Exciton emission from hybrid organic and plasmonic polytype InP nanowire heterostructures

Weinvestigate 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 shortWZand ZB segments. The PL yield of both bands increases when theNWsare covered with an Alq3 layer which is attributed to surface charge passivation. In metal coatedNWsthe weakly localized indirectWZ/ZB exciton emission is significantly reduced while the strongly localized indirectWZ/ZB band is less affected. The observed PL quenching is attributed to radiationless Forster energy-transfer fromNW excitons to plasmon oscillations in the deposited metal. TR PL investigations support this interpretation revealing enhanced PL lifetimes in Alq₃ coatedNWscompared to uncovered NWs. The lifetime of weakly trapped indirect excitons is shortest in metal coatedNWsdue to Forster energytransfer while the dynamics of strongly localized indirect WZ/ZB excitons is less affected because of the small dipole-moment of these transitions.