The charge injection dynamics of dye sensitization from a surface-bound dye (coumarin 343 (C343)) to the conduction band (CB) of the TiO2 is reported here for the first time. Ultrafast fluorescence dynamics demonstrate that the charge injection from the C343 dye to the CB of the TiO2 occurs on a time scale of ca. 200 fs. The charge injection efficiency is attributed to strong electronic coupling between the dye and TiO2 energy levels. The results yield a rate of injection of 5 × 1012 s-1.

Evolution in the charge injection efficiency of evaporated Au contacts on a molecularly doped polymer

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The effects of liquid methanol on the photoluminescence intensity and FTIR spectra of red and blue emitting porous silicon were investigated. Hydrogen passivated red emitting samples exhibit quenching and recovery of photoluminescence intensity and broadening of the Si-Hx stretch bands upon exposure to liquid methanol. Oxygen passivated red emitting samples exhibit no photoluminescence quenching. The sensitivity of the red emitting sample is due to the microstructure of porous silicon at the surface and the ability of methanol to penetrate the pores. The blue photoluminescence of thermally oxidized samples is quenched upon exposure to methanol. This is attributed to the solvent’s ability to change the surface passivation which modifies existing traps and introduces competitive recombination channels for electrons.

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We have investigated the properties of light-emitting porous silicon after ion implantation and successive annealing through continuous-wave photoluminescence (CWPL) and time dependent photoluminescence (TDPL) spectroscopies. Implantation was performed with phosphorus, boron and silicon ions of different doses and energies. Low dose dopant implantation keeps or even increases the CWPL intensity and increases the TDPL decay time. High dose dopant implantation and silicon self-implantation reduce the CWPL intensity and slightly decrease the TDPL decay time.

When CdS and related II‐VI direct bandgap materials form semiconductor clusters in which the absorbance properties are dominated by quantum size effects, the emission properties are particularly sensitive to surface defects, which are associated with the unfilled valence of surface Cd2+ ions. These mid‐bandgap states result in large emission Stokes shifts. This shift can be overcome by binding ligand‐like amines to the surface. By contrast, the more ionic I‐VII materials (e.g., AgBr) show free exciton emission rather than surface defect emission. Since AgBr is an indirect bandgap material, the most obvious effect of size restriction is an increase in the free exciton probability which results from a breakdown in the momentum selection rules at small cluster size.