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Understanding the Critical Role of Sequential Fluorination of Phenylene Units on the Properties of Dicarboxylate Bithiophene‐Based Wide‐Bandgap Polymer Donors for Non‐Fullerene Organic Solar Cells
Author(s) -
Kini Gururaj P.,
Lee Eui Jin,
Jeon Sung Jae,
Moon Doo Kyung
Publication year - 2021
Publication title -
macromolecular rapid communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 154
eISSN - 1521-3927
pISSN - 1022-1336
DOI - 10.1002/marc.202000743
Subject(s) - coplanarity , organic solar cell , materials science , band gap , fullerene , polymer , phenylene , acceptor , energy conversion efficiency , fluorine , photovoltaics , polymer chemistry , chemical engineering , photochemistry , optoelectronics , organic chemistry , chemistry , photovoltaic system , composite material , ecology , geometry , mathematics , physics , engineering , metallurgy , biology , condensed matter physics
Design and development of wide bandgap (WBG) polymer donors with low‐lying highest occupied molecular orbitals (HOMOs) are increasingly gaining attention in non‐fullerene organic photovoltaics since such donors can synergistically enhance power conversion efficiency (PCE) by simultaneously minimizing photon energy loss ( E loss ) and enhancing the spectral response. In this contribution, three new WBG polymer donors, P1, P2, and P3, are prepared by adding phenylene cores with a different number of fluorine (F) substituents ( n = 0, 2, and 4, respectively) to dicarboxylate bithiophene‐based acceptor units. As predicted, fluorination effectively aides in the lowering of HOMO energy levels, tailoring of the coplanarity and molecular ordering in the polymers. Thus, fluorinated P2 and P3 polymers show higher coplanarity and more intense interchain aggregation than P1, leading to higher charge carrier mobilities and superior phase‐separated morphology in the optimized blend films with IT‐4F. As a result, both P2:IT‐4F and P3:IT‐4F realize the best PCEs of 6.89% and 7.03% (vs 0.16% for P1:IT‐4F) with lower E loss values of 0.65 and 0.55 eV, respectively. These results signify the importance of using phenylene units with sequential fluorination in polymer backbone for modifying the optoelectronic properties and realizing low E loss values by synergistically lowering the HOMO energy levels.