Carboxylate substitution position influencing polymer properties and enabling non-fullerene organic solar cells with high open circuit voltage and low voltage loss

To minimize the voltage loss of non-fullerene organic solar cells (OSCs), it is important to modulate the energy levels of active materials and thus the photovoltage of the device. In this paper, we report a simple and effective approach to tune the energy levels of a state-of-the-art polymer P3TEA...

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Published in:Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2018, Vol.6 (35), p.16874-16881
Main Authors: Liu, Jing, Ma, Lik-Kuen, Sheong, Fu Kit, Zhang, Lin, Hu, Huawei, Zhang, Jing-Xuan, Zhang, Jianquan, Li, Zhengke, Ma, Chao, Han, Xu, Pan, Ding, Ade, Harald, Ma, Wei, Yan, He
Format: Article
Language:English
Subjects:
Electron mobility
Energy conversion efficiency
Energy levels
Fullerenes
Low voltage
Molecular orbitals
Open circuit voltage
Organic chemistry
Photovoltaic cells
Polymers
Quantum efficiency
Solar cells
Solar power
Voltage
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Summary:To minimize the voltage loss of non-fullerene organic solar cells (OSCs), it is important to modulate the energy levels of active materials and thus the photovoltage of the device. In this paper, we report a simple and effective approach to tune the energy levels of a state-of-the-art polymer P3TEA by switching the position of alkyl side chains and carboxylate substituents on the polymer backbone. The resulting polymer P3TAE exhibits a deep highest occupied molecular orbital (HOMO) level, contributing to a high open circuit voltage ( V OC ) of 1.20 V and a small voltage loss of 0.54 V when it is blended with a small molecule acceptor (SMA) FTTB-PDI4. Despite a small charge separation driving force, the P3TAE:FTTB-PDI4 blend exhibits efficient charge extraction, supported by relatively high external quantum efficiency (EQE) (∼60%) in the corresponding device. In addition, the P3TAE:FTTB-PDI4 blend shows relatively high electron mobility and domain purity, leading to a high fill factor (FF) in the device. As a result, the P3TAE:FTTB-PDI4-based solar cell exhibits a power conversion efficiency (PCE) of 8.10%, which is one of the highest achieved performances for single-junction OSCs with V OC higher than 1.20 V. A novel polymer P3TAE enables a high V OC of 1.20 V and a PCE of 8.10% for non-fullerene OSCs.
ISSN:2050-7488
2050-7496
DOI:10.1039/c8ta04935a