Stoichiometry Gradient, Cation Interdiffusion, and Band Alignment between a Nanosized TiO2 Blocking Layer and a Transparent Conductive Oxide in Dye-Sensitized Solar Cell Front Contacts

Year: 2015

Authors: Salvinelli G., Drera G., Baratto C., Braga A., Sangaletti L.

Autors Affiliation: Interdisciplinary Laboratories for Advanced Materials Physics (I-LAMP) and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, I-25121 Brescia, Italy;
CNR INO Sensor Lab, Via Branze 45, 25133 Brescia, Italy;
University of Brescia, Dept. of Information Engineering, Via Valotti 9, 25133 Brescia, Italy

Abstract: An angle-resolved photoemission spectroscopy study allowed us to identify cation interdiffusion and stoichiometry gradients at the interface between a nanosized TiO2 blocking layer and a transparent conductive Cd-Sn oxide substrate. A stoichiometry gradient for the Sn cations is already found in the bare Cd-Sn oxide layer. When TiO2 ultrathin layers are deposited by RF sputtering on the Cd-Sn oxide layer, Ti is found to partially replace Sn, resulting in a Cd-Sn-Ti mixed oxide layer with a thickness ranging from 0.85 to 3.3 nm. The band gap profile across the junction has been reconstructed for three TiO2 layers, resulting in a valence band offset decrease (and a conduction band offset increase) with the blocking layer thickness. The results are related to the cell efficiencies in terms of charge injection and recombination processes.


Volume: 7 (1)      Pages from: 765  to: 773

KeyWords: DSSC; blocking layer;
DOI: 10.1021/am5072018

Citations: 8
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