Efficient hybrid colloidal quantum dot/organic solar cells mediated by near-infrared sensitizing small molecules

Solution-processed semiconductors are promising materials to realize optoelectronic devices that combine high performance with inexpensive manufacturing. In particular, the exploitation of colloidal quantum dots (CQDs) capable of harvesting infrared photons, in conjunction with visible-absorbing organic chromophores, has been demonstrated as an interesting route. Unfortunately, CQD/organic hybrid photovoltaics have been limited to power conversion efficiencies (PCEs) below 10% due to chemical mismatch and difficulties in facilitating charge collection. Here we devise a hybrid architecture that overcomes these limitations by introducing small molecules into the CQD/organic stacked structure. The small molecule complements CQD absorption and creates an exciton cascade with the host polymer, thus enabling efficient energy transfer and also promoting exciton dissociation at heterointerfaces. The resulting hybrid solar cells exhibit PCEs of 13.1% and retain over 80% of their initial PCE after 150 h of continuous operation unencapsulated, outperforming present air-processed solution-cast CQD/organic photovoltaics. Colloidal quantum dots and organics have complementary properties apt for photovoltaics, yet their combination has led to poor charge collection. Here, Baek et al. introduce small molecules that act as a bridge between quantum dots and polymers, thus improving device efficiency and stability.