Surface Plasmon Polariton Couplers for Light Trapping in Thin-Film Absorbers and Their Application to Colloidal Quantum Dot Optoelectronics

Optoelectronic devices based on colloidal quantum dots (CQD) are ideal candidates to benefit from plasmonic light trapping, due to fact that they have thin active layers and favorable material constants for absorbing light in the near-field of plasmonic resonances. We demonstrate a simple technique for designing gratings to couple incident light to surface plasmon polariton modes propagating on the metal–semiconductor interface of homojunction PbS CQD photodiodes, providing targeted photocurrent enhancement for solar harnessing or photodetection applications. As a result, an external quantum efficiency of ∼45% is achieved at the exciton peak for a photodiode with an ultrathin PbS CQD absorber of ∼100 nm.