Method for forming dendritic silver with periodic structure as light-trapping layer

Patent metadata

Field	Value
Publication number	US-9496444-B2
Application number	US-201514612948-A
Country	US
Kind code	B2
Filing date	Feb 3, 2015
Priority date	Oct 7, 2014
Publication date	Nov 15, 2016
Grant date	Nov 15, 2016

Abstract

The invention is related to a method for forming dendritic silver with periodic structure as light-trapping layer, includes these steps: form a photoresist layer on a conductive substrate, and at least two coherent light beams is provided in using a laser interference lithography apparatus, to form a plurality of particular patterns respectively on the setting-exposure positions of the conductive substrate in sequence till the particular periods pattern formed. Thereafter, form the dendritic silver nanostructure with period pattern on the conductive substrate via electrochemical process, wherein operating voltage is 2V or higher, and electrochemical reaction time is 10 sec or higher.

First claim

What is claimed is:

1. A method for forming dendritic silver with periodic structure as light-trapping layer, including the steps of:
(a) coating a photoresist layer on a side surface of a conductive substrate;
(b) using an interference lithography device to provide and project at least two coherent beams of specific shapes onto the conductive substrate for forming an exposure area of a specific interference pattern thereon, wherein the specific interference pattern is a one-dimensional interference pattern;
(c) adjusting and moving the at least two coherent beams to project upon another exposure area of the conductive substrate;
(d) repeating steps (b) to (c) for a plurality of times for forming a plurality of exposure areas of the specific interference pattern that are interconnected to one another into a pattern of a specific pitch period;
(e) performing an exposure lithography process;
(f) placing the conductive substrate and a conductor separately inside a container containing an electrolyte while connecting the conductive substrate and the conductor respectively to a cathode and an anode of a direct-current source for enabling an electrochemical reaction to grow a dendritic silver nano structure, wherein the electrolyte is a solution at least containing silver nitride, citric acid and a solvent, and an operating voltage of the direct-current source for enabling the electrochemical reaction is at least 2V, while a reaction time of the electrochemical reaction is lasting for at least 10 seconds; and
(g) performing an etching process upon the conductive substrate for removing any residue photoresist layer to form the dendritic silver nano structure with periodic patterns that is to be used as a light trapping layer.

2. The method of claim 1 , wherein the exposure lithography process is enabled by an interference lithography device of Mach-Zehnder architecture; and the at least two coherent beams of specific shapes are coherent beams of uniform intensity and with a wavelength of 445 nm.

3. The method of claim 1 , wherein the at least two coherent beams are projected in directions allowing a specific included angle sandwiched there between, while allowing the specific included angle to be adjustable.

4. The method of claim 1 , wherein the step (b) further includes a step of: rotating or moving the conductive substrate and correspondingly adjusting the specific included angle for forming a two-dimensional interference pattern in the exposure area.

5. The method of claim 1 , wherein the specific pitch period of the pattern formed in the light trapping layer with the dendritic silver nano structure with periodic pattern is ranged between 50 nm to 10000 nm, while allowing the size of the dendritic silver nano structure to be ranged between 100 nm to 5000 nm.

6. The method of claim 1 , wherein the dendritic silver nano structure is formed in a shaped selected from the group consisting of: a shrub-like formation and a branch-like formation.

7. The method of claim 1 , further comprising a step (h) of:
performing a deposition process upon the conductive substrate for forming sequentially an a-Si photoelectric conversion layer containing at least one p-i-n semiconductor structure, a transparent conducting layer and an electrode layer on the light trapping layer so as to form a thin-film solar cell of dendritic silver nano structure with periodic pattern.

8. The method of claim 1 , wherein the conductive substrate is a substrate selected from the group consisting of: an ITO glass substrate, a silver-containing substrate and a stainless steel substrate.

9. The method of claim 1 , wherein the conductor is a bar or a panel that is made of platinum.

10. The method of claim 1 , wherein the electrolyte contains at least one solvent, and the at least one solvent is selected from the group consisting of: a deionized water and a distilled water.

11. The method of claim 1 , wherein the proportion of the silver nitride and the citric acid is defined by a mole ratio selected from the group consisting of: 0.8˜0.9:1, 0.9˜1:1, 0.9˜1:1, 1˜1.1:1, and 1.1˜1.2:1.

12. The method of claim 7 , wherein the transparent conducting layer is made of a material selected from the group consisting of: AZO, ITO, and IGTO.

13. The method of claim 7 , wherein the deposition process is a process selected from the group consisting of: a PVD process, a CVD process and the combination of the two.

Assignees

• Iner Aec Executive Yuan

Inventors

• Jan Der-Jun
• Lo Shih-Shou
• Lai Wei-Hsun
• Hsu Wei-Hsiu

Classifications

• H01L31/056 Primary

  Electricity · mapped topic

• H01L31/202

  Electricity · mapped topic

• H01L31/1884

  Electricity · mapped topic

• H10F77/1692

  the films including only Group IV materials · CPC title

• H10F71/138

  Manufacture of transparent electrodes, e.g. transparent conductive oxides [TCO] or indium tin oxide [ITO] electrodes · CPC title