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Impact of Solvent Additive on Carrier Transport in Polymer:Fullerene Bulk Heterojunction Photovoltaic Cells
Author(s) -
Ho Carr Hoi Yi,
Dong Qi,
Yin Hang,
Leung Winky Wing Ki,
Yang Qingdan,
Lee Harrison Ka Hin,
Tsang Sai Wing,
So Shu Kong
Publication year - 2015
Publication title -
advanced materials interfaces
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.671
H-Index - 65
ISSN - 2196-7350
DOI - 10.1002/admi.201500166
Subject(s) - electron mobility , materials science , fullerene , polymer solar cell , electron , acceptor , solvent , heterojunction , limiting , electron transport chain , polymer , analytical chemistry (journal) , chemical physics , optoelectronics , condensed matter physics , organic chemistry , chemistry , composite material , physics , mechanical engineering , biochemistry , quantum mechanics , engineering
The effects of a solvent additive, 1,8‐diiodooctane (DIO), on both hole and electron transport are investigated in a state‐of‐the‐art bulk‐heterojunction (BHJ) system, namely PTB7:PC 71 BM. For a polymer:fullerene weight ratio of 1:1.5, the electron mobility in the blend film increases by two orders of magnitude with the DIO concentration while almost no change is found in the hole mobility. For lower DIO concentrations, the electron mobility is suppressed because of large, but poorly connected PC 71 BM domains. For higher concentrations of DIO, the electron mobility is improved progressively and the hole mobility becomes the limiting factor. Between 1 and 5 vol%, the electron and hole mobilities are balanced. Using the Gaussian disorder model (GDM), we found that the DIO concentration modifies fundamentally the average hopping distances of the electrons. In addition, there exist alternative donor–acceptor ratios to achieve optimized PTB7:PC 71 BM based solar cells. It is demonstrated that the fullerene content of the BHJ film can be significantly reduced from 1:1.5 to 1:1 while the optimized performance can still be preserved.