Double-hydrogen-bond solid additives to improve morphology, efficiency and stability of fullerene OSCs

Abstract

Active layer morphology of organic solar cells (OSCs) is crucial to improve device properties. In this work, a strategy of solid additives in active layer is proposed to inhibit the adverse effects of DIO, improve morphology and power conversion efficiency (PCE) in fullerene OSCs. For this purpose, a novel type of solid additives with double-hydrogen-bond (2H-bond) character was primarily designed and synthesized. These 2H-bond solid additives are 2H-TR, 2H-TC6R, 2H-TCi8R and 2H-TOC8R, which contain two rhodanine terminal groups and a substituted thiophene core. The effect of the added 2H-bond solid additives on absorption and morphology of photoactive layer, as well as PCE and stability of fullerene OSCs was studied. In the PTB7-Th/PC60BM/3.0 wt% DIO blend system, it is found that the absorption was enhanced and morphology was improved while a few 2H-bond solid additives were added, especially after heating at 100 °C for 120 min. As a result, the PTB7-Th/PC60BM/3.0 wt% DIO-based devices further exhibited a significantly increasing stability and an improved PCE of 7.18% processed by 1.0 wt% 2H-TOC8R. Here, the stability is promoted from 0 to 120 min at 100 °C and the PCE value is increased by 19.3% in comparison to that in the original devices without any process. This work indicates that 2H-bond solid additives are promising additives used to achieve high-performance and stability fullerene OSCs.