Skip Navigation

Low-Cost, Manufacturable, 6-Inch Wafer Bonding Process for Next-Generation 5-Junction IMM+Ge Photovoltaic Devices, Phase II

Completed Technology Project

Project Introduction

To continue the trend towards ever more efficient photovoltaic devices, next-generation multi-junction cells will be based on increasingly complex structures. These structures will require the ability to join two or more independently grown epitaxial structures together via wafer bonding which is a complicated process to include in a high-volume manufacturing environment using conventional wafer fusion techniques. Additionally, metamorphic material is very difficult to bond due to the inherent roughness of the surface. We propose the development of a bonding process based on an epoxy interface with an embedded metallic grid to provide electrical conductivity across the bonded interface. This process is expected to be low-cost, compatible with metamorphic material and high-volume manufacturing, and readily scalable to 6-inch or larger substrates. It will be an enabling technology for next-generation, five- and six-junction solar cells with 1-sun AM0 efficiency exceeding 37% in high volume production. An example device structure that can benefit from the proposed wafer bonding technique is a six-junction solar cell. This six-junction device is composed of two triple-junction stacks, one of which is grown on a GaAs substrate while the other is grown on an InP substrate. The two triple-junction stacks must be bonded together to form the final six-junction device. The epoxy-bonding process proposed here will allow this bonding to be accomplished reliably on large-area substrates. This is essential for turning this structure into a practical, manufacturable, commercial product. When coupled with MicroLink Device's proprietary epitaxial lift-off (ELO) technology which allows for reuse of both the GaAs and InP substrates, devices based on this six-junction architecture could potentially be manufactured for less than $170/W in sufficient volume to serve near-term applications. This structure is expected to yield 40% efficiency under AM0 illumination. More »

Anticipated Benefits

Primary U.S. Work Locations and Key Partners

Share this Project

Organizational Responsibility

Project Management

Project Duration

Technology Maturity (TRL)

Technology Areas

Light bulb

Suggest an Edit

Recommend changes and additions to this project record.