Granted Patent B2

US 12,563,857 · App. 18/372,567 · Granted Feb 24, 2026

Inventors: Dan Damjanovic (Boise, ID); Feng Liao (Perrysburg, OH); Rick Powell (Ann Arbor, MI); Rui Shao (Sylvania, OH); Jigish Trivedi (Pleasanton, CA); Zhibo Zhao (Novi, MI)

Assignee: First Solar, Inc.

H10F77/1237H10F10/162H10F71/1253H10F71/128Y02E10/543Y02P70/50

Abstract

Claims (20)

1 . A method for forming a photovoltaic structure, comprising:

providing a substrate structure comprising a transparent conductive oxide (TCO) layer;

depositing a layer comprising cadmium, selenium, and tellurium over the substrate structure, wherein the step of depositing the layer comprising cadmium, selenium, and tellurium, includes: sequentially depositing a CdSe layer over the substrate structure, followed by depositing a CdTe layer over the CdSe layer; and

alloying the layer comprising cadmium, selenium, and tellurium, whereby an absorber layer is formed over the substrate structure, wherein:

a p-n junction is formed between the absorber layer and the substrate structure, the absorber layer is p-type,

the absorber layer is composed of cadmium selenide telluride, wherein a concentration of selenium varies through a thickness of the of the absorber layer,

the absorber layer has higher selenium concentration adjacent to the substrate structure and decreasing through a thickness of the absorber layer, and

a compositional ratio of Se throughout the absorber layer is less than or equal to about 25 at. %, wherein the compositional ratio of Se is determined by comparing the number of selenium atoms with a total sum of selenium and tellurium atoms in the absorber layer.

2 . The method of claim 1 , wherein the step of depositing the layer comprising cadmium, selenium, and tellurium, comprises: evaporating cadmium selenide powder and cadmium telluride powder, and sequentially depositing the CdSe layer over the substrate structure, followed by depositing the CdTe layer by vapor transport deposition.

3 . The method of claim 1 , wherein the depositing step further comprises: including a dopant in the layer comprising cadmium, selenium, and tellurium.

4 . The method of claim 1 , wherein the alloying step occurs after the step of depositing the layer comprising cadmium, selenium, and tellurium over the substrate structure.

5 . The method of claim 1 , further comprising an activation step of contacting a material containing chlorine to the absorber layer, and annealing the absorber layer.

6 . The method of claim 5 , wherein the activation step comprises contacting the CdSeTe layer with CdCl 2 and another material containing chlorine.

7 . The method of claim 1 , further comprising an activation step of heating the absorber layer in contact with CdCl 2 at a temperature in a range from 420° C. to 460° C. for a duration in a range from five minutes to sixty minutes.

8 . The method of claim 1 , wherein the substrate structure does not include a window layer comprising CdS, and wherein the substrate structure does not include a window layer comprising CdSSe.

9 . The method of claim 1 , further comprising: forming a back contact over the absorber layer, wherein the back contact comprises an ohmic electrode comprising an electrically conductive material.

10 . The method of claim 1 , further comprising:

forming a back contact layer over the absorber layer, whereby the absorber layer is between the TCO layer and the back contact layer; and wherein a concentration of Se in the absorber layer is greater near the TCO layer than the back contact.

11 . The method of claim 1 , wherein the step of forming the CdSeTe layer includes: co-evaporating cadmium telluride powder and cadmium selenide powder.

12 . The method of claim 1 , wherein the step of forming the CdSeTe layer includes: evaporating a powder alloy comprising cadmium, and at least one of tellurium or selenium, wherein a composition of the powder is tailored to deposit the CdSe x Te 1−x layer, with a compositional gradient of Se.

Assignments (3)

Continuity (7)

References Cited (195)