All polymer solar cells have attracted attention due to their excellent transparency, solution processability, and excellent mechanical flexibility. Due to the long conjugated molecular skeleton and high molecular weight of polymers, the microstructure is difficult to control, which limits the short-circuit current density and filling factor of all polymer solar cells. In addition, as a key factor in evaluating the application prospects, there is no clear and unified evaluation standard between the stress-strain characteristics and mechanical stability of flexible devices, which restricts the development of photovoltaic device performance and mechanical stability, and confuses future research directions.
Recently, the research group of advanced organic functional materials and devices led by Bao Xichang, a researcher at the Chinese Academy of Sciences Qingdao Institute of Bioenergy and Process Research, designed small molecules with phenylalkyl side chains as solid additives, which, with the help of the characteristic side chains, interacted with the multiple non covalent interactions generated by polymer receptors. In particular, a new non covalent bond was formed between the phenyl of the additive phenylalkyl and the end group of the receptor, which improved the intermolecular interaction intensity and orderliness of the PY-IT subcrystalline phase, and improved the photovoltaic performance and mechanical stability of the all polymer solar cells. By independently inducing molecular stacking and vertical phase separation, all polymer solar cells with pseudo planar heterojunctions achieved an efficiency of 19.01% and a filling factor of nearly 80%, which is currently one of the highest values in all polymer solar cells. At the same time, researchers have explored the changes in various variables such as fracture elongation, toughness, elastic deformation, elastic modulus, and yield strength under stress and strain, and found that compared with traditional fracture elongation and elastic modulus, the elastic deformation of the active layer can more accurately reflect the phase separation self-healing ability and bending stability of the device. This provides research ideas for the development of advanced all polymer solar cells with excellent performance and mechanical flexibility.
The relevant research results are published in Energy&Environmental Science. The research work has received support from the National Natural Science Foundation of China, the Postdoctoral Science Foundation of China, the Special Fund of Shandong Energy Research Institute, and the Shandong Province Postdoctoral Innovation Talent Support Program.
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