Recent trends of patents on front TCOs for highly efficient thin-film Si photovoltaic devices

The recent trends of US patents on the front transparent electrode of thin-film silicon (Si) photovoltaic (PV) devices are reviewed. The various transparent conductive oxide (TCO) materials have been invented to satisfy a multifunctional prerequisite for the front electrode: high electrical conductivity, high optical transparency, effective light trapping, anti-reflection effect, and diffusion barrier. The recent surge of filed patents reflects the great importance of the front TCO technology for high efficiency thin-film Si PV devices. Among the TCO materials, properties of commercially available F-doped tin oxide (SnO2:F)-coated glass substrates are compared. SnO2:F-coated glass substrates share 20-30% of the cost for production of thin-film Si PV modules - evaluated values from mass production at KISCO. Therefore, the cost and technological innovation must be established for cost-effective mass production of large-area thin-film Si multijunction PV modules.