Abstract

A new irradiance adjustment system for the light source named “Programmable Reference cell system for Irradiance adjustment by Spectral Measurement ( PRISM )” has been developed for photovoltaics evaluation. It can be applied for various kinds of solar cells and illumination conditions without the preparation of conventional reference cells. This system consists of a device for absolute spectral responsivity measurements, that is, the spectral responsivity unit, and a device for irradiance adjustment of the light source, that is, the spectral reference cell. First, the short circuit current of the target solar cell ( I _ref) is calculated by convolution of the absolute spectral responsivity with the spectral irradiance under STC ( AM 1.5 G, 1 kW/m², 25°C) as defined in IEC 60904‐3. The spectral irradiance of the light source is then adjusted for I–V measurements so that the short‐circuit current of the spectral reference cell ( I _cal), calculated by convolution of the absolute spectral responsivity with the spectral irradiance of the light source, agrees with I _ref. The difference between I _ref and the short circuit current, as determined at an internationally recognized test center under STC , was within ±2% for crystalline silicon solar cells and ±3% for organic solar cells. The difference between I _cal and the short‐circuit current measured under a solar simulator or LED in which the irradiance was adjusted by this system was within ±4% when the irradiance was higher than 4 W/m².

A newly developed irradiance adjustment system for the light source to assist in photovoltaics evaluation was found to be applicable for any type of solar cell under various irradiation conditions without the preparation of a reference cell as defined in IEC 60904. The difference between the short‐circuit current calculated from the absolute spectral responsivity and that measured under a light source with irradiance adjusted by this system (Δ I _sc) was found to be within ±5%.