Probing Charge Generation in 3D Photonic Poly(3-hexylthiophene)/Titanium Dioxide Nanocomposites for Bulk Heterojunction Solar Cells

Organic photovoltaics (OPVs) are attractive for their inexpensiveness, large-scale fabrication methods, flexibility and semi-transparency. OPVs have lower efficiencies than conventional inorganic semiconductor-based solar cells, and hence methods to enhance light-harvesting properties are sought-after. Photonic crystals are unique nanomaterials that present the ability to enhance light-harvesting properties through electromagnetic field localization and slow photon effect. In this work, three-dimensional photonic crystals were successfully integrated into the active layers of bulk-heterojunction solar cells by fabricating a series of titanium dioxide inverse opals coated with poly(3-hexylthiophene). The optical, morphological, and charge generation properties of the nanocomposites were investigated. Transient photoinduced absorption spectroscopy showed enhanced charge generation due to a potential photonic enhancement and the increased interfacial area of the porous structure. This research serves as a proof of concept, where the photonic properties of inverse opals and their high surface area may be exploited with different materials in other solar cell systems.