Tunnel Oxide Deposition Techniques and Their Parametric Influence on Nano-Scaled SiO_x Layer of TOPCon Solar Cell: A Review

Abstract

In addition to the different technologies of silicon solar cells in crystalline form, TOPCon solar cells have an exceptionally great efficiency of 26%, accomplished by the manufacturing scale technique for industrialization, and have inordinate cell values of 732.3 mV open-circuit voltage (Voc) and a fill factor (FF) of 84.3%. The thickness of tunnel oxide, which is less than 2 nm in the TOPCon cell, primarily affects the electrical properties and efficiency of the cell. In this review, various techniques of deposition were utilized for the layer of SiOx tunnel oxide, such as thermal oxidation, ozone oxidation, chemical oxidation, and plasma-enhanced chemical vapor deposition (PECVD). To monitor the morphology of the surface, configuration of annealing, and rate of acceleration, a tunnel junction structure of oxide through a passivation quality of better Voc on a wafer of n-type cell might be accomplished. The passivation condition of experiments exposed to rapid thermal processing (RTP) annealing at temperatures more than 900 °C dropped precipitously. A silicon solar cell with TOPCon technology has a front emitter with boron diffusion, a tunnel-SiOx/n+-poly-Si/ SiNx:H configuration on the back surface, and electrodes on both sides with screen printing technology. The saturation current density (J0) for such a configuration on a refined face remains at 1.4 fA/cm2 and is 3.8 fA/cm2 when textured surfaces of the cell are considered, instead of printing with silver contacts. Following the printing of contacts with Ag, the J0 of the current configuration improves to 50.8 fA/cm2 on textured surface of silicon, which is moderately lesser for the metal contact. Tunnel oxide layers were deposited using many methods such as chemical, ozone, thermal, and PECVD oxidation are often utilized to deposit the thin SiOx layer in TOPCon solar cells. The benefits and downsides of each approach for developing a SiOx thin layer depend on the experiment. Thin SiOx layers may be produced using HNO3:H2SO4 at 60 °C. Environmentally safe ozone oxidation may create thermally stable SiOx layers. Thermal oxidation may build a tunnel oxide layer with low surface recombination velocity (10 cm/s). PECVD oxidation can develop SiOx on several substrates at once, making it cost-effective.

Keywords

• tunnel oxide deposition techniques
• TOPCon solar cell fabrication methods
• TOPCon cell efficiency improvement
• nano-scale SiO_x
• chemical and thermal oxidation
• PECVD