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    Home > Wei Zhixiang research group of national Nano Science Center has made important progress in the research of all small molecular organic solar cells

    Wei Zhixiang research group of national Nano Science Center has made important progress in the research of all small molecular organic solar cells

    • Last Update: 2020-01-27
    • Source: Internet
    • Author: User
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    Recently, Wei Zhixiang, Lu Kun, researcher of national Nano Science Center, cooperated with Gao Feng, Professor of linxueping University, Sweden, and Ma Wei, Professor of Xi'an Jiaotong University to make important progress in the design of all small molecular organic solar cell materials and the research of device performance, and achieved 14.34% through multi-level morphology control This is the highest efficiency reported in the literature Relevant research results were published in nature commun (nature commun., 2019, 10, 5393) Organic bulk heterojunction (BHJ) solar cells have been widely concerned because of its light weight, low cost and large area flexible preparation With the development of molecular design and the optimization of device technology, the energy conversion efficiency has been greatly improved in recent years In the development of non fullerene system, the efficiency of solar cell based on polymer donor / non fullerene receptor has been increased to more than 17% However, the batch difference of polymer is unavoidable, which restricts its further research and application Therefore, the development of novel small molecule donors based on non fullerene receptors has important scientific significance and application value The crystallinity of small molecules is ideal, and it is easier to produce good phase purity and orderly arrangement, so as to reduce energy loss and improve charge transfer efficiency, and then improve the energy conversion efficiency of organic solar cells However, it is difficult to control the scale of phase separation in all small molecular organic solar cells and form typical interpenetrating network nanostructures in polymer system, which restricts the efficiency of charge separation and transmission in small molecular system and the improvement of filling factor and energy conversion efficiency In order to overcome this problem, we need to start from both molecular design and morphology regulation Wei Zhixiang group selected five membered fused ring dithiopheno benzo dithiophene with good planarity as the core group to construct a-π-d-π-a small molecule donor ZR1, and selected dithiophene as the π bridge to replace the commonly used tritiophene π bridge, in order to reduce the HOMO energy level and increase the molecular rigidity; in the process of active layer morphology optimization, through annealing temperature (110 ℃ - 140 ℃) )The fine control of the multi-level morphology is realized After annealing at 120 ℃, ZR1: y6 device achieves the highest energy conversion efficiency of 14.34% (14.1% certified by China Institute of Metrology) without additives and electron transfer layer The research group successfully obtained the single crystal structure of ZR1 The single crystal X-ray diffraction analysis shows that the molecule has high planarity and rigidity, forming a highly ordered and dense molecular stack The changes of pure film and mixed film before and after annealing were measured by grazing incidence X-ray scattering The results show that ZR1 shows strong molecular stacking after thermal annealing, and the presence of multiple diffraction peaks in the mixed films at 120 ℃ and 140 ℃ indicates the existence of ZR1 crystal According to the results of TEM and resonance soft X-ray analysis, there are large phase size of about 70 nm and small phase size of about 10 nm in the active layer of the blend, and the purity of the phase increases with the increase of temperature This multilevel structure can not only achieve effective charge transfer, but also ensure enough phase separation interface The donor crystal structure of about 100 nm long and 30 nm wide was observed in TEM images At the same time, the results show that ZR1: y6 system has low radiation compound energy loss and non radiation compound energy loss, and the non radiation energy loss is as low as 0.04 V, which is helpful for the improvement of the device open circuit voltage Through donor molecular design and matching with appropriate acceptors, an effective multi-level morphology has been constructed, which can reduce energy loss and improve energy conversion efficiency, deepen the understanding of the molecular design and morphology control of the whole small molecular system, and contribute to the further improvement of the performance of the whole small molecular solar cell This achievement has been supported by national key R & D plan and NSFC.
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