Evaluation of the energetics of electron trap statesat the nanocrystalline titanium dioxide/aqueous solution interfacevia time-resolved photoacoustic spectroscopy

摘要

Time-resolved photoacoustic spectroscopy (TRPAS) has been employed to probe directly the trap state energetics of photogenerated electrons in nanocrystalline colloidal titanium dioxide dispersed in aqueous solutioni. Deconvolution of the photoacoustic signals obtained following bandgap excitation allowed for separation of components associated with conduction band electron trapping, trapped electron-hole recombination, and a slower recombination step. The results indicate that the lifetime of the electron-hole pair is on the order of 25 ns wit about 60% of the trapped electrons recombining on this time scale. The electron trapping sites were determined to lie, on average, 0.8 eV below the conduction band edge.