22.8% efficient ion implanted PERC solar cell with a roadmap to achieve 23.5% efficiency: A process and device simulation study

Abstract

Among all available photovoltaic (PV) technology options, c-Si based passivated emitter rear cell (PERC) has already proved its mettle by delivering more than 22% conversion efficiency at the industrial level. However, designing of PERC solar cell device remains a challenge owing to recombination and absorption losses, which eventually restrict the performance of the device toward achieving an Auger efficiency limit of 29.4%. The primary contributor to these losses is emitter recombination losses that limits the performance of PERC devices. The n+-emitter region in the proposed PERC devices is formed using ion implantation followed by a diffusion process. The impact of process variables such as dose (cm−2), energy (keV), diffusion time (s), and diffusion temperature (oC) on the PERC device performance is not much explored. Therefore, in an attempt to fulfill this research gap, the emitter region performance in terms of ion implantation of phosphorus, influence of local back surface field (BSF) doping concentration (1017 to 1019 cm−3), and back surface recombination velocity (SRV 101–107 cm/s) on PERC device performance followed by the loss analysis is examined in this work. An upright pyramid textured structure with constant height (5 μm) and industrial standard stacked dielectric anti-reflective coating layers, SiNX/SiO2 and Al2O3/SiNX at front and back side respectively is realized using different process statements such as deposit, etch, implantation, and diffusion with the help of a Silvaco TCAD software. Investigations reveal that the PERC device can deliver an efficiency of 22.8% with 150 μm boron-doped crystalline silicon (c-Si) wafer at an optimum phosphorous dose (5 × 1015 cm−2), BSF doping (1019 cm−3), and SRVn (107 cm/s). Short-circuit current density (JSC) of 40.8 mA/cm2, open-circuit voltage (VOC) of 0.686 V, and fill factor (FF) of 81.54% are obtained for the structure under consideration. A roadmap to achieve 23.5% conversion efficiency has also been reported by assuming a carrier selective contact at the backside with a surface recombination velocity of 10 cm/s.