In the three-phase (pure donor, pure acceptor, and mixed phases) morphologies of organic solar cells, the mixed phases produce an energy cascade that promotes the generation of free carriers. However, how to optimize the content of the mixed phases is a challenging problem. The authors proposed to control different content of mixed phases in DRTB-T and IDIC blends by additive and solvent vapor annealing (SVA). The authors first formed the largest extent amount of mixed phases by the additive cinene (2%) to inhibit the crystallization of DRTB-T and IDIC. And then, different amounts of mixed phases were achieved by further SVA for different times (from 0 to 50 s) to increase the content of pure DRTB-T and IDIC phases. The energetic offsets (ΔE) of pure and mixed phases gradually decrease from 0.529 to 0.477 eV for different content of mixed phases. When ΔE was 0.498 eV, the highest photocurrent density (Jsc) was obtained. The power conversion efficiency was increased from 3.23% (without any treatment) to 8.54%. Therefore, the authors demonstrated that the optimized content of the mixed phases is critical to device performance.
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This work was supported by the National Natural Science Foundation of China (51890871, 91833306, and 51573185). W.M. thanks for the support from the Ministry of Science and Technology (No. 2016YFA0200700), NSFC (21875182), and 111 Projects 2.0 (BP2018008). X-ray data were acquired at beamlines 7.3.3 and 18.104.22.168 at the Advanced Light Source, which is supported by the Director, Office of Science, Office of Basic Energy Sciences, the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The authors thank Chenhui Zhu at beamline 7.3.3 and Cheng Wang at beamline 22.214.171.124 for assistance with data acquisition.
The supplementary material for this article can be found at u]https://doi.org/10.1557/mrc.2019.139.
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Yi, Y., Gao, X., Yuan, J. et al. Optimized mixed phases to achieve improved performance of organic solar cells. MRS Communications 9, 1235–1241 (2019). https://doi.org/10.1557/mrc.2019.139