Realizing the efficiency-stability balance for all-polymer photovoltaic blends

Abstract

Although the power conversion efficiency (PCE) of organic solar cells (OSCs) has been increased to over 19% under 1 sun illumination, stability is still a shortcoming which impedes commercialization; this has motivated researchers to pay more attention to this issue. Herein we report two types of all-polymer blends: a traditional donor–acceptor pair of PM6:PY-IT; and a one-pot synthesized, multicomponent example called PM6-b-PY-IT, and these exhibit different performance changes under external stress. The PM6-b-PY-IT device has a PCE of 13.63% which is lower than that of 15.24% for PM6:PY-IT, but it has better operational stability under continuous illumination and better thermostability, thereby realizing greater power output over a period of one month. Morphology characterization and thermal degradation process studies reveal that the PM6-b-PY-IT system can overcome stress, probably due to the existence of chemical bonding between the donor and acceptor phase/block, which enables stable phase separation, while excessive phase segregation in the binary all-polymer blend seriously undermines the device performance. This work provides a novel way of achieving high stability OSCs derived from a well-established all-polymer blend, which hopefully will enhance the marketing prospects for this photovoltaic technology.