PCE11-based polymer solar cells with high efficiency over 13% achieved by room-temperature processing

Abstract

With the emergence and rapid development of new non-fullerene acceptors (NFAs), bulk-heterojunction polymer solar cells (BHJ-PSCs) have achieved high power conversion efficiencies (PCEs) over 16%. Developing effective methods to fabricate high-performance thick-film PSCs is important to meet the requirements of future roll-to-roll commercial production. PffBT4T-2OD (PCE11) as the most promising temperature-dependent aggregation (TDA) donor with high crystallinity has achieved high performance at high film thickness; however, it needs high processing temperature which is detrimental for practical production of large-area PSCs. We designed NFAs, ZITI-N-CH₃, ZITI-N-C₈H₁₇, and ZITI-N-EH containing different side chains. Because of the excellent miscibility of the TDA-polymer PffBT4T-2OD and ZITI-N-R, devices can be fabricated at room temperature, achieving a medium PCE of 8.78% for ZITI-N-CH₃-based PSCs, a high PCE of 12.13% for ZITI-N-C₈H₁₇-based PSCs and a superior PCE of 13.07% for ZITI-N-EH-based PSCs, which is attributed to the smallest domain size and highest crystallization for the PffBT4T-2OD:ZITI-N-EH blend. The PCE of 13.07% is the highest among those reported for TDA polymer-based PSCs, which can be maintained at 12.35% at a high thickness of 200 nm. This work provides an important guideline to develop high-performance thick-film TDA-polymer-based non-fullerene PSCs under mild processing conditions.