来调节而被认为是一种新型材料。在这里，我们报告了还原控制的 GQDs 的合成及其在具有增强的功率转换效率（PCE）的体异质结（BHJ）太阳能电池中的应用。在 BHJ 太阳能电池中测试了三种不同类型的 GQDs——氧化石墨烯量子点（GOQDs）、5 h 还原 GQDs 和 10 h 还原 GQDs——结果表明 GQDs 在提高 BHJ 太阳能电池的光吸收和载流子提取方面起着重要作用。GOQDs 中丰富的官能团提高了光吸收能力，增加了短路电流，而还原 GQDs 的导电性提高则导致填充因子增加。因此，GQDs 的还原水平需要处于中间状态以平衡吸收能力和导电性。实际上，部分还原的 GQDs 在 BHJ 器件中产生了卓越的 7.60%的 PCE，而没有 GQDs 的参考器件的 PCE 为 6.70%。
