Exciton emission from hybrid organic and plasmonic polytype InP nanowire heterostructures

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 Alq 3 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 Alq 3 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.