16 Décembre – Thesis defense - Robin Szymanski
10 h Amphi 3 - Bordeaux INP, ENSCBP (Pessac)
Towards the industrialization of organic ternary solar cells.
Organic photovoltaics (OPV) is a promising solar energy technology excluding the usage of rare elements and with low production costs. These multilayer OPV modules can be flexible, semi-transparent and with various colors enabling innovative usage in the urban landscape and on our everyday technological items. At lab scale, over the years, the power conversion efficiency of OPV cells grew up dramatically, especially thanks to the development of novel active layers, blends of two organic semiconductors, one electron donor and one electron acceptor (binary system). Recently, it has been shown that adding a third material in the active layer, forming a ternary blend, increases the performances. This strategy is of interest for the OPV industry by maintaining the low production costs of the modules. Therefore, this work aims to understand the role of this third component and to develop innovative active layers while respecting the industrial requirements for large-scale production. First, we focused on binary blends with PTQ10 and DT-PPDT2T-TT as polymeric donors. Promising efficiencies were achieved on these binary systems as a base for our ternary studies. We tried to increase the short circuit current by adding a third organic semiconductor with complementary light absorption. This approach was not successful because the fill factor dropped drastically. Thus, we focused on improving this parameter by adding the well-known fullerene acceptor PC61BM. This strategy enabled to increase the efficiency up to 10.3% in semi-industrial conditions with a non-toxic solvent and up to 14.7% in halogenated solvent. Morphological changes were responsible of charge transport improvement, which has proven to be one of the key factor in ternary blends. In addition, the open circuit voltage has been shown proportional to the weight ratio between both acceptors when they form an alloy. Based on these studies, we developed a predictive approach to assess the compatibility between the materials. Finally, ternary PTQ10:4TIC-4F:PC61BM devices turned out to be the most promising in terms of pre-industrialization and photostability.