Epitaxial Reflector Structures for High Efficiency Quantum Well Solar Cells
Roger Welser1, Stephen Polly2, Ashok Sood1, Seth Hubbard2, Kyle Montgomery3
1Magnolia Optical Technologies, Inc., Woburn, MA, United States
/2RIT, Rochester, NY, United States
/3AFRL, Kirtland AFB, NM, United States

Nanostructured quantum well and quantum dot solar cells have been widely investigated as a means of extending infrared absorption and enhancing III-V photovoltaic device performance.  In particular, nanostructured solar cell device concepts have been leveraged to improve the performance of III-V solar cells by providing a means to improve current matching in multi-junction devices.  However, the real long-term benefit of nanostructured solar cells is that they provide a pathway to implement advanced single-junction photovoltaic device designs which can capture energy typically lost in traditional solar cells while maintaining application-specific advantages over multijunction counterparts.  To realize such high-efficiency single-junction devices, nanostructured device designs must be developed that maximize the open circuit voltage by minimizing both non-radiative and radiative components of the diode dark current.  Recently, a high efficiency (>26% AM1.5) single-junction quantum well solar cell has been demonstrated in a simple upright device structure employing a thin, strained InGaAs quantum well superlattice absorber in a heterojunction InGaP/GaAs diode.   In this work, we describe a broadband epitaxial reflector structure that can be readily incorporated into the previous 26% efficiency upright quantum well solar cell design to both enhance current collection and photon recycling.