Properties of Thermally Evaporated Titanium Dioxide as an Electron-Selective Contact for Silicon Solar Cells

Abstract

Recently, titanium oxide has been widely investigated as a carrier-selective contact material for silicon solar cells. Herein, titanium oxide films were fabricated via simple deposition methods involving thermal evaporation and oxidation. This study focuses on characterizing an electron-selective passivated contact layer with this oxidized method. Subsequently, the SiO2/TiO2 stack was examined using high-resolution transmission electron microscopy. The phase and chemical composition of the titanium oxide films were analyzed using X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The passivation quality of each layer was confirmed by measuring the carrier lifetime using quasi-steady-state photoconductance, providing an implied open circuit voltage of 644 mV. UV–vis spectroscopy and UV photoelectron spectroscopy analyses demonstrated the band alignment and carrier selectivity of the TiO2 layers. Band offsets of ~0.33 and ~2.6 eV relative to the conduction and valence bands, respectively, were confirmed for titanium oxide and the silicon interface.

Recent Progress in Interconnection Layer for Hybrid Photovoltaic Tandems

“…Alternative high‐conductive contact based on low‐damage deposition processes such as chemical vapor deposition (CVD), atomic layer deposition (ALD), or remote‐plasma deposition needs to be developed. [ 94,95 ]…”

Boron‐doped polysilicon using spin‐on doping for high‐efficiency both‐side passivating contact silicon solar cells

“…In this poly‐Si passivating contact, the tunnel oxide prevents direct contact between the metal and bulk silicon, thereby reducing recombination losses. In addition, the tunnel oxide functions as a passivation layer that allows majority carriers to flow by tunneling and avoids the flow of minority carriers into the defective poly‐Si layer, leading to high carrier selectivity and an increase in cell efficiency 3–7 . The cells fabricated with rear n + poly‐Si contact and front BB ‐diffused emitter showed a record efficiency of 26.0% 8 .…”

“…In addition, the tunnel oxide functions as a passivation layer that allows majority carriers to flow by tunneling and avoids the flow of minority carriers into the defective poly-Si layer, leading to high carrier selectivity and an increase in cell efficiency. [3][4][5][6][7] The cells fabricated with rear n + poly-Si contact and front BBR 3 -diffused emitter showed a record efficiency of 26.0%. 8 The cell with p + and n + poly-Si passivating contacts for hole and electron contacts, respectively, can further reduce recombination originating from both types of contacts and improve cell efficiency.…”

Monolithic Perovskite-Carrier Selective Contact Silicon Tandem Solar Cells Using Molybdenum Oxide as a Hole Selective Layer

“…Recently, a high value of carrier lifetime can be obtained by improving the silicon interface passivation characteristics [16]. Hence, studies on carrier selective contacts using carbon-based materials [17,18] and metal oxides such as TiO 2 , ZnO, and MoO x , which can be easily deposited, have attracted renewed attention [19][20][21]. Unlike conventional p-n junction cells with built-in electric fields formed by a doping process to separate photogenerated carriers, the carrier selective contact structure separates the carriers by band bending generated between the material being contacted and the silicon.…”