Charge transfer at organic-inorganic interfaces

TL;DR

This study investigates electron transfer dynamics at organic-inorganic interfaces using femtosecond photoluminescence measurements on dye layers with various parameters, revealing key factors influencing transfer times.

Contribution

It provides a detailed analysis of how structural and energetic parameters affect electron transfer times at organic-inorganic interfaces, offering insights for optimizing such systems.

Findings

Transfer times correlate with the number of anchoring groups.

Distance between dye and interface significantly affects transfer speed.

Layer thickness and energy level alignment also influence electron transfer.

Abstract

We studied the electron transfer from excitons in adsorbed indoline dye layers across the organic-inorganic interface. The hybrids consist of indoline derivatives on the one hand and different inorganic substrates (TiO$_2$, ZnO, SiO$_2$(0001), fused silica) on the other. We reveal the electron transfer times from excitons in dye layers to the organic-inorganic interface by analyzing the photoluminescence transients of the dye layers after femtosecond excitation and applying kinetic model calculations. A correlation between the transfer times and four parameters have been found:(i) the number of anchoring groups, (ii) the distance between the dye and the organic-inorganic interface, which was varied by the alkyl-chain lengths between the carboxylate anchoring group and the dye, (iii) the thickness of the adsorbed dye layer, and (iv) the level alignment between the excited dye ($\pi$*-level) and the conduction band minimum of the inorganic semiconductor.