Abstract
The fabrication of bulk heterojunction organic solar cells (OSCs) is primarily based on a phase demixing during solution deposition. This spontaneous process is triggered when, as a result of a decrease in the solvent concentration, interactions between donor and acceptor molecules begin to dominate. Herein, we present that interdiffusion of the same molecules is possible when a bilayers of donors and acceptors are exposed to solvent vapor. Poly(3-hexyl thiophene) (P3HT), and poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole) (PCDTBT) were used as donors and two types of fullerene derivatives were used as acceptors: phenyl-C61-butyric acid methyl ester (PC60BM) and phenyl-C71-butyric acid methyl ester (PC70BM), Secondary ion mass spectrometry depth profiling revealed that the interpenetration of donors and acceptors induced by solvent vapor annealing was dependent on solvent vapor and component compatibility. Exposure to chloroform vapor resulted in a complete intermixing of both components. The mutual mixing increased efficiency of inverted solar cells prepared by solvent vapor annealing of model donor/acceptor bilayers. These results provide a new means for mixing incompatible components for the fabrication of organic solar cells.
Highlights
Organic solar cells (OSCs) have attracted significant attention as new sources of renewable energy due to their low cost, light weight and compatibility for large-format solution deposition production technologies
These results provide a new means for mixing incompatible components for the fabrication of organic solar cells
The basic principles of organic solar cell operation are similar to those for inorganic devices: excitons created by adsorbed light dissociate and free charge carriers move to external electrodes
Summary
Organic solar cells (OSCs) have attracted significant attention as new sources of renewable energy due to their low cost, light weight and compatibility for large-format solution deposition production technologies. Phenomenal improvement has taken place in recent years, and the power conversion efficiency (PCE) of state-of-the-art devices is comparable with commercially available silicon solar cells [1,2,3,4]. This breakthrough could not have been achieved without new materials [5] and has been attributed to a better understanding of the factors that affect OSC fabrication and of the relationship between microstructure and charge generation [4,6,7,8]. The simplest structure fulfilling such requirements is a donor and acceptor bilayer sandwiched between electrodes
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