This paper presents experimental evidence that silicon solar cells can achieve >750 mV open circuit voltage at 1 Sun illumination providing very good surface passivation is present. 753 mV local open circuit voltage was measured on a 50 μm thick non-metalized silicon heterojunction solar cell. The paper also considers a recombination model at open circuit based on the recent Auger and radiative recombination parameterization and the measured surface saturation current density. The loss mechanisms at open circuit and several practical pathways to achieve >760 mV open circuit voltage in silicon heterojunction solar cells are discussed.
The mathematical dependence of bandgap-voltage offset on Auger and radiative recombination is derived. To study the recombination near the intrinsic limit, we manufacture thin silicon heterojunction test structures designed to minimize surface recombination, and to measure voltages and effective lifetimes near the Auger and radiative limit. Open-circuit voltages over 760 mV were measured on 50-μm-thick structures, leading to bandgap-voltage offsets at open-circuit down to 0.35 V. The Auger and radiative recombination represents over 90% of the recombination at open-circuit. This dominance also holds at the maximum power point, giving pseudo-fill factors of 86%. We demonstrate the potential of thin silicon devices to reach high voltages, and bandgap-voltage offsets in line with the best reported for direct bandgap materials such as gallium indium phosphide and gallium arsenide.
High quality surface passivation (Seff < 5 cm/s) was achieved on polished float zone and textured p- and n-type solar grade Czochralski silicon substrates by externally injecting and storing positive or negative charges (>±8 × 1012 cm−2) into a dual layer stack of Plasma Enhanced Chemical Vapor Deposition (PECVD) Silicon Nitride (SiNx)/PECVD Silicon Oxide (SiO2) films using a corona charging tool. We demonstrate long term stability and uniform charge distribution in the SiNx film by manipulating the charge on K center defects while negating the requirement of a high temperature thermal oxide step.
A method of reducing optical losses in the transparent conductive oxides (TCO) used in silicon heterojunction solar cells without compromising with series resistance is described. In the method the thickness of a TCO is reduced two-three times and a hydrogenated dielectric is deposited on top to form a double layer antireflection coating. The conductivity of a thin TCO is increased due to the effect of hydrogen treatment supplied from the capping dielectric during the post deposition annealing. The optimized cells with ITO/SiO x :H stacks achieved more than 41 mA/cm 2 generation current on 120-micron-thick wafers while having approximately 100 Ohm/square sheet resistance. The paper also considers integration of ITO/SiO x :H stacks with Cu plating and using ITO/SiN x /SiO x triple layer antireflection coatings.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.