International Business Machines Corporation

Egypt Nanotechnology Center

Mohamed Saad

Devendra K Sadana

Ahmed Abou-Kandil

Keith E Fogel

Jeehwan Kim

Osama Tobail

George Stojan Tulevski

Augustin J Hong

Hisham S Mohamed

Jee Hwan Kim

Mostafa M El-Ashry

Paul Michael Kozlowski

A Schottky-barrier-reducing layer is provided between a p-doped semiconductor layer and a transparent conductive material layer of a photovoltaic device. The Schottky-barrier-reducing layer can be a conductive material layer having a work function that is greater than the work function of the transparent conductive material layer. The conductive material layer can be a carbon-material layer such as a carbon nanotube layer or a graphene layer. Alternately, the conductive material layer can be another transparent conductive material layer having a greater work function than the transparent conductive material layer. The reduction of the Schottky barrier reduces the contact resistance across the transparent material layer and the p-doped semiconductor layer, thereby reducing the series resistance and increasing the efficiency of the photovoltaic device.

Photovoltaic devices with an interfacial band-gap modifying structure and methods for forming the same

A photovoltaic device includes a p-type layer. An intrinsic layer is formed directly on the p-type layer and includes an interface region extending into the intrinsic layer that includes a gradually decreasing band gap energy going from the p-type layer into the intrinsic layer formed by a graded deposition temperature. An n-type layer is formed directly on the intrinsic layer.

Temperature grading for band gap engineering of photovoltaic devices

A method for fabricating a photovoltaic device includes depositing a p-type layer at a first temperature and depositing an intrinsic layer while gradually increasing a deposition temperature to a final temperature. The intrinsic layer deposition is completed at the final temperature. An n-type layer is formed on the intrinsic layer.

A p-doped semiconductor layer of a photovoltaic device is formed employing an inert gas within a carrier gas. The presence of the inert gas within the carrier gas increases free hole density within the p-doped semiconductor layer. This decreases the Schottky barrier at an interface with a transparent conductive material layer, thereby significantly reducing the series resistance of the photovoltaic device. The reduction of the series resistance increases the open-circuit voltage, the fill factor, and the efficiency of the photovoltaic device. This effect is more prominent if the p-doped semiconductor layer is also doped with carbon, and has a band gap greater than 1.85V. The p-doped semiconductor material of the p-doped semiconductor layer can be hydrogenated if the carrier gas includes a mix of Hand the inert gas.

Solar cell employing an enhanced free hole density p-doped material and methods for forming the same

A hydrogenated thin film is formed in a controlled vacuum on a substrate by evaporating one or more solid materials and passing the resulting vapor and a hydrogen-containing gas into a space between two electrodes. One of the electrodes includes openings for allowing the vapor to enter the space. Plasma is generated within the space to cause dissociation of the hydrogen-containing gas and promote a reaction between the material(s) and hydrogen-containing gas.

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Mohamed Saad