Abstract
In the fabrication of crystalline silicon solar cells, the contact properties between the front metal electrode and silicon are one of the most important parameters for achieving high-efficiency, as it is an integral element in the formation of solar cell electrodes. This entails an increase in the surface recombination velocity and a drop in the open-circuit voltage of the solar cell; hence, controlling the recombination velocity at the metal-silicon interface becomes a critical factor in the process. In this study, the distribution of Ag crystallites formed on the silicon-metal interface, the surface recombination velocity in the silicon-metal interface and the resulting changes in the performance of the Passivated Emitter and Rear Contact (PERC) solar cells were analyzed by controlling the firing temperature. The Ag crystallite distribution gradually increased corresponding to a firing temperature increase from 850 ∘C to 950 ∘C. The surface recombination velocity at the silicon-metal interface increased from 353 to 599 cm/s and the open-circuit voltage of the PERC solar cell decreased from 659.7 to 647 mV. Technology Computer-Aided Design (TCAD) simulation was used for detailed analysis on the effect of the surface recombination velocity at the silicon-metal interface on the PERC solar cell performance. Simulations showed that the increase in the distribution of Ag crystallites and surface recombination velocity at the silicon-metal interface played an important role in the decrease of open-circuit voltage of the PERC solar cell at temperatures of 850–900 ∘C, whereas the damage caused by the emitter over fire was determined as the main cause of the voltage drop at 950 ∘C. These results are expected to serve as a steppingstone for further research on improvement in the silicon-metal interface properties of silicon-based solar cells and investigation on high-efficiency solar cells.
Highlights
Among the recent trends of research in the photovoltaic industry, a Passivated Emitter and Rear Contact (PERC) structure that minimizes surface recombination through passivation layers on the front and rear sides of a solar cell has gained considerable interest
As the simulation result showed a similar pattern to the surface recombination velocity changes of Ag crystallites obtained by experimental measurements, it is considered that the recombination properties of Ag crystallites have induced changes in the PERC solar cell performance
This study investigated the distribution of Ag crystallites, saturation current density, surface recombination velocity, and changes in the performance of PERC solar cells at the silicon–metal interface for different firing temperatures
Summary
Among the recent trends of research in the photovoltaic industry, a Passivated Emitter and Rear Contact (PERC) structure that minimizes surface recombination through passivation layers on the front and rear sides of a solar cell has gained considerable interest. The front-side recombination of PERC solar cells directly impact the open-circuit voltage of solar cells and is one of the key factors affecting the efficiency loss of solar cells. This frontside recombination is represented as leakage current in reverse direction on the equivalent circuit, and the leakage current is defined as saturation current density. The high value of J0.metal reduces the open-circuit voltage of solar cells; reducing J0.metal is one of the pivotal factors in the manufacturing of high-efficiency solar cells [4,5,6,7,8,9]. While most research on solar cell efficiency enhancement has been conducted to date on the passivation properties of solar cells, as research with this approach is reaching its limit, there is a need for research with a strategic approach that focuses on reducing the recombination by electrodes
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