Exciton emission from hybrid organic and plasmonic polytype InP nanowire heterostructures

Abstract

We investigate the emission of excitons in bare, hybrid organic, and metal coated polytype wurtzite/zincblende (WZ/ZB) InP nanowire (NW) heterostructures by intensity- and temperature-dependent time-integrated (TI) and time-resolved (TR) photoluminescence (PL). TI PL measurements at 20 K reveal two strong emission bands at ∼1.48 and ∼1.44 eV that are attributed to non-thermalized weakly and deeply localized indirect WZ/ZB excitons due to randomly distributed short WZ and ZB segments. The PL yield of both bands increases when the NWs are covered with an Alq3 layer which is attributed to surface charge passivation. In metal coated NWs the weakly localized indirect WZ/ZB exciton emission is significantly reduced while the strongly localized indirect WZ/ZB band is less affected. The observed PL quenching is attributed to radiationless Förster energy-transfer from NW excitons to plasmon oscillations in the deposited metal. TR PL investigations support this interpretation revealing enhanced PL lifetimes in Alq3 coated NWs compared to uncovered NWs. The lifetime of weakly trapped indirect excitons is shortest in metal coated NWs due to Förster energy-transfer while the dynamics of strongly localized indirect WZ/ZB excitons is less affected because of the small dipole-moment of these transitions.