Method and apparatus for annealing micro-scale or macro solar cells that can contain lithium or hydrogen. Heaters, a current that is applied in forward or reverse direction, or open-circuiting the cells are used optionally with a laser or other light source to increase the temperature of the cells to perform periodic anneals to recover energy conversion efficiency lost due to environmental conditions such as radiation damage and maintain desired operational conditions. Larger amounts of additional energy are harvested with the improved efficiency of the cells. Illuminating the cells with specific wavelengths of light can enhance the diffusion of the lithium or hydrogen, or their binding and unbinding from dopants or defects, in the silicon lattice. The lithium or hydrogen can diffuse into the cells via their inclusion in the polysilicon layer forming a tunneling oxide passivated contact. Dopants in the silicon can reduce annealing time and temperature.