Understanding Photovoltaic Energy Losses under Indoor Lighting Conditions.

The external luminescence quantum yield as a function of the solar cell current density when exposed to low indoor light was estimated based on absolute electroluminescence measurements and a self-consistent use of the electro-optical reciprocity relationship. By determining the luminescence yield at current densities corresponding to the cell operation at the maximum power point, we can compute energy losses corresponding to radiative and nonradiative recombination. Combined with other major energy losses, we can obtain a clear picture of the fundamental balance of energy within the cell when exposed to room light with a typical total illuminance of 1000 lx or less.