Non-Fullerene-Derivative-Dependent Dielectric Properties in High-Performance Ternary Organic Solar Cells

Abstract

Ternary blend solar cell, a promising strategy by introducing additional component with either an extra acceptor or an extra donor to a conventional binary blend, improves the performance of the solar cell. However, the mismatch of energy band structure and the tradeoff between open-circuit voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oc</sub> ) and short-circuit current density (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9c</sub> ) can be heavily affected by incorporating an inappropriate third component to the ternary system. In this paper, a non-fullerene acceptor, 5,5'-[(6,12-dihydro-6, 6,12,12-tetraoctylindeno[1,2-b]fluorene-2,8-diyl)bis(2,1,3-benzoth iadiazole-7,4-diylmethylidyne)]bis[3-ethyl-2-thioxo-4-thiazolidino ne (IDFBR) as a third component was introduced into the reference binary poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b'] dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3, 4-b]thiophenediyl] and [6,6]-Phenyl-C71-butyric acid methyl ester solar cells. The best power conversion efficiency for the ternary blend solar cell was achieved when adding 5 wt% of IDFBR. The optimized ternary device exhibited a spectacular improvement of Coulomb capture radius, which is 66% higher than the reference device. This incorporation of IDFBR can effectively adjusted the dielectric constant, reduce the Coulomb capture radius, which suppresses the charge recombination and facilitates the charge transport. As a result, in conjunction with the cascading energy alignment, complementary absorption spectrum, and improved morphology, the optimized ternary device showed a simultaneous enhancement in J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sc</sub> , V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oc</sub> , and fill factor.