Assessing the energy offset at the electron donor/acceptor interface in organic solar cells through radiative efficiency measurements

Xie, Yuan1; Wang, Weiping2; Huang, Wei3; Lin, Fengyuan3; Li, Tengfei4; Liu, Sha1; Zhan, Xiaowei4; Liang, Yongye3; Gao, Chao2; Wu, Hongbin1; Cao, Yong1

2019

10.1039/c9ee02939g

Energy and Environmental Science   影响因子和分区

17545706

1754-5706

Energy offsets at the electron donor/acceptor interface play an important role in the operation of organic solar cells (OSCs), because their magnitude strongly affects the efficiency of photo-induced charge separation and hence the short-circuit current of a device under illumination. However, quantitative assessment of energy offsets in operating devices remains an open challenge that is still out of the reach of present techniques. Here we show that the ratio of the radiative efficiency (EQEEL) for a blend device to that for the lower bandgap component device (usually a non-fullerene acceptor), namely the EQEEL ratio, can be a strong indicator of the energy offsets in the blend device. In photovoltaic devices based on donors and acceptors with similar backbone structure but varied energy levels, lowering the highest occupied molecular orbital (HOMO) offset increases the open-circuit voltage (VOC) from 0.95 V to 1.05 V, which is consistent with the EQEEL variation trends in the devices. The blend EQEEL approaches that of the emissive low bandgap acceptor when the HOMO of the donor is sufficiently deepened, which at the same time corresponds to a reduction in VOC loss and inefficient photoinduced charge separation. The results suggest that the intrinsic energy loss associated with charge separation can be minimized in practice by minimizing the energy offsets but at the expense of lowering the charge separation efficiency. Statistics from several state-of-the-art material systems reveal that efficient charge generation occurs when the EQEEL ratio is less than 0.1, corresponding to an additional non-radiative voltage loss due to the energy offset of 60 mV. Based on this finding and a modified Shockley-Queisser theory, we estimate an upper thermodynamic efficiency limit for single-junction organic solar cells of about 31%, which is slightly below the Shockley-Queisser limit.
© 2019 The Royal Society of Chemistry.

SCI ; EI

英语

通讯

National Natural Science Foundation of China[51521002] ; National Natural Science Foundation of China[61775061]

Chemistry ; Energy & Fuels ; Engineering ; Environmental Sciences & Ecology

Chemistry, Multidisciplinary ; Energy & Fuels ; Engineering, Chemical ; Environmental Sciences

WOS:000501225900007

Royal Society of Chemistry

20195107872082

Energy dissipation ; Energy gap ; Molecular orbitals ; Open circuit voltage ; Separation

Energy Losses (industrial and residential):525.4 ; Physical Chemistry:801.4 ; Chemical Operations:802.3

Web of Science

1.Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou; 510640, China
2.State Key Laboratory of Fluorine and Nitrogen Chemicals, Xi'An Modern Chemistry Research Institute, Xi'an Shaanxi; 710065, China
3.Department of Materials Science and Engineering, Shenzhen Key Laboratory of Printed Organic Electronics, Southern University of Science and Technology, Shenzhen; 518055, China
4.Department of Materials Science and Engineering, College of Engineering, Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, Peking University, Beijing; 100871, China

Xie, Yuan,Wang, Weiping,Huang, Wei,et al. Assessing the energy offset at the electron donor/acceptor interface in organic solar cells through radiative efficiency measurements[J]. Energy and Environmental Science,2019,12(12):3556-3566.

Xie, Yuan.,Wang, Weiping.,Huang, Wei.,Lin, Fengyuan.,Li, Tengfei.,...&Cao, Yong.(2019).Assessing the energy offset at the electron donor/acceptor interface in organic solar cells through radiative efficiency measurements.Energy and Environmental Science,12(12),3556-3566.

Xie, Yuan,et al."Assessing the energy offset at the electron donor/acceptor interface in organic solar cells through radiative efficiency measurements".Energy and Environmental Science 12.12(2019):3556-3566.