A Family of Small Molecular Materials Enabling Consistently Lower Recombination Losses in Organic Photovoltaic Devices. Issue 10 (21st July 2020) - Chandran, Hrisheekesh Thachoth
Abstract : Hybridization between the charge transfer (CT) state of a donor–acceptor pair and lowest exciton state of the donor or the acceptor is reported to be effective for reducing recombination loss in organic photovoltaic (OPV) devices. Although this approach shows great success in maximizing open circuit voltage ( V oc ), it is typically accompanied by low device performance. Here, "complete boron sub‐(na)phthalocyanine devices" with strong hybridization resulting in lower recombination loss (≈0.47 eV) while not penalizing charge separation dynamics (internal quantum efficiency (IQE) > 80% and fill factor (FF) > 70%) are reported. Interestingly, when boron sub‐(na)phthalocyanine is paired with any other active material used in this study ("partial boron sub‐(na)phthalocyanine device"), recombination losses are still consistently maintained at lower levels (<0.53 eV). These observations denote the capability of boron sub‐(na)phthalocyanine to result in lower recombination loss devices while pairing with other materials. Special intrinsic characteristics of these materials (high dielectric constant, sharp absorption edge, unusually high absorption coefficient) and hybridization collectively result in reduced recombination loss and efficient charge generation in these systems. Abstract : Boron sub‐(na)phthalocyanine chloride–based organic photovoltaic devices exhibit extremely low recombination loss (≈0.50 eV) while not penalizing charge separation (internal quantum efficiency > 80%). Unique intrinsic properties of these materials and hybridization collectively result in low recombination loss and effective charge separation at the same time.