During a joint Russian-Chinese study, an organic solar battery with an efficiency > 18% was created

Organic solar cells (OSC) are one of the most promising renewable energy technologies due to their low cost, flexibility and lightness, as well as the ability to produce large area devices using web printing. Active development of new donor and acceptor materials for the active layer of OSC, which has been carried out in recent years around the world, has made it possible to obtain OSC with an energy conversion efficiency above 19%. Among the acceptor materials, non-fullerene acceptors (NFAs), which, as a rule, have an acceptor-donor-acceptor (A-D-A) architecture, have wide functionalization possibilities for fine-tuning energy levels, as well as high light absorption capacity in the visible and near IR regions.

Scientists of the Laboratory of Polysulfur-Nitrogen Heterocycles of the Zelinsky Institute in collaboration with colleagues from Nankai University (Tianjin, China), modified the model NFAs known since 2019, which is the Y6 molecule containing an electron-deficient central core based on condensed 2,1,3-benzothiadiazole. The purpose was optimization of the energy levels, improving molecular planarity, as well as intermolecular charge transfer. It was found that the replacement of the long alkyl chain in the central cluster by 4-alkoxyphenyl substituents made it possible to avoid the use of tin-containing reagents in the synthesis and to obtain target structures from cheaper and more accessible substrates. The study of the effect of the length of the alkyl radical of the 4-alkoxyphenyl group showed a slight difference in the properties of dyes with butoxy, hexyloxy, and octyloxy groups. However, the medium-long chain sensitizer, when mixed with the donor polymer material PM6, made it possible to obtain active layer films with better morphology, which led to the design of a device with a photovoltaic efficiency of 17.59%, which also demonstrated high stability due to improved crystalline properties, more effective separation of excitons and a reduced process of charge recombination. When using Y6 as the third component of the active layer, scientists were able to increase the photovoltaic efficiency of OSB up to 18%.

Source:

Zhixiang Li, Changzun Jiang, Xin Chen, Guangkun Song, Xiangjian Wan, Bin Kan, Tainan Duan, Ekaterina A. Knyazeva, Oleg A. Rakitin, Yongsheng Chen Side-chain Modification of Non-fullerene Acceptors for Organic Solar Cells with Efficiency over 18% // J. Mater. Chem. C, 2023, 11, 6920-6927. DOI: 10.1039/D3TC00820G.