Transparent Window Layers for n-CdTe Solar Cells

Polycrystalline n-type CdTe:In films were deposited by the elemental vapor transport (EVT) process. An appropriate p-type window layer is critical for the optimal performance of n-CdTe solar cells. This work applied ZnSe and Te-rich ZnTe thin films as p-type partners for n-type In-doped CdTe solar cells. ZnSe films deposited at a higher substrate temperatures exhibit higher SR in the short-wavelength region, indicating improved interface quality. Te-rich ZnTe thin films with various thicknesses and a passivation Al<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> layer at the n-CdTe/p-ZnTe interface were also investigated. Al<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> was found to passivate the CdTe/ZnTe interface. Devices with a single cycle of Al<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> exhibit superior passivation performance than devices with multiple cycles of Al<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> layer. The passivation effect is more significant for Te-rich ZnTe film with a thickness of 200Å compared to those with a thickness of 500Å.