An energy conversion device comprising a first electrically conductive layer, a mesoporous oxide layer contiguous with the first electrically conductive layer and comprised of volcanic ash particles and photoactive dye molecules adsorbed on the ash particles, an electrolyte layer contiguous with the mesoporous oxide layer and comprised of a redox mediator, a catalyst layer comprised of an electrically conductive catalyst material, and a second electrically conductive layer contiguous with the catalyst layer. The electrically conductive catalyst material may be graphene, graphite, platinum, or carbon. The device may be further comprised of a light transmissive substrate contiguous with the first electrically conductive layer. The mesoporous oxide layer may be further comprised of titanium dioxide particles. The volcanic ash may comprise a mixture of particles from different indigenous sources of volcanic ash. Methods of fabrication of the device and conversion of light energy to electrical energy using the device are also disclosed.