An apparatus, system, and method are disclosed for restoring efficiency of a photovoltaic cell. An illumination module illuminates photovoltaic cells so the cells receive a time integrated irradiance equivalent to at least 5 hours of solar illumination. After illumination, an annealing module anneals the photovoltaic cells at a temperature above 90 degrees Celsius for a minimum of 10 minutes. In one embodiment, the illumination module illuminates the photovoltaic cells for a time integrated irradiance equivalent to at least 20 hours of solar illumination. In another embodiment, the illumination module illuminates the photovoltaic cells for a time integrated irradiance equivalent to at least 16 hours of solar illumination while being heated to at least 50 degrees Celsius. In another embodiment, a solar concentrator irradiates the photovoltaic cells in sunlight for at least 10 hours and increases the irradiance of solar illumination on the cells by a factor of 2 to 5.