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Enhancement in Organic Photovoltaic Efficiency through the Synergistic Interplay of Molecular Donor Hydrogen Bonding and π‐Stacking
Author(s) -
Shewmon Nathan T.,
Watkins Davita L.,
Galindo Johan F.,
Zerdan Raghida Bou,
Chen Jihua,
Keum Jong,
Roitberg Adrian E.,
Xue Jiangeng,
Castellano Ronald K.
Publication year - 2015
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201501815
Subject(s) - materials science , stacking , chromophore , organic solar cell , polymer solar cell , energy conversion efficiency , photocurrent , chemical physics , hydrogen bond , acceptor , organic semiconductor , nanotechnology , photochemistry , optoelectronics , molecule , polymer , organic chemistry , chemistry , physics , composite material , condensed matter physics
For organic photovoltaic (OPV) cells based on the bulk heterojunction (BHJ) structure, it remains challenging to rationally control the degree of phase separation and percolation within blends of donors and acceptors to secure optimal charge separation and transport. Reported is a bottom‐up, supramolecular approach to BHJ OPVs wherein tailored hydrogen bonding (H‐bonding) interactions between π‐conjugated electron donor molecules encourage formation of vertically aligned donor π‐stacks while simultaneously suppressing lateral aggregation; the programmed arrangement facilitates fine mixing with fullerene acceptors and efficient charge transport. The approach is illustrated using conventional linear or branched quaterthiophene donor chromophores outfitted with terminal functional groups that are either capable or incapable of self‐complementary H‐bonding. When applied to OPVs, the H‐bond capable donors yield a twofold enhancement in power conversion efficiency relative to the comparator systems, with a maximum external quantum efficiency of 64%. H‐bond promoted assembly results in redshifted absorption (in neat films and donor:C 60 blends) and enhanced charge collection efficiency despite disparate donor chromophore structure. Both features positively impact photocurrent and fill factor in OPV devices. Film structural characterization by atomic force microscopy, transmission electron microscopy, and grazing incidence wide angle X‐ray scattering reveals a synergistic interplay of lateral H‐bonding interactions and vertical π‐stacking for directing the favorable morphology of the BHJ.