Transparent conducting oxides (TCOs) are an increasingly important component of
photovoltaic (PV) devices, where they act as electrode elements, structural templates,
and diffusion barriers, and their work function controls the open - circuit device voltage.
They are employed in applications that range from crystalline - Si heterojunction with
intrinsic thin layer (HIT) cells to organic PV polymer solar cells. The desirable charac -
teristics of TCO ma te rials that are common to all PV technologies are similar to the
requirements for TCOs for flat - panel display applications and include high optical trans -
missivity across a wide spectrum and low resistivity. Additionally, TCOs for ter res trial PV
applications must use low - cost ma te rials, and some may require device - technology -
specific properties. We review the fundamentals of TCOs and the matrix of TCO
properties and proc essing as they apply to current and future PV technologies.