Abstract
Facile synthesis of an interfacial layer in organic solar cells (OSCs) is important for broadening material designs and upscaling photovoltaic conversion efficiency (PCE). Herein, a mild solution process of spin-coating In(acac)3 and Ga(acac)3 isopropanol precursors followed by low-temperature thermal treatment was developed to fabricate In2O3 and Ga2O3 cathode buffer layers (CBLs). The introduction of In2O3 or Ga2O3 CBLs endows PM6:Y6-based OSCs with outstanding performance and high PCEs of 16.17% and 16.01%, respectively. Comparison studies present that the In2O3 layer possesses a work function (WF) of 4.58 eV, which is more favorable for the formation of ohmic contact compared with the Ga2O3 layer with a WF of 5.06 eV and leads to a higher open circuit voltage for the former devices. Electrochemical impedance spectroscopy was performed to reveal how In2O3 and Ga2O3 affect the internal charge transfer and the origin of their performance difference. Although In2O3 possesses lower series resistance loss, Ga2O3 has a higher recombination resistance, which enhances the device fill factor and compensates for its series resistance loss to some extent. Comparative analysis of the photo-physics of In2O3 and Ga2O3 suggests that both are excellent CBLs for highly efficient OSCs.
摘要
有机太阳电池(OSCs)中, 温和的界面材料制备工艺对于拓宽 材料适用范围和提高器件能量转换效率(PCE)具有重要作用. 本文 提出了简便易行的In2O3和Ga2O3电子收集层的制备方法, 即旋涂 In(acac)3和Ga(acac)3异丙醇前驱体溶液并结合低温热退火. 在基于 PM6:Y6的OSCs中引入In2O3和Ga2O3电子收集层, 得到了性能优异 的器件, PCE分别达到16.17和16.01. 对比研究发现, In2O3的功函数 WF为4.58 eV, 这比WF为5.06 eV的Ga2O3更有利于与ITO电极形成 欧姆接触, 因此基于前者的器件开路电压更高. 此外, 电化学阻抗谱 EIS的研究进一步揭示了In2O3和Ga2O3对器件内部电荷转移过程的 影响及其性能差异的由来: In2O3的串联电阻损耗虽然较低, 但 Ga2O3的复合电阻较高, 所以一定程度上提高了基于Ga2O3的器件 的填充因子, 进而补偿了其串联电阻的损失. 本论文的对比研究发 现, In2O3和Ga2O3都是OSCs优异的电子收集层.
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Acknowledgements
This work was supported by the National Natural Science Foundation of China (51573042, 61874148, 51873007, 5181101540 and 21835006), the Fundamental Research Funds for the Central Universities in China (2019MS025 and 2018MS032), and the State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources (LAPS20003).
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Bai YM and Tan Z designed the electron collection layers, performed the data analysis and wrote the paper; Shi R performed part of the experiments, figures and data analyses; Bai YL performed some data analysis; Wang F and Wang J contributed to the theoretical analysis. All authors contributed to the general discussion.
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Yiming Bai is an associate professor at the State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University (NCEPU). She obtained PhD from the Institute of Semiconductor, Chinese Academy of Sciences (CAS) in 2007, and then worked in the Key Laboratory of Semiconductors, CAS. In Nov. 2009, she joined the Renewable Energy School, NCEPU. Her research interests concentrate on photovoltaic materials and devices.
Zhan’ao Tan has been a professor in Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology since 2018, and he worked as a professor in NCEPU from 2009 to 2019. Currently, he leads the Group of Organic Optoelectronic Materials and Devices. His present research interests include organic solar cells, colloidal nanocrystal and carbon dots-based optoelectronics, perovskite solar cells and light-emitting diodes.
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Bai, Y., Shi, R., Bai, Y. et al. Efficient organic solar cells with low-temperature in situ prepared Ga2O3 or In2O3 electron collection layers. Sci. China Mater. 64, 1095–1104 (2021). https://doi.org/10.1007/s40843-020-1514-3
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DOI: https://doi.org/10.1007/s40843-020-1514-3