Ohmic contact of thin film solar cell

Abstract

A chalcogen-resistant material including at least one of a carbon nanotube layer and a high work function material layer is deposited on a transition metal layer on a substrate. A semiconductor chalcogenide / kesterite material layer is deposited over the chalcogen-resistant material. The carbon nanotubes, if present, can reduce contact resistance by providing direct electrically conductive paths from the transition metal layer through the chalcogen-resistant material and to the semiconductor chalcogenide material. The high work function material layer, if present, can reduce contact resistance by reducing chalcogenization of the transition metal in the transition metal layer. Reduction of the contact resistance can enhance efficiency of a solar cell including the chalcogenide semiconductor material.

Description

BACKGROUND[0001]The present disclosure relates to contact structures, and particularly to low resistance contact structures between a transition metal layer and a semiconductor material, and methods of manufacturing the same.[0002]Many thin film solar cells include a chalcogenide in an absorber layer. The chalcogenide can be a chalcopyrite such as CuIn(S,Se)2 (CIS) and CuInGaSe2 (CIGS), kesterite (Cu2(Zn, Fe) Sn (Se,S)4, Ga(S,Se), GaTe, GaAs, In2(S,Se)3, and InTe, InP, CdTe, Cd(S, Se), ZnTe, Zn3P2, Pb(Se,S), Zn(S, Se), W(S,Se)2, Bi2S3, Ag2S, NiS, ZnO, Cu2O, CuO, Cu2S, FeS2. These solar cells have been fabricated using different process like PVD, CVD, solution processes, or electrochemical deposition process.[0003]For example, in thin films solar cells, a back contact material such as molybdenum is deposited on a dielectric substrate. Absorber layers, such as a stack of a p-type semiconductor material and an n-type semiconductor material, are deposited on the back contact material. W...

AI Technical Summary

Benefits of technology

This patent describes a method of making a material that can resist damage caused by chalcogens, which are materials that can damage a semiconductor material. The method involves depositing layers of carbon nanotubes and a material with a high work function on top of a transition metal layer. This helps to reduce contact resistance and the formation of damaging compounds in the material. By doing this, the efficiency of solar cells made with the chalcogens can be improved.

Problems solved by technology

Formation of excess molybdenum disulfide between a molybdenum layer and the absorber layer may cause a poor ohmic contact between the molybdenum layer and the absorber layer.

Further, due to high compressive stress developed in the absorber layer, gaps can be formed within the molybdenum sulfide layer, and significantly degrade the electrical contact between the absorber layer and the molybdenum layer.

By effectively reducing the total contact area between the absorber layer and the molybdenum layer, such gaps increase the series resistance of a solar cell, and reduces the efficiency of the solar cell.

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