A simple optical model to facilitate assessment of photovoltaic concentrator system components

Several novel thin film coated cover glasses are designed for use in multi-junction concentrator modules. These robust cover glasses offer performance benefits over standard encapsulants, including promotion of light into the current-limiting sub-cell, improvement of the current balance between sub-cells, and additional passive temperature reduction. In order to optimise the coatings, a mathematical model of a simple concentrator system was devised. The model shows that the optimal coating for this application is a multi-layer front-surface anti-reflection coating coupled with an infrared reflector coating on the rear surface. This produces an efficiency gain of ~3.5% over a standard encapsulated concentrator module, and includes the potential for system temperature reduction by reducing up to 80% of the excess energy impinging on the current-rich sub-cell.