Electroplating Solutions and Methods For Deposition of Group IIIA-VIA Films

Abstract

The embodiment described herein relate to pulse electroplating methods and solutions.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation-in-part of U.S. patent application Ser. No. 13 / 347,540 filed Jan. 10, 2012, which is a continuation of U.S. patent application Ser. No. 12 / 143,609 filed Jun. 20, 2008 (now U.S. Pat. No. 8,092,667), and is a continuation-in-part of U.S. patent application Ser. No. 13 / 306,863 filed Nov. 29, 2011, which is a continuation of U.S. patent application Ser. No. 12 / 123,372 filed May 19, 2008 (now U.S. Pat. No. 8,066,865), and is a continuation-in-part of U.S. patent application Ser. No. 12 / 121,687 filed May 15, 2008, and the entire contents of these applications are incorporated herein by reference.BACKGROUND[0002]1. Field of the Art[0003]This application relates to electroplating methods and solutions and, more particularly, to methods and electroplating solution chemistries for electrodeposition of Group IIIA-VIA layers on a conductive surface for solar cell applications.[0004]2. Description of the Related Art[...

AI Technical Summary

Benefits of technology

The patent text describes a method and solution for electroplating a thin film of a group of materials (IIIA-VIA) onto a surface of a base (IIIA material). The method involves forming a metal layer on the surface of the base, co-depositing materials to form a layer (IIIA-VIA) on the metal layer, and reacting the layers to form the absorber layer. The solution includes a solvent, a source of Ga, a source of Se, an anti-oxidant, an anti-flocculant, a pH adjuster, additives, and is adjusted to a pH of 0.5-13. The technical effects of this patent text include a more efficient method for plating thin films of IIIA-VIA onto a IIIA surface, and a solution that improves the quality and stability of the plated film.

Problems solved by technology

However, the cost of electricity generated using silicon-based solar cells is higher than the cost of electricity generated by the more traditional methods.

Such techniques may yield good quality absorber layers and efficient solar cells, however, they suffer from the high cost of capital equipment, and relatively slow rate of production.

Although it is possible to deposit In layers using various electroplating chemistries employing standard plating practices, unless these layers have sub-micron thickness and smooth morphology, they cannot be effectively used in thin film Group IBIIIAVIA compound solar cell fabrication.

However, electroplating a smooth Cu layer is relatively easy and the problem usually lies with Ga and In electrodeposition due to the tendency of these low melting, high surface tension elements forming droplets rather than continuous layers when deposited in thin film form.

This requirement presents many challenges for prior art In electroplating methods and chemistries.

As stated before, lack of planarity in sub-micron thick In and / or Ga-rich layers presents problems for application of such non-uniform layers to thin film solar cell manufacturing.

The quality of the overall solar cell would then suffer from the poor I-V characteristics of the separate solar cells formed on either one of the first and second regions.

However, such thick electroplated In layers are not useful for thin film solar cell fabrication since they yield CIGS absorbers that are too thick (thicker than about 3000 nm).

Thick absorber layers cause excessive stress and delamination from the base.

They also add to the cost of processing, which is not in line with the cost-lowering targets of thin film photovoltaics.

Using a 3000 nm thick CIGS absorber in a solar cell structure increases materials usage three time and wastes effectively 67% of the materials used in forming the CIGS absorber structure.

Images