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Pronounced Dependence of All‐Polymer Solar Cells Photovoltaic Performance on the Alkyl Substituent Patterns in Large Bandgap Polymer Donors
Author(s) -
Chen Jiale,
Huang Xuelong,
Cao Zhixiong,
Liu Shengjian,
Liang Kexin,
Liu Jinhai,
Jiao Xuechen,
Zhao Jiaji,
Li Qingduan,
Cai YuePeng
Publication year - 2020
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.202000176
Subject(s) - alkyl , polymer , substituent , materials science , conjugated system , side chain , polymer solar cell , band gap , polymer chemistry , chemistry , photochemistry , organic chemistry , optoelectronics , composite material
Abstract For all‐polymer solar cells which are composed of polymer donors and polymer acceptors, the effect of alkyl side chains on photovoltaic performance is a matter of some debate, and this effect remains difficult to forecast. In this concise contribution, we demonstrate that three alkyls namely branched alkyl 2‐butyloctyl (2BO), long linear alkyl n‐dodecyl (C12), and double‐short linear alkyl n‐hexyls (DC6) incorporated into the side chains of large bandgap polymer donor PBDT‐TTz can induce considerable, of significance, and different electronic, optical, and morphological parameters. Systematic studies shed light on the critical role of the double‐short linear alkyl n‐hexyls (DC6) in (i) producing large ionization potential value, (ii) increasing propensity of the polymer to order along the π‐stacking direction, (iii) generating polymer crystallites with more preferential “face‐on” orientation, consequently, (iv) improvement of carriers transportation, (v) suppression of charge recombination, (vi) reduction of energy loss in all‐polymer devices. In parallel, we unearth that the PBDT‐TTz with double‐short linear alkyl n‐hexyls (DC6) represents the highest efficiency of 8.3 %, whereas, the other two PBDT‐TTz analogues (2BO, C12) yield efficiencies of less than 3 % in optimized all‐polymer solar cells. Though branched or long linear alkyl side chains (2BO, C12) have been applied to provide the solution processability of conjugated polymers, motifs bearing multiple short linear alkyl substituents (DC6) are proved critical to the development of high performing polymers.