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Enhanced Charge Transfer Between Fullerene and Non-Fullerene Acceptors Enables Highly Efficient Ternary Organic Solar Cells

Lingling Zhan, Shuixing Li, Shuhua Zhang, Xingzhi Chen, Tsz-Ki Lau, Xinhui Lu, Minmin Shi, Chang-Zhi Li, Hongzheng Chen

ACS Appl Mater Interfaces. 2018 Dec 12;10(49):42444-42452.

PMID: 30444596

Abstract:

Insufficient driving forces defined as the energetic offsets of the frontier molecular orbitals between a donor and an acceptor influence the charge separation in organic solar cells (OSCs), thus restricting the improvement of quantum efficiencies. Herein, we demonstrate that enhancing charge transfer between fullerene and non-fullerene acceptors via ternary strategy is an effective method to address this problem. By introducing an electron acceptor [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as the third component to the binary blends based on the polymer donor of poly[(2,6-(4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)-benzo[1,2- b:4,5- b']dithiophene))- alt-(5,5-(1',3'-di-2-thienyl-5',7'-bis(2-ethylhexyl)benzo[1',2'- c:4',5'- c']dithiophene-4,8-dione)] (PBDB-TF) and the small-molecule acceptor of 2,2'-((2 Z,2' Z)-(((2,5-difluoro-1,4-phenylene)bis(4,4-bis(2-ethylhexyl)-4 H-cyclopenta[2,1- b:3,4- b']dithiophene-6,2-diyl))bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1 H-indene-2,1-diylidene))dimalononitrile (HF-PCIC) or 2,2'-((2 Z,2' Z)-(((2,5-difluoro-1,4-phenylene)bis(4,4-bis(2-ethylhexyl)-4 H-cyclopenta[2,1- b:3,4- b']dithiophene-6,2-diyl))bis(methanylylidene))bis(5,6-dichloro-3-oxo-2,3-dihydro-1 H-indene-2,1-diylidene))dimalononitrile (HC-PCIC) with unfused cores, the quantum efficiencies can be boosted from ∼70% for binary blends to over 80% for ternary blends in the longer wavelength ranges. PC71BM shows lower energy levels and higher electron mobility, benefiting the charge transfer and transport in ternary OSCs and resulting in an enhanced quantum efficiency. As a result, ternary OSCs based on PBDB-TF/HF-PCIC/PC71BM and PBDB-TF/HC-PCIC/PC71BM exhibit high power conversion efficiencies (PCEs) of 11.55 and 12.36%, respectively. In addition, excellent thermal stabilities are realized for both ternary OSCs, which retained ∼80% initial PCEs after thermal treatment at 130 °C for 12 h, indicating that the active layer morphology containing fullerene/non-fullerene acceptors is stabilized. This work demonstrates efficient and thermally stable ternary OSCs with enhanced charge transfer between fullerene and non-fullerene acceptors via the modulation of energy levels, which helps to better understand the working mechanism of ternary OSCs.

Chemicals Related in the Paper:

Catalog Number Product Name Structure CAS Number Price
AP1134942203 2,6-Ditolylbenzo[1,2-b:4,5-b′]dithiophene 2,6-Ditolylbenzo[1,2-b:4,5-b′]dithiophene 1134942-20-3 Price
AP32281360 Benzo[1,2-b:4,5-b']dithiophene-4,8-dione Benzo[1,2-b:4,5-b']dithiophene-4,8-dione 32281-36-0 Price
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