Abstract
We report on the tunnel oxide passivated contact (TOPCon) using a crystalline nanostructured silicon-based layer via an experimental and numerical simulation study. The minority carrier lifetime and implied open-circuit voltage reveals an ameliorated passivation property, which gives the motivation to run a simulation. The passivating contact of an ultra-thin silicon oxide (1.2 nm) capped with a plasma enhanced chemical vapor deposition (PECVD) grown 30 nm thick nanocrystalline silicon oxide (nc-SiOx), provides outstanding passivation properties with low recombination current density (Jo) (~1.1 fA/cm2) at a 950 °C annealing temperature. The existence of a thin silicon oxide layer (SiO2) at the rear surface with superior quality (low pinhole density, Dph < 1 × 10−8 and low interface trap density, Dit ≈ 1 × 108 cm−2 eV−1), reduces the recombination of the carriers. The start of a small number of transports by pinholes improves the fill factor (FF) up to 83%, reduces the series resistance (Rs) up to 0.5 Ω cm2, and also improves the power conversion efficiency (PEC) by up to 27.4%. The TOPCon with a modified nc-SiOx exhibits a dominant open circuit voltage (Voc) of 761 mV with a supreme FF of 83%. Our simulation provides an excellent match with the experimental results and supports excellent passivation properties. Overall, our study proposed an ameliorated knowledge about tunnel oxide, doping in the nc-SiOx layer, and additionally about the surface recombination velocity (SRV) impact on TOPCon solar cells.
Highlights
In recent times, silicon solar cells using a tunnel oxide passivated contact (TOPCon) cell structure [1,2,3,4,5,6,7,8,9], or alternatively, a poly-silicon wafer (Si) on passivating interfacial oxides (POLO) structure [10], have established an outstanding potential as well as having collected substantial consideration
The refractive index (n) of the nanocrystalline silicon oxide (nc-SiOx) films was estimated from spectroscopic ellipsometric measurements
Analysis of Passivation Properties Note that the implied open-circuit voltage, derived from implicit current–voltage characteristic curves of the quasi-steady-state photoconductance (QSSPC), is an essential parameter to evaluate the overall performance of a silicon solar cell, as it reflects the quality of surface passivation and the
Summary
Silicon solar cells using a tunnel oxide passivated contact (TOPCon) cell structure [1,2,3,4,5,6,7,8,9], or alternatively, a poly-Si on passivating interfacial oxides (POLO) structure [10], have established an outstanding potential as well as having collected substantial consideration. Our research on the TOPCon solar cells aimed to (a) demonstrate a mechanism for enhancing cell performance in a TOPCon structure; (b) achieve an efficiency exceeding 27% utilizing the TOPCon cell configuration; (c) conduct extensive research on high-quality passivating contacts, such as stacks of ncSiOx(n)/SiOx contacts, which are at the cutting edge in the latest photovoltaic (PV) research; (d) establish a systematic experimental and simulation procedure for the TOPCon cell; and (e) propose a method of increasing the performance of TOPCon cells This unconventional structure contains a thermally grown thin silicon oxide layer (SiO2) on both sides of the c-Si wafer, with a surface covered by a phosphorus-doped nanocrystalline silicon oxide (nc-SiOx) on both sides. Our findings furnish an additional understanding of the challenges and limitations referring to the primary factors; they will provide a direction for developing high-efficiency TOPCon solar cells
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