COLL 330 |
| Multiple exciton generation, by which an absorbed photon generates multiple excitons (electron-hole pairs), was reported recently in a few semiconductor quantum dots. This process allows over 100% quantum efficiency in generating electron-hole pairs, providing a potential way for dramatically improving the solar-to-electric power conversion efficiency in quantum-dot-based solar cells. The next major challenge in utilizing the generated multiple-excitons is to separate the electron-hole pairs before the exciton-exciton annihilation processes, which occurs on the 10s of picosecond time scale. In this paper we report a series of studies of exciton dissociation dynamics at quantum dot–molecular adsorbate interface. Both molecular electron donor and acceptors have been used to investigate the hole and electron transfer processes respectively. We showed that photo-generated exciton in CdS and CdSe can be dissociated on the a few picosecond time scale. We will discuss how to control these rates by changing the relative energetics and electronic coupling strength between the quantum dots and the molecular adsorbates and understand these dependences by the Marcus theory of electron transfer. We will also discuss possible approaches for dissociating multiple excitons in quantum dots. |
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Interfacial Electron Transfer and Solar Energy Conversion: From Molecules to Nanomaterials
2:00 PM-5:40 PM, Tuesday, April 8, 2008 Morial Convention Center -- Rm. 226, Oral
Division of Colloid & Surface Chemistry |