Cheng Pei, Wang Hao-Cheng, Zheng Ran, Zhu Yuan, Dai Shuixing, Li Zeyuan, Chen Chung-Hao, Zhao Yepin, Wang Rui, Meng Dong, Zhu Chenhui, Wei Kung-Hwa, Zhan Xiaowei, Yang Yang
Department of Materials Science and Engineering, California NanoSystems Institute, University of California, Los Angeles, CA, 90095, USA.
Department of Materials Science and Engineering, Center for Emergent Functional Matter Science, National Chiao Tung University, Hsinchu, 30050, Taiwan.
Adv Mater. 2020 Sep;32(38):e2002315. doi: 10.1002/adma.202002315. Epub 2020 Aug 16.
In tandem organic photovoltaics, the front subcell is based on large-bandgap materials, whereas the case of the rear subcell is more complicated. The rear subcell is generally composed of a narrow-bandgap acceptor for infrared absorption but a large-bandgap donor to realize a high open-circuit voltage. Unfortunately, most of the ultraviolet-visible part of the photons are absorbed by the front subcell; as a result, in the rear subcell, the number of excitons generated on large-bandgap donors will be reduced significantly. This reduces the (photo) conductivity and finally limits the hole-transporting property of the rear subcell. In this work, a simple and effective way is proposed to resolve this critical issue. To ensure sufficient photogenerated holes in the rear subcell, a small amount of an infrared-absorbing polymer donor as a third component is introduced, which provides a second hole-generation and transporting mechanism to minimize the aforementioned detrimental effects. Finally, the short-circuit current density of the two-terminal tandem organic photovoltaic is significantly enhanced from 10.3 to 11.7 mA cm (while retaining the open-circuit voltage and fill factor) to result in an enhanced power conversion efficiency of 15.1%.
在串联有机光伏电池中，前子电池基于大带隙材料，而后子电池的情况则更为复杂。后子电池通常由用于红外吸收的窄带隙受体和用于实现高开路电压的大带隙供体组成。不幸的是，光子的大部分紫外 - 可见部分被前子电池吸收；结果，在后子电池中，在大带隙供体上产生的激子数量将显著减少。这降低了（光）电导率，最终限制了后子电池的空穴传输性能。在这项工作中，提出了一种简单有效的方法来解决这个关键问题。为了确保后子电池中有足够的光生空穴，引入了少量作为第三组分的红外吸收聚合物供体，它提供了第二种空穴产生和传输机制，以最小化上述有害影响。最后，两端串联有机光伏电池的短路电流密度从10.3显著提高到11.7 mA cm（同时保持开路电压和填充因子），从而使功率转换效率提高到15.1%。
