Electrodeposition of photoactive silicon films for low-cost solar cells

Here we demonstrate progress on electrodeposition of photoactive silicon films from an environmentally friendly molten CaCl₂ electrolyte, which is the first step of a new route to a practical low-cost silicon solar cell. We report electrodeposition of severalmicron thick silicon films on a graphite substrate in a bath of molten CaCl₂ containing SiO₂ nanoparticles. The best silicon deposits was obtained at 6 mA/cm² for 1 hour in molten CaCl₂ containing 0.3 M SiO₂ nanoparticles, at 850° C. The main impurities are Al, Mg, Ca, Na. A photoelectrochemical method was demonstrated as a reliable and sensitive measurement for testing the quality of the silicon film. The as-deposited film exhibits 31% of the photocurrent response of a commercial p-type wafer. A comparison of graphite and silver substrates is presented, and the remaining problems are discussed.