A novel AH-D-A-type phase junction material to improve photovoltaic performance and device stability in fullerene OSCs

In order to boost power conversion efficiency (PCE) and operation stability of organic solar cells (OSCs), we propose a new idea of phase junction materials (PJMs) used as a photoactive layer component to improve device performance and stability. For this purpose, a novel PJM of H-TRC8 based on rhodanine unit was designed with a conjugated A_H-D-A framework. Here, A_H is a hydrogen-donating electron acceptor unit, D-A is an electron donor-acceptor unit. It is found that H-TRC8 has a good carrier-transporting ability, as well as definite hydrogen-bond and D-A interaction with donor/acceptor materials. While H-TRC8 is added into the PBDB-T/PC₆₀BM blend film with 1.0 vol% DIO (1,8-diiodooctane), the resulting blend film exhibited an enhanced absorption and improved morphology. The intermolecular hydrogen bond between H-TRC8 and PBDB-T plays an important role for them, which is confirmed via FT-IR spectra and 2D ¹H NMR. As a result, the PBDB-T/PC₆₀BM-based devices with 1.25 wt% H-TRC8 and 1.0 vol% DIO exhibit a significantly improved PCE of 8.06%, which is increased by 20.6% in comparison to that in the binary devices with 1.0 vol% DIO only (PCE = 6.68%). Furthermore, the device stability is significantly enhanced with only 43% PCE roll-off at 150 °C for 120 h. This work indicates that A_H-D-A-type PJMs are promising photovoltaic materials used as photoactive-layer components to achieve high-performance fullerene OSCs with high device stability.