Dr. Warren is a staff scientist in the High Efficiency Crystalline Photovoltaics group at NREL.

Her research is focused on the heteroepitaxy of III-V materials on silicon and other low-cost substrates, nanoimprint lithography, and the simulation and fabrication of high efficiency tandem solar cells and modules. She is interested in understanding how nanoscale surface control can influence the nucleation and coalescence of heteroepitaxial films. 

Her work on three-terminal tandem solar cells based on bottom cells with interdigitated back contacts is a compelling platform for tandem cell integration because it enables the same robust performance of individually operated subcells under varying illumination conditions, but does not require lateral current extraction between the cells, which can become challenging when scaling devices to large areas.

Warren has worked on a variety of collaborative projects with universities and mentored several graduate students and undergraduate interns, winning multiple mentoring awards. Her prior work at NREL included the photoelectrochemical characterization of new semiconductor materials and the development and testing of solar thermoelectric generators using NREL’s High Flux Solar Furnace. Before joining NREL, she completed her PhD at Caltech, studying the growth and energy conversion properties of silicon microwire arrays as well as the electrochemical characterization of semiconductor photocathodes and catalysts for solar fuel generation.

Research Interests

Heteroepitaxy/integration of dissimilar semiconductor materials

High-efficiency tandem and multijunction solar cells

Nanoimprint lithography

TCAD device simulation of solar cells

Module-level integration of tandem solar cells

Photoelectrochemistry of new semiconductor materials

Education

BS, Chemical Engineering, Cornell University

MPhil, Engineering for Sustainable Development, University of Cambridge

PhD, Chemical Engineering, California Institute of Technology

Featured Work

“Back‐contacted bottom cells with three terminals: Maximizing power extraction from current‐mismatched tandem cells,” Progress in Photovoltaics (2019)

“Perspective: Fundamentals of coalescence-related dislocations, applied to selective-area growth and other epitaxial films,” APL Materials (2018)

“GaAs solar cells on nanopatterned Si substrates,” Journal of Photovoltaics (2018)

"Maximizing tandem solar cell power extraction using a three-terminal design," Sustainable Energy & Fuels (2018)

“Solar energy conversion properties and defect physics of ZnSiP₂,” Energy & Environmental Science (2016)

“Growth of APD-free GaP on Si substrates by MOCVD using an in-situ AsH₃ surface preparation, ”Applied Physics Letters (2015)

"Silicon Microwire Arrays for Solar Energy-Conversion Applications," The Journal of Physical Chemistry C (2013)

"Hydrogen-Evolution Characteristics of Ni-Mo-Coated, Radial Junction, n+p-silicon Microwire Array Photocathodes," Energy & Environmental Science (2012)

"Energy-Conversion Properties of Vapor-Liquid-Solid-Grown Silicon Wire-Array Photocathodes," Science (2010)

"Solar Water Splitting Cells," Chemical Reviews (2010)

“Enhanced absorption and carrier collection in Si wire arrays for photovoltaic applications,” Nature Materials (2010)