Not sure if this is the right section for this, I apologize in advance. I have a project to do and my goal is to measure the efficiency of a solar cell INDIRECTLY. I am not sure how to do that. The equation for the efficiency of a solar cell is η = P/E*A. Where P is the cells power output (W), E is the irradiance (W/m^2) and A is the surface area of the cell (m^2). The only thing I can think of is using a pyranometer to measure irradiance, and digital multimeter to measure power, but these aren't really indirect. Can someone please help? Thanks.