title: Efficient radiative and nonradiative energy transfer from proximal CdSe/ZnS nanocrystals into silicon nanomembranes.
abstract: We demonstrate efficient excitonic sensitization of crystalline Si nanomembranes via combined effects of radiative (RET) and nonradiative (NRET) energy transfer from a proximal monolayer of colloidal semiconductor nanocrystals. Ultrathin, 25-300 nm Si films are prepared on top of insulating SiO(2) substrates and grafted with a monolayer of CdSe/ZnS nanocrystals via carboxy-alkyl chain linkers. The wet chemical preparation ensures that Si surfaces are fully passivated with a negligible number of nonradiative surface state defects and that the separation between nanocrystals and Si is tightly controlled. Time-resolved photoluminescence measurements combined with theoretical modeling allow us to quantify individual contributions from RET and NRET. Overall efficiency of ET into Si is estimated to exceed 85% for a short distance of about 4 nm from nanocrystals to the Si surface. Effective and longer-range radiative coupling of nanocrystal's emission to waveguiding modes of Si films is clearly revealed. This demonstration supports the feasibility of an advanced thin-film hybrid solar cell concept that relies on energy transfer between strong light absorbers and adjacent high-mobility Si layers.
authors.affiliation: Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080, USA.
authors.forename: Hue M
authors.initials: HM
authors.lastname: Nguyen
authors.forename: Oliver
authors.initials: O
authors.lastname: Seitz
authors.forename: Weina
authors.initials: W
authors.lastname: Peng
authors.forename: Yuri N
authors.initials: YN
authors.lastname: Gartstein
authors.forename: Yves J
authors.initials: YJ
authors.lastname: Chabal
authors.forename: Anton V
authors.initials: AV
authors.lastname: Malko
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry*; D004735:Energy Transfer; D008422:Materials Testing; D008567:Membranes, Artificial; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D018036:Selenium Compounds / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry*; D017967:Zinc Compounds / Q000737:chemistry*
chemical_list: D019187:Cadmium Compounds; D008567:Membranes, Artificial; D018036:Selenium Compounds; D017967:Zinc Compounds; C058667:cadmium selenide; C044696:zinc selenide; D012825:Silicon