Indacenodithiophene-based N-type conjugated polymers provide highly thermally stable ternary organic photovoltaics displaying a performance of 17.5%

In this paper we describe three indacenodithiophene-based conjugated polymers (PITIC-Ph, PITIC-Th, and PITIC-ThF) that we tested as third components for PM6:Y6-based ternary organic photovoltaics (OPVs) to provide high-power conversion efficiencies (PCEs) and long-term thermal stabilities. Among them, the incorporation of PITIC-Ph enhanced the charge dissociation and prohibited the bimolecular (trap-assisted) recombination of the PM6:Y6 blend. Compared with the pre-optimized OPV device, the PCEs of the PITIC-Ph-doped devices improved from 15.0 ± 0.37 to 17.0 ± 0.35% under AM 1.5 G (100 mW cm⁻²) irradiation. More critically, studies of the thermal stability revealed another phenomenon: embedding PITIC-Ph decreased the degree of thermally driven phase segregation of the PM6:Y6 blend film. The respective OPVs exhibited outstanding thermal stability under stress at 150 °C within a glove box, with the PCE of the PITIC-Ph-doped device remaining high (at 16.4%) after annealing for 560 h.