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

Journal Article · Sat Jan 01 00:00:00 EST 2011 · Nano Letters

DOI:https://doi.org/10.1021/nl201715q· OSTI ID:1038470

Chen, Wei ^[1]; Xu, Tao ^[2]; He, Feng ^[2]; Wang, Wei ^[2]; Wang, Cheng ^[3]; Strzalka, Joseph ^[1]; Liu, Yun ^[4]; Wen, Jianguo ^[1]; Miller, Dean ^[1]; Chen, Jihua ^[5]; Hong, Kunlun ^[5]; Yu, Luping ^[2]; Darling, Seth B. ^[1]

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1. Argonne National Laboratory (ANL)
2. University of Chicago
3. Lawrence Berkeley National Laboratory (LBNL)
4. NIST Center for Neutron Research (NCRN), Gaithersburg, MD
5. ORNL

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 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 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.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 1038470
• Journal Information: Nano Letters, Vol. 11, Issue 9; ISSN 1530-6984
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
COPOLYMERS
DISSOCIATION
EFFICIENCY
EXCITONS
FULLERENES
HETEROJUNCTIONS
PERFORMANCE
POLYMERS
SCATTERING
SOLAR CELLS
SOLAR ENERGY CONVERSION