Facile grown native oxide based passivation of crystalline silicon: A novel approach for low-temperature synthesis of silicon photovoltaics

Passivation of the crystalline silicon surface is central to the attainment of high-efficiency silicon solar cells and even more so as the silicon absorber is thinned. Moreover, the current predominantly high temperature processing of thin silicon wafers gives rise to defect migration-creation and thermal stresses in a typical multi-layered photovoltaic (PV) device. The development of a simple and effective low temperature passivation scheme would aid immensely in the synthesis of next generation low-cost high-efficiency thin silicon solar cells.;This research proposes, investigates and demonstrates the efficacy of a novel low-temperature passivation scheme for crystalline silicon surface which consists of a facile grown native oxide (SiOx) layer and a silicon nitride (SiNx) over layer. A systematic experimental study of the interfacial passivation quality reveals that high quality surface passivation is obtained at a saturation native oxide thickness of ~10A. The passivation quality is uniform over a large silicon surface with a surface recombination velocity (SRV) of 8 cm/s. Recombination modelling of the interface shows that the interfacial defect density diminishes with increasing native oxide thickness while the trapped charge density is essentially unchanged.;In light of the new passivation scheme, this research investigates theoretically and experimentally a legacy photovoltaic cell concept, the Back Amorphous-Crystalline silicon Heterojunction (BACH) PV device, and proposes a novel PV cell concept -- the Lateral Inherently Thin (LIT) amorphous-crystalline silicon heterojunction PV device.;Benchmarked theoretical studies of the devices, using Sentaurus -- a device modelling code, indicate a maximum BACH cell and LIT cell efficiency of 24.4% and 23.9%, respectively, for a 100mum thick textured cSi substrate with attainable (10 cm/sec) passivation quality.;BACH and LIT PV devices, integrating the new facile grown SiOx passivation scheme, were fabricated using n-type double-side polished 280mum thick (100) FZ cSi wafers. An optimal untextured cell efficiency of 16.7% and 11.6% are obtained for a 1 cm2 BACH and LIT devices, respectively, under AM1.5 solar irradiation.;Development of the high quality facile grown oxide based passivation scheme, a paradigm shift relative to conventional thermal oxide passivation, paves the path for low-temperature synthesis of oxide-based high quality semiconductor devices on thin silicon -- including high-efficiency silicon photovoltaics.