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Mobility Relaxation of Holes and Electrons in Polymer:Fullerene and Polymer : Non‐Fullerene Acceptor Solar Cells
Author(s) -
Hamada Fumiya,
Saeki Akinori
Publication year - 2021
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.202100566
Subject(s) - fullerene , materials science , acceptor , relaxation (psychology) , electron mobility , polymer , organic solar cell , band gap , polymer solar cell , conjugated system , electron acceptor , charge carrier , chemical physics , electron , photochemistry , organic chemistry , optoelectronics , chemistry , condensed matter physics , composite material , physics , quantum mechanics , psychology , social psychology
A non‐fullerene small molecular acceptor (NFA) is a prominent molecule that shows moderate electron mobility and a narrow bandgap complementary to middle‐bandgap p‐type conjugated polymers, which leads to great improvement in the performance of organic photovoltaic (OPV) cells. However, little is known about the relaxation of charge carriers, which is key to efficient charge transport. Simultaneous time‐of‐flight (TOF) and time‐resolved microwave conductivity (TRMC) measurements have been carried out on benzodithiophene‐based polymer (PBDB‐T):soluble C 70 ‐fullerere (PCBM) and PBDB‐T:NFA (ITIC or Y6) blends, as benchmark systems. In addition to the conventional TOF mobilities, relaxation of the hole and electron mobility are evaluated by TRMC under an external electric field. PBDB‐T : ITIC exhibits much faster relaxation than PBDB‐T : PCBM, whereas that in PBDB‐T : Y6 is moderate. This is consistent with the energetic disorder estimated from the photoabsorption onset. Interestingly, the slower relaxation of the electrons compared to the holes in PBDB‐T : Y6 is in line with the preferred normal device structure. Our work deepens the understanding of the energetics of polymer : NFA blends and offers a basis for achieving efficient NFA properties.