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Hierarchical Nanomorphologies Promote Exciton Dissociation in Polymer/Fullerene Bulk Heterojunction Solar Cells



Wei Chen, Tao Xu, Feng He, Wei Wang, Cheng Wang, Joseph Strzalka, Yun Liu, Jianguo Wen, Dean J. Miller, Jihua Chen, Kunlun Hong, Luping Yu, Seth B. Darling


PTB7 semiconducting copolymer comprising thieno[3,4-b]thiophene and benzodithiophene alternating repeat units set a historic record of solar energy conversion efficiency (7.4%) in polymer:fullerene bulk heterojunction (BHJ) solar cells. To further improve solar cell performance, a thorough understanding of structure¿property relationships associated with PTB7:fullerene and related organic photovoltaic (OPV) devices is crucial. Traditionally, OPV active layers are viewed as an interpenetrating network of pure polymers and fullerenes with discrete interfaces. Here we show that the OPV active layer of PTB7:fullerene OPV devices, in fact, involves hierarchical nanomorphologies ranging from several nanometers of crystallites to tens of nanometers of nanocrystallite aggregates in PTB7-rich and fullerene-rich domains, themselves hundreds of nanometers in size. These hierarchical nanomorphologies are coupled to significantly enhanced exciton dissociation, which consequently contribute to photocurrent, indicating that the nanostructural characteristics at multiple length scales is one of the key factors determining the performance of PTB7 copolymer¿and likely most polymer:fullerene systems¿in OPV devices.
Nano Letters


Organic Photovoltaics, Bulk Heterojunction, Hierarchical Nanomorphology, Charge Photogeneration, X-ray Scattering, Device Performance


Chen, W. , Xu, T. , He, F. , Wang, W. , Wang, C. , Strzalka, J. , Liu, Y. , Wen, J. , Miller, D. , Chen, J. , Hong, K. , Yu, L. and Darling, S. (2011), Hierarchical Nanomorphologies Promote Exciton Dissociation in Polymer/Fullerene Bulk Heterojunction Solar Cells, Nano Letters, [online], (Accessed April 18, 2024)
Created August 7, 2011, Updated October 12, 2021