Growth and Fabrication of GaAs Thin-Film Solar Cells on a Si Substrate via Hetero Epitaxial Lift-Off

Seungwan Woo,Namgi Hong,Deahwan Jung,In-Hwan Lee,Jinho Bae,Taesoo Kim,Jihyun Kim,Jae-Hoon Han,Won Jun Choi,Rafael Jumar Chu,Geunhwan Ryu

doi:10.3390/app12020820

Abstract

We demonstrate, for the first time, GaAs thin film solar cells epitaxially grown on a Si substrate using a metal wafer bonding and epitaxial lift-off process. A relatively thin 2.1 μm GaAs buffer layer was first grown on Si as a virtual substrate, and a threading dislocation density of 1.8 × 107 cm−2 was achieved via two In0.1Ga0.9As strained insertion layers and 6× thermal cycle annealing. An inverted p-on-n GaAs solar cell structure grown on the GaAs/Si virtual substrate showed homogenous photoluminescence peak intensities throughout the 2″ wafer. We show a 10.6% efficient GaAs thin film solar cell without anti-reflection coatings and compare it to nominally identical upright structure solar cells grown on GaAs and Si. This work paves the way for large-scale and low-cost wafer-bonded III-V multi-junction solar cells.

Highlights

III-V multijunction solar cells have been the most efficient photovoltaic cells by overcoming the detailed balance limit of single-junction solar cells [1,2,3,4,5]
We demonstrate, for the first time, a thin-film GaAs solar cell grown on an Si wafer transferred to a polyimide film via a metal wafer bonding and epitaxial lift-off process
An inverted GaAs solar cell structure was grown on the GaAs/Si template and revealed a 10.6% 1-Sun efficiency without anti-reflection coating, demonstrating that a wafer bonding and epitaxial lift-off process is compatible with III-V solar cells hetero-epitaxially grown on Si substrates

Summary

Introduction

III-V multijunction solar cells have been the most efficient photovoltaic cells by overcoming the detailed balance limit of single-junction solar cells [1,2,3,4,5]. The monolithically integrated six-junction solar cell requires high material consumption and long epitaxial growth time for the three metamorphic graded buffers that are approximately ~5 μm thick in total. Four-junction solar cells fabricated by bonding an InGaP/GaAs dual-junction solar cell to an InGaAsP/InGaAs cell showed a record-breaking conversion efficiency of 44.7% under 297-Suns [9] This approach does not require lengthy and material-consuming growth of metamorphic graded buffers, it must consume two expensive III-V wafers, e.g., GaAs and InP wafers, to create one high efficiency multi-junction solar cell. The possibility of epitaxial lift-off of III-V solar cells grown on Si for wafer-bonded III-V multi-junction solar cells to reduce their manufacturing cost has not been explored. We believe that an optimized GaAs solar cell structure with InGaP window layer and back-surface field layer will boost the thin film GaAs solar cell performance further

Material Growth

Findings

Conclusions