Kawashima Kazuaki, Tamai Yasunari, Ohkita Hideo, Osaka Itaru, Takimiya Kazuo
Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8527, Japan.
RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
Nat Commun. 2015 Dec 2;6:10085. doi: 10.1038/ncomms10085.
A crucial issue facing polymer-based solar cells is how to manage the energetics of the polymer/fullerene blends to maximize short-circuit current density and open-circuit voltage at the same time and thus the power conversion efficiency. Here we demonstrate that the use of a naphthobisoxadiazole-based polymer with a narrow bandgap of 1.52 eV leads to high open-circuit voltages of approximately 1 V and high-power conversion efficiencies of ∼9% in solar cells, resulting in photon energy loss as small as ∼0.5 eV, which is much smaller than that of typical polymer systems (0.7-1.0 eV). This is ascribed to the high external quantum efficiency for the systems with a very small energy offset for charge separation. These unconventional features of the present polymer system will inspire the field of polymer-based solar cells towards further improvement of power conversion efficiencies with both high short-circuit current density and open-circuit voltage.
基于聚合物的太阳能电池面临的一个关键问题是如何调控聚合物/富勒烯共混物的能量，以同时最大化短路电流密度和开路电压，进而提高功率转换效率。在此，我们证明，使用带隙为1.52 eV的窄带隙萘并双恶二唑基聚合物，可使太阳能电池的开路电压高达约1 V，功率转换效率约为9%，光子能量损失低至约0.5 eV，远低于典型聚合物体系（0.7 - 1.0 eV）。这归因于电荷分离能量偏移极小的体系具有较高的外量子效率。当前聚合物体系的这些非常规特性将推动基于聚合物的太阳能电池领域进一步提高功率转换效率，同时实现高短路电流密度和高开路电压。
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