High-Performance Annealing-Free Polythiophene-Based Organic Solar Cells Enabled by Volatile Solid Additive

Polythiophene (PT)-based organic solar cells (OSCs) present a promising avenue for photovoltaic advancement due to their simple molecular structure and low-cost synthesis. However, their high crystalline characteristics and suboptimal molecular packing hinder efficiency and stability improvement. Herein, we strategically introduced a new in situ volatile solid additive, benzothiophene (BT), engineered for its complete removal during spin-coating, thus eliminating the need for high-temperature annealing. Comparative studies with its analogs with varied numbers of thiophene units, the thermally volatile benzodithiophene (BDT) and nonvolatile benzotrithiophene (BTT), further underscore the advantages of BT additive in refining the intermolecular interactions and optimizing the blend morphology within PTVT-T:BTP-ec9 films. As a result, the OSCs using volatile BT additive achieved an impressive power conversion efficiency (PCE) approaching 18.0% without post-treatment and exceptional thermal stability with a T80 lifespan of over 3365 h. These findings herald the potential of the volatilizable BT additive toward scalable manufacturing of high-efficiency and cost-effective OSCs.