A New Nonfullerene Acceptor with Near Infrared Absorption for High Performance Ternary-Blend Organic Solar Cells with Efficiency over 13

Abstract

A new acceptor-donor-acceptor (A-D-A) type nonfullerene acceptor, 3TT-FIC, which has three fused thieno[3,2-b]thiophene as the central core and difluoro substituted indanone as the end groups, is designed and synthesized. 3TT-FIC exhibits broad and strong absorption with extended onset absorption to 995 nm and a low optical bandgap of 1.25 eV. The binary device based on 3TT-FIC and the polymer PTB7-Th exhibits a power conversion efficiency (PCE) of 12.21% with a high short circuit current density ( J_sc) of 25.89 mA cm^-2. To fine-tune the morphology and make full use of the visible region sunlight, phenyl-C₇₁-butyricacid-methyl ester (PC₇₁BM) is used as the third component to fabricate ternary devices. In contrast to the binary devices, the ternary blend organic solar cells show significantly enhanced EQE ranging from 300 to 700 nm and thus an improved J_sc with a high value of 27.73 mA cm^-2. A high PCE with a value of 13.54% is achieved for the ternary devices, which is one of the highest efficiencies in single junction organic solar cells reported to date. The results provide valuable insight for the ternary devices in which the external quantum efficiency (EQE) induced by the third component is evidently observed and directly contributed to the enhancement of the device efficiency.

Keywords: nonfullerene acceptors; organic solar cells; ternary blends.

Figure 1

Chemical structures of a) 3TT‐FIC nonfullerene acceptor and b) PTB7‐Th donor, c) UV–Vis absorption spectra of PTB7‐Th, PC₇₁BM, and 3TT‐FIC in neat film, d) the device structure.

Figure 2

a) Current density–voltage (J–V) curves of PTB7‐Th:3TT‐FIC based binary device and PTB7‐Th:3TT‐FIC:PC₇₁BM based ternary device under one sun illumination (AM 1.5 G 100 mW cm⁻²). b) EQE spectra of the corresponding devices. c) J _ph versus V _eff and d) light‐intensity (P) dependence of J _sc measurement of the devices.

Figure 3

AFM images for a) PTB7‐Th:3TT‐FIC blend film and b) PTB7‐Th:3TT‐FIC:PC71BM blend film. TEM images for c) TB7‐Th:3TT‐FIC blend film and d) PTB7‐Th:3TT‐FIC:PCBM blend film.

Figure 4

2D GIXD images of the a) binary and b) ternary blend films. c) The out‐of‐plane (black line) and in‐plane (red line) line‐cut profiles.