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Photocurrent Enhancement in Diketopyrrolopyrrole Solar Cells by Manipulating Dipolar Anchoring Terminals on Alkyl‐Chain Spacers
Author(s) -
Tang Ailing,
Lu Zhenhuan,
Bai Shuming,
Huang Jianhua,
Chen Yuxia,
Shi Qiang,
Zhan Chuanlang,
Yao Jiannian
Publication year - 2014
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201301416
Subject(s) - anchoring , photocurrent , alkyl , stacking , materials science , side chain , dipole , crystallography , stereochemistry , chemistry , optoelectronics , polymer , organic chemistry , structural engineering , engineering , composite material
We chose DPP‐BDT‐DPP {DPP=diketopyrrolopyrrole, BDT=4,8‐di‐[2‐(2‐ethylhexyl)‐thienyl]benzo[1,2‐ b :4,5‐ b ′]dithiophene} as a model backbone and varied the anchoring groups [C 5 H 11 , COOCH 3 , and SiCH 3 (OSiCH 3 ) 2 ] terminated on the N‐substituted alkyl‐chain spacer of the DPP units to study the effect of anchoring terminals on the morphology of blend film and on the device performances of bulk heterojunction solar cells. By replacing the nonpolar C 5 H 11 anchoring terminal with the polar COOCH 3 anchoring terminal leads to an enhancement in the short‐circuit current density ( J sc ) (4.62 vs. 9.32 mA cm −2 ), whereas the value of J sc sharply decreases to 0.45 mA cm −2 if the C 5 H 11 anchoring terminal is replaced by a SiCH 3 (OSiCH 3 ) 2 group. The changes in J sc are associated with changes in the π–π stacking distance (3.39→3.34 Å vs. 3.39→3.45 Å) and the phase size (50→20 nm vs. 50→>250 nm) through alteration of the anchoring group from C 5 H 11 to COOCH 3 versus from C 5 H 11 to SiCH 3 (OSiCH 3 ) 2 . Interestingly, the anchoring terminals bring about drastic changes in molecular orientations, which result in different out‐of‐plane hole transport. This is the first time this effect has been systemically demonstrated to improve photocurrent generation by manipulating the dipolar anchoring groups terminated on the alkyl‐chain spacer.