Low-temperature Ta-doped TiOx electron-selective contacts for high-performance silicon solar cells

Abstract

Carrier-selective contacts have been widely used to reduce the recombination losses of the minority carriers and boost the transport of the majority carriers at the contact regions for high-performance crystalline silicon solar cells. In this paper, the electron-selective Ta-doped TiOx (TTO) thin films with wide bandgap were prepared by means of low-temperature atomic layer deposition (ALD) technique. The systematic examinations were conducted on the interfacial structures, elemental analysis, passivation, and electrical performance of the TTO films. The results demonstrated that ALD TTO thin films possess better surface passivation (τeff = 355.31 μs, 130 °C annealing), and excellent electrical performance (ρc = 0.7 mΩ cm2, 200 °C annealing) on c-Si, in comparison to pure TiOx and TaOx films. Benefiting from these advantages, the optimized TTO based electron-selective contact solar cell achieved a high power conversion efficiency (PCE) of 21.58 %, reaching the cutting-edge level of the wide bandgap oxide based electron-selective contact solar cells. The low-temperature, low-energy-consumption and simple ALD TTO electron-selective contacts present a promising approach for Si-based high-efficiency solar cells.