Interplay between TiO₂ Surfaces and Organic Photochromes: A DFT Study of Adsorbed Azobenzenes and Diarylethenes

Abstract

International audienceBecause photochromes act as light-induced molecular switches, there is considerable interest in exporting their molecular functionality in the solid state in order to develop photoresponsive materials. In that context, we have carried out a DFT investigation of a series of photochromic derivatives of trans/cis-azobenzene and open/closed-diarylethene adsorbed onto rutile (110) and anatase (101) slabs. By varying the auxochromes and the photochromic state, we examine the trends in the surface-adsorbate interplay in terms of the electronic structure, adsorption geometries, and Bader charge transfer. Using principal components analysis, we demonstrate how the dipole moment of the isolated photochrome in the direction of the anchoring group is the most important predictor of the electronic structure of the adsorbed system. A key point of this paper is to show how the energy levels of the isolated photochrome and bare slab change as a result of adsorption and how first-principles modeling helps to rationalize and predict these trends

Impact of Ga–V Codoping on Interfacial Electron Transfer in Dye-Sensitized TiO2

“…Another way of CT enhancement is the alteration of the electronic structure of the semiconductor, serving as an electron acceptor. Indeed, the adsorption of molecule on the semiconductor surface modifies its spectral characteristics throughout the hybridization between the native molecular and semiconductor states 7 . It means that changing semiconductor characteristics also can alter electron transfer characteristics of the whole hybrid system.…”

A perspective on using experiment and theory to identify design principles in dye-sensitized solar cells

“…Half-squaraines have been tested in ZnO devices giving η = 0.27% [40] and 0.53% [41] and 3.54% [42] in TiO 2 devices. The synthetic versatility of HfSQs and squaraines has led to the publication of squaraines absorbing across the AM 1.5 solar spectrum, many of which efficiently harvesting light in the near infrared (NIR) [43–46]. This makes these dyes ideal candidates for co-sensitization, i.e.…”

How Adsorption Onto TiO2 Modifies the Properties of Multiswitchable DTE Systems: Theoretical Insights

“…36 In the gas phase systems, photochromes are separated by 10 Å of vacuum in all three periodic directions. To model the hybrid systems, the photochromes are adsorbed perpendicularly onto the anatase surface in a bridging bidentate position, in which the oxygen of the carboxylate anchor are chemisorbed onto the unsaturated titania ions of the surface.…”

“…36 A number of other DFT studies have explored similar hybrid organic-inorganic systems; 37-44 nevertheless, we note that the time-dependent DFT (TD-DFT) computations of optical spectra in a periodic condensed matter context is still far from a routine procedure, though mixed QM:QM' procedures are climbing in popularity. 45,46 The absorption spectra of DTE on gold substrates have also been characterized using cluster models and tight-binding DFT.…”