Sputtered Ultrathin TiO2 as Electron Transport Layer in Silicon Heterojunction Solar Cell Technology

Abstract

first_pagesettingsOrder Article Reprints Open AccessEditor’s ChoiceArticle Sputtered Ultrathin TiO2 as Electron Transport Layer in Silicon Heterojunction Solar Cell Technology by Susana Fernández *ORCID,Ignacio Torres *ORCID andJosé Javier Gandía Departamento de Energía, CIEMAT, Avenida Complutense 40, 28040 Madrid, Spain * Authors to whom correspondence should be addressed. Nanomaterials 2022, 12(14), 2441; https://doi.org/10.3390/nano12142441 Submission received: 31 May 2022 / Revised: 23 June 2022 / Accepted: 14 July 2022 / Published: 16 July 2022 (This article belongs to the Special Issue Solar Cells Based on Titanium Dioxide Nanomaterials) Downloadkeyboard_arrow_down Browse Figures Versions Notes Abstract This work presents the implementation of ultrathin TiO2 films, deposited at room temperature by radio-frequency magnetron sputtering, as electron-selective contacts in silicon heterojunction solar cells. The effect of the working pressure on the properties of the TiO2 layers and its subsequent impact on the main parameters of the device are studied. The material characterization revealed an amorphous structure regardless of the working pressure; a rougher surface; and a blue shift in bandgap in the TiO2 layer deposited at the highest-pressure value of 0.89 Pa. When incorporated as part of the passivated full-area electron contact in silicon heterojunction solar cell, the chemical passivation provided by the intrinsic a-Si:H rapidly deteriorates upon the sputtering of the ultra-thin TiO2 films, although a short anneal is shown to restore much of the passivation lost. The deposition pressure and film thicknesses proved to be critical for the efficiency of the devices. The film thicknesses below 2 nm are necessary to reach open-circuit values above 660 mV, regardless of the deposition pressure. More so, the fill-factor showed a strong dependence on deposition pressure, with the best values obtained for the highest deposition pressure, which we correlated to the porosity of the films. Overall, these results show the potential to fabricate silicon solar cells with a simple implementation of electron-selective TiO2 contact deposited by magnetron sputtering. These results show the potential to fabricate silicon solar cells with a simple implementation of electron-selective TiO2 contact.