抄録
A quantum confinement in a nanoscale material opens various kinds of photochemical dynamics which have never been found in bulk materials nor in small molecules. Multiple exciton generation provides a potential route to increase a photovoltaic efficiency by creating multiple charge carriers from a single photon absorption, while multiple exciton recombination, in which a multiple exciton annihilates to a single exciton of high energy, reduces a solar cell efficiency by accelerating energy losses to heat. Electron transfer (ET) from a semiconductor nanomaterial to an adsorbate accompanying hole excitation due to electron-hole energy exchange eliminates the unfavorable Marcus inverted regime and thus cannot be described by Marcus ET theory. We have developed real-time ab initio molecular dynamics simulations and analytic theories to describe such novel photoexcited dynamics taking place in semiconductor quantum dots of different sizes and components with and without ligands, in its complex with a chromophore, and in a carbon nanotube. Our methods have not only rationalized the recent experimental observations but also revealed complex interplays of electron-hole and electron-phonon channels of energy exchange, suggesting a variety of scenarios after a photoexcitation of electrons, holes and excitons.
