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Enhanced Photovoltaic Performance of Amorphous Donor–Acceptor Copolymers Based on Fluorine‐Substituted Benzodioxocyclohexene‐Annelated Thiophene
Author(s) -
Ie Yutaka,
Morikawa Koki,
Zajaczkowski Wojciech,
Pisula Wojciech,
Kotadiya Naresh B.,
Wetzelaer GertJan A. H.,
Blom Paul W. M.,
Aso Yoshio
Publication year - 2018
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201702506
Subject(s) - materials science , amorphous solid , copolymer , polymer solar cell , organic solar cell , thiophene , acceptor , electron mobility , conjugated system , homo/lumo , energy conversion efficiency , chemical engineering , polymer chemistry , organic chemistry , optoelectronics , polymer , chemistry , molecule , composite material , physics , engineering , condensed matter physics
Donor–acceptor (D‐A) type π‐conjugated copolymers with crystalline behavior have been extensively investigated as donor semiconductors in organic photovoltaics (OPVs). On the other hand, the development of high‐performance amorphous donor materials is still behind. The amorphous donor copolymer DTS‐C 0 (F 2 ) consisting of dithieno[3,2‐ b :2′,3′‐ d ]silole ( DTS ) donor unit and the recently developed fluorine‐substituted naphtho[2,3‐ c ]thiophene‐4,9‐dione ( C 0 (F 2 ) ) acceptor unit shows moderate photovoltaic performance upon blending with PC 71 BM. In this work, to enhance the hole‐transporting characteristics, a 3‐hexylthiophene ( HT ) spacer unit is integrated into the conjugated backbone, resulting in a new amorphous copolymer DTS‐HT‐C 0 (F 2 ) . The strong electron‐accepting nature of C 0 (F 2 ) allows the introduction of the HT spacer without affecting the frontier orbital energies and thus the D‐A character. Without using solvent additives and thermal annealing, OPVs based on DTS‐HT‐C 0 (F 2 ) and [6,6]‐phenyl‐C71‐butyric acid methyl ester PC 71 BM show an improved power conversion efficiency of 9.12%. Investigation of the device physics unambiguously reveals that the hole mobility of the copolymer in the blend is increased by an order of magnitude by the introduction of HT , while keeping an amorphous film nature, leading to higher short‐circuit current density and fill factor. These results demonstrate the realization of high‐performance OPVs based on amorphous active layers.