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Branched 2‐Ethylhexyl Substituted Indacenodithieno[3,2‐b]Thiophene Core Enabling Wide‐Bandgap Small Molecule for Fullerene‐Based Organic Solar Cells with 9.15% Efficiency: Effect of Length and Position of Fused Polycyclic Aromatic Units
Author(s) -
Wang JinLiang,
Zhang HanJian,
Liu Sha,
Liu KaiKai,
Liu Feng,
Wu HongBin,
Cao Yong
Publication year - 2018
Publication title -
solar rrl
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.544
H-Index - 37
ISSN - 2367-198X
DOI - 10.1002/solr.201800108
Subject(s) - thiophene , materials science , band gap , energy conversion efficiency , organic solar cell , fullerene , homo/lumo , conjugated system , optoelectronics , molecule , chemistry , polymer , organic chemistry , composite material
A pair of 2‐ethylhexyl‐substituted indacenodithieno[3,2‐b]thiophene ( EH‐IDTT ) based tetrafluorinated substituted wide‐bandgap small molecular donor materials with different electron‐rich terminal units, DT4FIDTT and TT4FIDTT , has been synthesized for high efficiency fullerene‐based organic solar cells. The utilization of the EH‐IDTT center core increased the optical bandgap of DT4FIDTT ( E g of 1.86 eV) and decreased HOMO energy level in thin films in comparison with those of BIT‐4F‐T with indacenodithiophene core and thiophene π bridge. Compared to DT4FIDTT with 2,2′‐bithiophene terminal unit, TT4FIDTT with further fused thieno[3,2‐b]thiophene terminal units exhibited a larger optical bandgap and more straight conformation due to less effective conjugated length of thieno[3,2‐b]thiophene. Devices based on DT4FIDTT / PC 71 BM exhibited high power conversion efficiency (PCE) up to 9.15%, significantly higher than that of the device based on TT4FIDTT / PC 71 BM (PCE of 7.35%). The higher J sc of the device based on DT4FIDTT / PC 71 BM can be attributed to its better charge transport properties and favorable phase separation features. Such high efficiency of 9.15% is the highest value reported for the fullerene‐based organic solar cells based on wide‐bandgap ( E g > 1.85 eV) small molecular donor, demonstrating the feasibility of branched alkylated‐indacenodithieno[3,2‐b]thiophene core in enhancing overall photovoltaic performance.