Visualizing Complex Multi-Length-Scale Morphology in Non-Fullerene Photovoltaics with Nitrogen K-Edge Resonant Soft X-Ray Scattering
ORAL
Abstract
Multi-length-scale morphology in organic photovoltaics (OPVs) and other functional soft materials leads to high complexity, but often dictates functionality. Such mesoscale complexity in OPVs originates from the kinetically trapped nonequilibrium morphology, which determines the device charge generation and transport. Resonant soft x-ray scattering (RSoXS) has been revolutionary on the exploration of OPV morphology in the past decade. However, for non-fullerene OPVs, RSoXS analysis near the carbon K-edge (CK-RSoXS) has been difficult, due to the chemical similarity of materials used in active layers. An innovative approach is provided by nitrogen K-edge RSoXS (NK-RSoXS), utilizing the spatial and orientational contrasts from the cyano groups in the acceptor material, which allows for determination of the phase separation. Of particular importance is that NK-RSoXS, for the first time, clearly visualizes the combined feature sizes in PM6:Y6 blends from crystallization and liquid-liquid demixing, determining optoelectronic properties. NK-RSoXS also reveals that PM6:Y6:Y6-BO ternary blends with reduced phase separation size and enhanced material crystallization can lead to current amplification in devices.
*This work was financially supported by the National Natural Science Foundation of China (NSFC) (Nos. 51973110, 21734009, and 21905102), Beijing National Laboratory for Molecular Sciences (BNLMS201902), the Center of Hydrogen Science (Shanghai Jiao Tong University, China), and Shanghai Science and Technology Commission science and technology innovation action plan (20ZR1426200). RSoXS measurements were done at beamline 11.0.1.2 at the Advanced Light Source at Lawrence Berkeley National Laboratory (LBNL) and computational methods were supported by a User Project at The Molecular Foundry at LBNL. All LBNL efforts were supported by the Office of Science of the U.S. Department of Energy under Contract no. DE-AC02-05CH11231.
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Publication:Wenkai Zhong, Ming Zhang, Guillaume Freychet, Gregory M. Su, Lei Ying, Fei Huang, Yong Cao, Yongming Zhang, Cheng Wang, Feng Liu, Visualizing Complex Multi-Length-Scale Morphology in Non-Fullerene Photovoltaics with Nitrogen K-Edge Resonant Soft X-Ray Scattering, Advanced Materials, 2021, submitted.
