Nanostructured window layer in solar cells

Patent metadata

Field	Value
Publication number	US-2016293787-A1
Application number	US-201314442133-A
Country	US
Kind code	A1
Filing date	Nov 12, 2013
Priority date	Nov 12, 2012
Publication date	Oct 6, 2016
Grant date	—

Abstract

A solar cell has a nanostructured window layer with planar p-n junction geometry. Preferably, metal grid mesas are used to provide lateral conductance and good electrical contacts. In addition to carrier confinement and lateral conductance, this window layer can also provides a broadband angle-independent antireflection function. This structure enhances both the optical and electrical properties in a solar cell, leading to higher J sc , V oc , FF (fill factor) and efficiency. The absorption in the window layer is partially converted to photocurrent, which to some extent compensates for the self-absorption loss due to its greater thickness. This design can eliminate the need for a separate anti-reflection coating.

First claim

1 . A solar cell comprising:
a semiconductor active region, wherein optical absorption in the active region provides electrical charge carriers; a semiconductor window layer disposed on the active region, wherein light incident on the active region passes through the window layer, and wherein the window layer is electrically conductive; wherein a bottom surface of the window layer and a top surface of the active region meet at a substantially planar interface; wherein a top surface of the window layer opposite the bottom surface of the window layer includes nano-structures; wherein the window layer has a different composition than the active region; and wherein a band gap of the window layer is greater than a band gap of the active region at the interface.

2 . The solar cell of claim 1 , wherein the active region and the window layer both comprise one or more compound semiconductors.

3 . The solar cell of claim 1 , wherein the active region comprises one or more p-n junctions.

4 . The solar cell of claim 1 , wherein both the active region and the window layer are single-crystal or poly-crystalline.

5 . The solar cell of claim 1 , wherein the top surface of the window layer comprises one or more shapes selected from the group consisting of: nano-cones, nano-pyramids and nano-domes.

6 . The solar cell of claim 1 , wherein the window layer provides optical anti-reflection due to the included nano-structures.

7 . The solar cell of claim 1 , wherein no anti-reflection coating is disposed on the top surface of the window layer.

8 . The solar cell of claim 1 , wherein the top surface of the window layer further includes planar regions for making electrical contact.

9 . The solar cell of claim 8 , wherein the planar regions are configured as a grid having cells that include the nano-structures.

10 . The solar cell of claim 1 , wherein the window layer has an indirect band gap.

Assignees

• Univ Leland Stanford Junior

Inventors

• Liang Dong
• Kang Yangsen
• Huo Yijie
• Harris Jr James S

Classifications

• H10F77/703 Primary

  of the semiconductor bodies, e.g. textured active layers · CPC title

• H10F77/315

  the coatings being antireflective or having enhancing optical properties · CPC title

• H10F77/215

  Geometries of grid contacts · CPC title

• H10F10/163

  comprising only Group III-V materials, e.g. GaAs/AlGaAs or InP/GaInAs photovoltaic cells · CPC title

• H10F10/162

  comprising only Group II-VI materials, e.g. CdS/CdTe photovoltaic cells · CPC title