About

The McGehee Research Group at the University of Colorado Boulder is composed of members from various academic backgrounds including Physics, Chemistry, Materials Science, and Chemical Engineering. This diverse composition facilitates opportunities for collaboration within the group and provides different perspectives to conduct research. Professor Michael D. McGehee is associated with this group and is based in the Department of Chemical and Biological Engineering. His office is located in the Sustainability, Energy and Environment Community (SEEC) at N360N, with a physical address at 4001 Discovery Drive, Boulder, CO. His contact information includes an email address (michael.mcgehee@colorado.edu) and a phone number (303) 492-2063. The group's focus on interdisciplinary research aims to advance knowledge in energy, sustainability, and environmental fields.

Research topics

• Materials science
• Chemistry
• Computer Science
• Optoelectronics
• Inorganic chemistry
• Electrical engineering
• Nanotechnology
• Engineering
• Artificial Intelligence
• Systems engineering
• Business
• Crystallography
• Metallurgy
• Engineering physics
• Reliability engineering
• Telecommunications
• Risk analysis (engineering)
• Composite material
• Organic chemistry
• Data science
• Psychology
• Software engineering
• Chemical engineering

Selected publications

• Photophysical Properties and Phase Behavior of Ultrawide Photovoltaic Bandgap Cesium–Lead-Based Triple Halide Perovskites

  Chemistry of Materials · 2026-01-05 · 1 citations

  articleSenior authorCorresponding

  Metal halide perovskite films in the top cell of triple-junction tandems require bandgaps around 2.0 eV to achieve current matching, assuming that the middle absorbing layer is the commonly used FAPbI3 composition and the bottom cell has a bandgap around 1.1 eV. Unfortunately, mixed organic/inorganic metal halide perovskites that have the necessary Br content to reach a bandgap of 2.0 eV segregate into iodine-rich and bromine-rich phases under illumination, limiting their obtainable voltage. Previous reports have shown improved photostability using either Cs-based inorganic compositions or Cl incorporation on the X-site. Here, we investigate the inorganic triple halide compositional space CsPb(I1–x–yBryClx)3 where bandgaps near 2.0 eV are expected based on the knowledge that CsPbI2Br has a bandgap of 1.90 eV. Incorporation of Cl occurs readily for x ≤ 0.07–0.10 within perovskites with a Br content of 0.3 ≤ y ≤ 0.42. When x >0.1, X-ray diffraction and photoluminescence (PL) measurements indicate that multiple compositional phases form. We hypothesize that the variable sizes of the three halide ions are not supported within the rigid Cs lattice, resulting in the formation of multiple compositional phases. The photoluminescence quantum yield of the single-phase compositional space─CsPb(I1–x–yBryClx)3 where x ≤ 0.07─was typically 0.001–0.004%, most likely as a result of a high defect density, including mobile iodine species. PL light-soaking measurements of many perovskite compositions with bandgaps in the range of 1.89–2.05 eV demonstrate that phase segregation occurs when initial bandgaps are above 1.95 eV regardless of halide content: indicating further iodide oxidation and corresponding migration under illumination. The conclusion is that further compositional or additive engineering is necessary for the development of inorganic triple halide compositions that accomplish the elusive goal of fabricating high-quality and photostable 2.0 eV films for use in multijunction tandems.

  PublisherDOI

• Evaluation of smart glazing properties for net positive windows in commercial buildings

  Energy and Buildings · 2026-02-11

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  PublisherDOI

• Molecular Order and Disorder in the Semicrystalline Conjugated Polymer PBTTT and Donor–Acceptor Interactions in Bulk Heterojunction PBTTT:Fullerene Blends

  Macromolecules · 2025-07-28 · 2 citations

  article

  The compositions and structures of the conjugated polymer poly(2,5-bis(3-hexadecylthiophen-2-yl)thienothiophene) (PBTTT-C16) are quantitatively measured and distinguished for the crystalline and disordered regions, as well as the intermolecular interactions between phenyl-C71-butyric acid methyl ester (PC71BM) and PBTTT moieties in bulk heterojunctions (BHJs). For PBTTT-C16, the long-range (>10 nm) crystalline order of lamellae is established by two-dimensional (2D) grazing-incidence small-angle X-ray scattering (GISAXS), while short-range (<1 nm) structures are characterized by using solid-state nuclear magnetic resonance (NMR) spectroscopy. In particular, 2D 1H{1H} double-quantum and 13C{1H} heteronuclear correlation NMR spectra reveal distinct intensity correlations for PBTTT-C16 that provide direct evidence for the presence of regions with well-ordered π–π-stacked conjugated backbones and interdigitated alkyl side chains, stacked backbones and disordered side chains, and amorphous regions of PBTTT-C16. Good agreement is found between the X-ray diffraction (XRD) and solid-state NMR analyses for 1H–1H distances between interlayer aromatic moieties (3.7 Å from XRD, 3.6 Å from 2D 1H{1H} NMR) and for the intermolecular C–H distances between the aromatic hydrogen atoms and terminal methyl carbon atoms (3.3–3.4 Å from XRD, 3.3 Å from 2D 13C{1H} NMR) in the crystalline regions. A larger mean 1H–1H distance of >3.8 Å between interlayer PBTTT backbones in less-ordered and disordered regions is determined by NMR, which is otherwise difficult to assess by XRD analyses alone. Combined solid-state NMR and density functional theory (DFT) results corroborate that the conjugated PBTTT-C16 backbones adopt nearly coplanar conformations in the ordered regions with a distribution of dihedral angles bisecting the thienothiophene moieties in the amorphous regions. The polar five-membered ring of the C70 fullerene in the PBTTT-C16:PC71BM blend was found to interact strongly with the aromatic thienothiophene protons of the semiconducting polymer, causing a strong π–π overlap of distinct moieties of the fullerene and polymer chain. The relative displacements of 1H chemical shifts by local ring currents and measurements of homonuclear 1H dipole–dipole couplings allow the molecular proximities between specific chemical moieties of the electron-donating PBTTT and the electron-accepting PC71BM species in the bimolecular BHJs to be established.

  PublisherDOI

• Applying in situ bias during TOF–SIMS analysis to investigate ion migration in perovskite devices

  MRS Communications · 2025-06-30

  articleOpen access

  Abstract An in situ electrical bias was placed on a perovskite device through the device thickness while under investigation with time-of-flight secondary ion mass spectrometry. The applied bias resulted in an observed reversible migration of halide and lithium ions on the timescale of minutes. The results show a framework that can be used for further study of ion migration in perovskite materials and devices. Graphical abstract

  PublisherOA PDFDOI

• How non-ohmic contact-layer diodes in perovskite pinholes affect abrupt low-voltage reverse-bias breakdown and destruction of solar cells

  Joule · 2025-08-25 · 13 citations

  articleSenior author
  PublisherDOI

• Toward Fullerene-Free PIN Perovskite Solar Cells

  ACS Energy Letters · 2025-11-18 · 3 citations

  articleOpen access

  bilayers and nonfullerene acceptor-based ETLs. Despite successes, fullerenes remain the de facto ETLs for perovskites. Drawing lessons from organic photovoltaics, where it took decades to transition from fullerenes to more broadly available and efficient materials, we explore pathways to accelerate the development and adoption of fullerene-free ETLs. This requires understanding the similarities and differences between organic and perovskite solar cells, which will necessitate carefully designing fullerene replacements with both, high efficiency and also, critically, durability under operation. Here, we incorporate literature data to facilitate comparisons, and independently conduct fracture energy measurements for alternative ETL configurations to motivate their adoption.

  PublisherDOI

• Enhancing the Cycle Life of Reversible Silver Electrodeposition Optical Devices with Durable Gold Seed Particles

  ACS Applied Materials & Interfaces · 2025-12-04 · 1 citations

  articleSenior authorCorresponding

  Devices with light transmission that can be adjusted by reversible metal electrodeposition (RME) can be used for energy-efficient dynamic windows, eyewear, thermal camouflage, and displays. Ag RME devices with resting stability exceeding 24 h and durability of more than 7500 cycles have been reported. However, Ag RME devices employing ITO electrodes modified with Pt nanoparticles exhibit progressively slower tinting during cycling. Here, we identify the origin of this degradation, showing that Pt nanoparticles undergo oxidation during repeated operation when stripping Ag from the ITO surface. We further demonstrate that modifying ITO with durable Au nanoparticles preserves the window's switching speed and maintains the consistency of the Ag film transmission spectrum over cycling.

  PublisherDOI

• Dynamic windows based on reversible silver electrodeposition with improved resting stability and cyclability

  Cell Reports Physical Science · 2025-04-28 · 5 citations

  articleOpen accessSenior author
  PublisherDOI

• Quantifying energy benefits from window improvement strategies for commercial buildings

  Energy and Buildings · 2025-08-05 · 5 citations

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  PublisherDOI

• A Stress-Diffusion-Stability Framework Enables Ambient Fabrication of Hybrid Perovskites with Extended Environmental Stability

  ChemRxiv · 2025-12-30

  article

  Hybrid perovskites have become a leading candidate for next-generation photovoltaic applications, but they still suffer from several intrinsic and extrinsic sources of instability. Residual tensile stress has emerged as a major source of extrinsic instability, as it originates from thin film fabrication and choice of substrate. Here, we propose an experimentally validated mechanical stress-diffusion framework which links dynamic stress relaxation behavior of perovskites to vacancy-mediated grain boundary (GB) halide diffusional, namely, Coble creep. Using temperature-dependent in situ analysis of stress and strain relaxation across the perovskite composition, we quantitatively link these mechanisms. We extend this framework to link these mechanisms to material stability in the context of ambient manufacturing in the presence of humidity. The Coble creep mechanism is circumvented by the fast diffusion of water molecules, with potentially severe impact on material degradation. We show how pre-relaxation of perovskite films in a dry environment (0% RH and N2) extends lifetime from &lt;100 hours to &gt;1,000 hours in moderately humid air by removing the driving force for moisture uptake. This work identifies the fundamental mechanisms of stress relaxation and diffusion responsible for moisture uptake and proposes stress relaxation approaches which facilitate ambient manufacturing of existing materials and fabrication approaches under moderate humidity conditions.

  PublisherDOI

Recent grants

• Reversible Metal Electrodeposition for Modulating Light

  NSF · $484k · 2021–2024

Frequent coauthors

• Michael F. Toney

  89 shared

• Caleb C. Boyd

  Stanford University

  73 shared

• Jean M. J. Fréchet

  72 shared

• Tomas Leijtens

  Swift Solar (United States)

  54 shared

• Christoph J. Brabec

  Forschungszentrum Jülich

  53 shared

• Kevin A. Bush

  51 shared

• Yongfang Li

  Institute of Chemistry

  49 shared

• Joseph M. Luther

  National Renewable Energy Laboratory

  48 shared

Education

• Ph.D.

  University of California at Santa Barbara

  1999

• B.A.

  Princeton University

  1994

Awards & honors

• Fellow of the Materials Research Society
• Kosuke Ishii Award for Industry Education Innovation (2012)
• Global Climate and Energy Project Distinguished Lecturer (20…
• Mohr Davidow Venture Innovators Award (2007)
• Vance and Arlene Coffman Faculty Scholar Award (2007)