Emitter controlled SiN _x-free crystalline Si solar cells with a transparent conducting oxide film

A transparent conducting oxide (TCO) layer was applied in crystalline Si (c-Si) solar cells without use of the conventional SiN _x-coating. A high quality indium-tin-oxide (ITO) layer was directly deposited on an emitter layer of a Si wafer. Three different types of emitters were formed by controlling the phosphorous diffusion conditions. A light-doped emitter forming a thinner emitter junction showed an improved photoconversion efficiency of 14.1% compared to the value of 13.2% for a heavy-doped emitter. This was induced by lower recombination within the narrower depletion region of the light-doped emitter. As for the electrical aspect, the ITO layer serves as an efficient electrical conductor and thus relieves the burden of high contact resistance of the light-doped emitter. From the aspect of light management, the intermediate refractive index of ITO is effective at reducing the light reflection, leading to an enhanced carrier generation in Si absorbers.