Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV16)
Publication date: 28th March 2016
Energy transfer has been identified as an important process in ternary organic solar cells. Here, we develop kinetic Monte Carlo (KMC) models to assess the impact of energy transfer in ternary and binary bulk heterojunction systems. We determined the energy transfer parameters for poly(3-hexylthiophene-2,5-diyl), [6,6]-Phenyl-C61-butyric acid methyl ester, 4-bis[4-(N,N-diisobutylamino)-2,6-dihydroxyphenyl] squaraine (DIBSq) and poly(2,5-thiophene-alt-4,9-bis(2-hexyldecyl)-4,9-dihydrodithieno[3,2-c:3′,2′-h][1,5]naphthyridine-5,10-dione). Hetero energy transfer was found to be crucial in the exciton dissociation process of both binary and ternary organic semiconductor systems. Circumstances favouring energy transfer across interfaces allow relaxation of the electronic energy level requirements, meaning that a cascade structure is not required for efficient ternary organic solar cells. It is important that DIBSq is located at the electron donor/acceptor interface otherwise charge carriers will be trapped in the DIBSq domain or excitons in the DIBSq domains will not be able to dissociate efficiently at an interface. KMC modelling shows that only small amounts of DIBSq (<5%) are needed to achieve substantial performance improvements due to long-range energy transfer.