AVS 59th Annual International Symposium and Exhibition
    Energy Frontiers Focus Topic Wednesday Sessions
       Session EN+TF-WeA

Paper EN+TF-WeA7
Efficient Radiative and Non-Radiative Energy Transfer from Quantum Dots to Silicon Nanomembrane. Evidence of Waveguiding Phenomena

Wednesday, October 31, 2012, 4:00 pm, Room 15

Session: Thin Films for Energy Applications
Presenter: O. Seitz, University of Texas at Dallas
Authors: O. Seitz, University of Texas at Dallas
H.M. Nguyen, University of Texas at Dallas
W. Peng, University of Texas at Dallas
Yu.N. Gartstein, University of Texas at Dallas
Y.J. Chabal, University of Texas at Dallas
A.V. Malko, University of Texas at Dallas
Correspondent: Click to Email
Nanostructured materials attract a considerable attention as potential candidates for practical photovoltaic (PV) devices. The majority of current hybrid PV architectures are based on charge transfer schemes, which frequently suffer from bad interface quality and poor carrier transport, consequently lowering the light conversion efficiency. An alternative is offered by non-contact energy transfer-based hybrid nanostructures, which combine strongly absorbing components, such as inorganic nanocrystal quantum dots (NQDs), and high-mobility semiconductor (SC) layers. It is envisioned that in such hybrid systems, the excitonic energy would be transferred via non-radiative energy transfer (NRET) and radiative (RET) waveguide coupling across the interface with the subsequent separation and transport of charge carriers entirely within the SC-based component. In this talk, we demonstrate the efficient excitonic sensitization of crystalline Si nanomembranes via combined effects of radiative (RET) and non-radiative (NRET) energy transfer from a proximal monolayer of colloidal semiconductor nanocrystals. Ultrathin, 25–300 nm Si films are prepared on top of insulating SiO2 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 non-radiative surface state defects and that the separation between nanocrystals and Si is tightly controlled. Combining atomic force microscopy (AFM), ellipsometry, time-resolved photoluminescence measurements and theoretical modeling, we could identify and quantify the individual contributions from RET and NRET, which all combined exceed 85% efficiency of energy transferred into the Si substrate when the nanocrystals are at about 4 nm from the interface. 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.