Zhan Lingling, Li Shuixing, Zhang Shuhua, Chen Xingzhi, Lau Tsz-Ki, Lu Xinhui, Shi Minmin, Li Chang-Zhi, Chen Hongzheng
MOE Key Laboratory of Macromolecular Synthesis and Functionalization, State Key Laboratory of Silicon Materials, Department of Polymer Science and Engineering , Zhejiang University , Hangzhou 310027 , P. R. China.
Department of Physics , Chinese University of Hong Kong , New Territories , Hong Kong 999077 , P. R. China.
ACS Appl Mater Interfaces. 2018 Dec 12;10(49):42444-42452. doi: 10.1021/acsami.8b16131. Epub 2018 Nov 30.
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-C-butyric acid methyl ester (PCBM) 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. PCBM 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/PCBM and PBDB-TF/HC-PCIC/PCBM 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.
驱动力不足被定义为给体和受体之间前沿分子轨道的能量偏移，这会影响有机太阳能电池（OSC）中的电荷分离，从而限制了量子效率的提高。在此，我们证明通过三元策略增强富勒烯与非富勒烯受体之间的电荷转移是解决这一问题的有效方法。通过将电子受体[6,6]-苯基-C-丁酸甲酯（PCBM）作为第三组分引入基于聚[(2,6-(4,8-双(5-(2-乙基己基)-4-氟噻吩-2-基)-苯并[1,2-b:4,5-b']二噻吩))-alt-(5,5-(1',3'-二-2-噻吩基-5',7'-双(2-乙基己基)苯并[1',2'-c:4',5'-c']二噻吩-4,8-二酮)]（PBDB-TF）的聚合物给体以及具有未稠合核的小分子受体2,2'-((2Z,2'Z)-(((2,5-二氟-1,4-亚苯基)双(4,4-双(2-乙基己基)-4H-环戊并[2,1-b:3,4-b']二噻吩-6,2-二基))双(亚甲基))双(5,6-二氟-3-氧代-2,3-二氢-1H-茚-2,1-二亚基))二丙二腈（HF-PCIC）或2,2'-((2Z,2'Z)-(((2,5-二氟-1,4-亚苯基)双(4,4-双(2-乙基己基)-4H-环戊并[2,1-b:3,4-b']二噻吩-6,2-二基))双(亚甲基))双(5,6-二氯-3-氧代-2,3-二氢-1H-茚-2,1-二亚基))二丙二腈（HC-PCIC）的二元共混物中，在较长波长范围内，量子效率可从二元共混物的约70%提高到三元共混物的80%以上。PCBM显示出较低的能级和较高的电子迁移率，有利于三元OSC中的电荷转移和传输，从而提高了量子效率。结果，基于PBDB-TF/HF-PCIC/PCBM和PBDB-TF/HC-PCIC/PCBM的三元OSC分别表现出11.55%和12.36%的高功率转换效率（PCE）。此外，两种三元OSC都实现了优异的热稳定性，在130℃热处理12小时后保留了约80%的初始PCE，这表明含有富勒烯/非富勒烯受体的活性层形态得到了稳定。这项工作展示了通过能级调制实现富勒烯与非富勒烯受体之间电荷转移增强的高效且热稳定的三元OSC，这有助于更好地理解三元OSC的工作机制。
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