Enhanced performance of solar cells with anti-reflection layer fabricated by nano-imprint lithography

Because of increase in demand for clean energy sources, photovoltaic device is becoming more important as a new power plant. To replace fossil fuels with photovoltaics, generating electricity with solar cells should meet cost effectiveness and high efficiency. An anti-reflection technique is one of the effective methods to achieve high efficiency. To reduce the reflection at the surface of concentrated photovoltaic device, a nanometer scale dot-pattern array was formed on the surface of GaInP/Ga(In)As/Ge solar cells by nano-imprint lithography. Since this nano-pattern is smaller than the wavelength of visible light, the effective refractive index near the surface changes gradually. Thus, the reflection of the light at the surface with moth-eye structure can be effectively reduced for overall spectral region. As a result, a solar cell with the moth-eye pattern as an anti-reflection layer showed lower reflectance and enhanced total conversion efficiency, compared to a solar cell without a moth-eye patterned layer. The patterned solar cell was characterized using UVvis spectrophotometer, atomic force microscope (AFM) and scanning electron microscope (SEM), and its total conversion efficiency was measured by solar simulator.