Electronic structure of dye-sensitized TiO2clusters from many-body perturbation theory

Abstract

The development of new types of solar cells is driven by the need for clean and sustainable energy. In this respect dye sensitized solar cells (DSC) are considered as a promising route for departing from the traditional solid state cells. The physical insight provided by computational modeling may help develop improved DSCs. To this end it is important to obtain an accurate description of the electronic structure, including the fundamental gaps and level alignment at the dye-TiO 2 interface. This requires a treatment beyond ground-state density functional theory (DFT). We present a many-body perturbation theory study, within the G 0 W 0 approximation, of two of the crystalline phases of dye-sensitized TiO 2 clusters, reported by Benedict and Coppens [J Am Chem Soc 132 (9), 2938 (2010)]. We obtain geometries in good agreement with experiment by using DFT with the Tkatchenko-Scheffler van der Waals correction. We demonstrate that even when DFT gives a good description of the valence spectrum and a qualitatively correct picture of the electronic structure of the dye-TiO 2 interface, G 0 W 0 calculations yield more valuable quantitative information regarding the fundamental gaps and level alignment. In addition, we systematically investigate the issues pertaining to G 0 W 0 calculations, namely: (i) convergence with respect to the number of basis functions, (ii) dependence on the mean field starting point, and (iii) the validity of the assumption that the DFT wave-function is a good approximation to the quasi-particle wave-function. We show how these issues are manifested for dye molecules and for dye-sensitized TiO 2 clusters.

Benchmark ofGWmethods for azabenzenes

“…They embody the basic physics of such systems including the strong correlation effects in aromatic π-systems 84,89,92 and the self-interaction effects introduced by the nitrogen lone pairs. 51,59 Another advantage of these systems is that they are well-characterized experimentally [93][94][95][96][97][98][99][100][101][102][103][104][105][106][107][108] and well-studied theoretically by high-level wavefunction and Green's function methods. 93,104,[109][110][111][112][113][114][115][116][117][118][119][120][121][122] We calculate the electronic structure of benzene, pyridine, and the diazines using: (i) semi-local and hybrid DFT (ii) G 0 W 0 , (iii) ev-scGW, (iv) scGW 0 , (v) scGW, and (vi) G 0 W 0 combined with the second-order exchange self-energy (2OX), as an attempt to go beyond the GW approximation.…”

“…43,51,[59][60][61]66 It has been suggested that self-interaction errors (SIE), the spurious interaction of an electron with itself, 67 at the DFT level lead to a strong starting point dependence of G 0 W 0 calculations and to the inadequacy of a semi-local starting point. 32,59,61 Indeed, the propagation of SIE from DFT to GW has been demonstrated explicitly for oneelectron systems. [68][69][70] In such cases, the inclusion of a fraction of exact exchange (EXX) in hybrid functionals mitigates SIE and often provides a better starting point for G 0 W 0 calculations.…”

“…1, [30][31][32][33][34][35][36][37][38][39][40][41][42] ) and has had some notable success in the description of the electronic structure of various organic 10,13,[43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60] and metal-organic molecules, 59, 61 as well as organic-inorganic interfaces. [8][9][10][11][12][13][14][15][16] However, the non-self-consistency gives rise to a dependence of the G 0 W 0 results on the DFT starting point.…”

Assessment of the performance of tuned range-separated hybrid density functionals in predicting accurate quasiparticle spectra

“…It must be borne in mind that the results of G 0 W 0 calculations can depend significantly on the chosen DFT starting point. [18][19][20][21][22] Consequently, a DFT-based approach that could yield accurate QP energies for both occupied and unoccupied states is highly desirable, not only to extend the range of systems for which reliable QP energies can be obtained, but also as a suitable starting point for G 0 W 0 calculations.…”

Fotocolheita em interface híbrida de molécula orgânica e óxido de titânio

“…Alguns trabalhos da literatura [30,31,32] que tentaram abordar este problema optaram por simular o material semicondutor através de um aglomerado de pouquíssimos átomos, longe de se equiparar a uma nanopartícula. O estudo de sistemas da ordem de grandeza dos reais, porém, é impraticável computacionalmente, e por isso adota-mos o uso da periodicidade (filmes 2D) para a descrição do nosso sistema.…”