Organic solar cells have the characteristics and advantages of flexibility, light weight, wide source of materials, large-area printing and preparation, and have great application potential and development prospects in building integration, wearable equipment, etc. However, compared with inorganic photovoltaic devices, the energy conversion efficiency of organic solar cells is still low. Both theory and experiment have proved that the laminated device is an effective way to improve the efficiency of solar cell devices, especially for organic solar cells. It can not only reduce the heat loss of single-junction organic solar cells, but also give full play to the advantages of the adjustable structure and performance of organic molecules to meet the different requirements of different active layers in the laminated device for the solar spectral absorption range. In the construction of high-efficiency stacked devices, how to balance the open circuit voltage (Voc) and short circuit current density (Jsc) of the front and rear sub-cells is crucial to improve the overall performance of the stacked devices, and it is also an important challenge to build the stacked devices.
In the preliminary work, the research team of Professor Chen Yongsheng and Professor Wan Xiangjian of Nankai University, in cooperation with the research group of researcher Ding Liming of the National Nanoscience Center, put forward a semi-empirical model, which can effectively guide the design of front and rear sub-cell materials of organic laminated photovoltaic devices. Based on this model, they used molecule F-M with receptor-donor-receptor (A-D-A) structure as the precursor cell receptor, and O6T-4F as the aftercell receptor molecule to build a series of stacked devices with a photoelectric conversion efficiency (PCE) of 17.3%, refreshing the efficiency record of the field at that time.
Figure 2. (a) Layered device structure; (b) Energy level diagram of laminated device; (c) Optical simulation results; (d) J-V curve; (e) EQE curve of the best laminated device; (f) Photovoltaic parameter-light intensity dependence curve.
See: Lingxian Meng, Huahe Liang, Guangkun Song, Mingpeng Li, Yuzhong Huang, Changzun Jiang, Kai Zhang, Fei Huang, Zhaoyang Yao, Chenxi Li, Xiangjiang Wan&Yongsheng Chen Tandem organic solar cells with efficiency over 19% via the careful subcell design and optimization. Sci. China Chem. 2022, DOI: 10.1007/s11426-022-1479-x.