Incorporating a weak acceptor unit into PTB7-Th to tune the open circuit voltage for non-fullerene polymer solar cells. (26th January 2023)

• Record Type: Journal Article
• Authors: Tang, Yuan; Liu, Longfei; Deng, Jiyong; Sun, Penghao; Yan, Dong; Peng, Wenhong; Huang, Xianwei; Xiao, Manjun; Tao, Qiang; Yu, Donghong
• Is Part Of: Tetrahedron. Volume 131(2023)
• Publication Date: 2023-01-26
• Subjects: Polymer donors -- PTB7-Th -- Weak acceptor unit -- Open circuit voltage -- Non-fullerene polymer solar cells; Chemistry, Organic -- Periodicals; 547.005
• DOI: 10.1016/j.tet.2022.133214
• Languages: English
• ISSNs: 0040-4020

Abstract

Abstract: PTB7-Th is one of the most effective polymer donors which have drawn huge attention in organic solar cells. However, the highest occupied molecular orbital (HOMO) level of PTB7-Th is relatively high, which limit open circuit voltage ( V oc ) of the cell devices. In this work, to develop the new members of PTB7-Th family materials with higher V oc s, two new random terpolymers PTB7-Th(0.9) and PTB7-Th(0.8) have been synthesized, in which contains 10% or 20% benzo[1, 2-b:4, 5-b′]dithiophene-2, 6-dicarboxylate (VBDTC, a weak acceptor unit) moiety in PTB7-Th. It was found that the incorporating of VBDTC unit has great influence on optical and electronic properties of the related polymers. Comparison with PTB7-Th, the PTB7-Th(0.9) and PTB7-Th(0.8) exhibit blue shift in the UV−visible spectra, which forming a more complementary absorption with the low band gap non-fullerene acceptors, like ITIC and Y6. Increasing the percentage of VBDTC moiety, it can sufficiently deepen the low-lying HOMO level of the related polymers, which would expect to an enhancement in V oc . Non-fullerene solar cells blended with ITIC, PTB7-Th(0.9) exhibited a V oc of 0.839 V, with power conversion efficiency (PCE) of 4.86%. Interestingly, PTB7-Th(0.8) showed superior photovoltaic performance with a V oc of 0.862 V, and PCE of 5.24%. And when blended with Y6, the PCE of PTB7-Th(0.8) based device was further improved to 6.13%, due to increasing the short-circuit current ( J sc ). The comprehensive study reveals that it is an effective strategy to tune the absorption spectra and deepens the HOMO energy level of the PTB7-Th related polymers by incorporation of a weak acceptor unit, thus, achieving higher V oc as well as photovoltaic performance. Graphical abstract: To develop the new members of PTB7-Th family materials with higher V oc s, two new random terpolymers PTB7-Th(0.9) and PTB7-Th(0.8) were synthesized. Comparison with PTB7-Th, the two terpolymers based non-fullerene (PSCs) displayed significantly enhanced V oc from 0.81 to 0.86 V, due to their deeper HOMO levels. A PCE of 6.13% was obtained in PTB7-Th(0.8) based device. Image 1