Organic Dye Graphene Hybrid Structures with Spectral Color Selectivity

This study characterizes a hybrid structure formed between graphene and organic dye molecules for use in photodetectors with spectral color selectivity. Rhodamine-based organic dye molecules with red, green, or blue light absorption profiles are deposited onto a graphene surface by dip-coating. UV–vis absorption spectroscopy, charge transport measurements, and density functional theory based calculations reveal that the photoresponses of the dye graphene hybrid films are governed by the light absorption of the dye molecules and also by the photo-excited-charge-transfer-induced photocurrent gain. The hybrid films respond only to photons with an energy exceeding the band gap of the immobilized dye. Dye-Graphene charge transfer is affected by the distance and direction of the dipole moment between the two layers. The resulting hybrid films exhibit spectral color selectivities with responsivities of ≈10³ A W⁻¹ and specific detectivities of ≈10¹⁰ Jones. This study demonstrates the successful operation of photodetectors with a full-color optical bandwidth using hybrid graphene structures coated with a mixture of dyes. The strategy of building a simple hybrid photodetector can further offer many opportunities to be also tuned for other optical functionalities using a variety of commercially available dye molecules.