RASEI

How one engineering alum optimizes clean energy operations before they break Aoife Henry (PhDElEngr‘24) is optimizing technology for wind and solar energy operations. The graduate is leading Zentus, a startup she founded that addresses a

Aoife, who worked with RASEI Fellow Lucy Pao, is leading startup Zentus, that uses machine learning to forecast and prevent equipment failures in renewable energy installations. Check it out here:
www.colorado.edu/ecee/enginee...

Excellent update on what RASEI doctoral graduate Aoife Henry (PhDEIEngr’24) is up to now.

Influence of Ligand Exchange on Single Particle Properties of Cesium Lead Bromide Quantum Dots Improving the properties of perovskite quantum dots (QDs) for quantum-light applications such as single photon emission requires a systematic understanding of the influence of ligand surface chemistry on single particle properties including line width and photoluminescence (PL) blinking. Here, we investigate the influence of ligand exchange on both the optical and structural properties of the single QDs. We examine PL blinking using a wide-field fluorescence microscope with ligand-exchanged QDs. We find that the zwitterionic ligands lecithin and phosphoethanolamine (PEA-C8C12) reduce blinking compared to dodecylammonium bromide (DDAB) and a bidentate dicationic quaternary ammonium bromide (DC) ligands, which have mono- and bidentate cationic head groups, respectively. The champion PEA-C8C12 shows a nonblinking fraction of 0.21, compared to 0.01 for the cationic-capped QDs. We further investigate the effect of ligand capping on low-temperature line width. We probe single particle line widths and show that zwitterionic PEA-C8C12 and lecithin outperform the cationic surface ligands for ligand-exchanged samples, having a narrower average single particle line width (24 meV for lecithin and 18 meV for PEA-C8C12 compared to 39 meV for DC-capped and 42 meV for DDAB-capped QDs) over long integration times. We rationalize these findings by quantifying ligand surface coverage using nuclear magnetic resonance, observing that QDs capped by zwitterions have higher ligand surface coverage (6.5 ± 1.6 for lecithin and 7.4 ± 1.9 ligands/nm2 for PEA), consistent with their superior performance at the single particle level. These line width and blinking results show that zwitterionic ligands are a preferable design strategy for reducing PL blinking and improving single particle line widths.

Quantum dots are important materials for efficient displays, high-speed communications and low energy electronics. This collaboration details how we can tune the properties of the quantum dots by molecularly engineering the ligand structure around the quantum dots: doi.org/10.1021/acs....

Origins of anisotropic linear magnetoresistance with isotropic mobility in Cd3As2 films on GaAs[110] Thin film synthesis allows for the potential to orient crystals in different orientations, permitting measurement of orientation-dependent material aspects such

Molecular-level engineering of materials offers the development of novel properties that can be exploited in new technologies. This report describes a new tool, through controlled growth of films that can influence the orientation and size of crystals in the material: doi.org/10.1063/5.03...

222 nm UV Pretreatment to Mitigate Organic Fouling of Reverse Osmosis Membranes in Wastewater Reuse Reverse osmosis (RO) membranes used for wastewater reuse are vulnerable to organic fouling, necessitating effective pretreatment for a sustainable operation. Here, we evaluate the potential of 222 nm UV irradiation as a chemical-free pretreatment to transform organic matter from secondary wastewater effluent prior to RO. 222 nm UV generally achieved greater fouling control than conventional 254 nm UV with hydrogen peroxide, reducing flux decline from wastewater effluent fouling by 60% (fluence of 400 mJ/cm2) versus 29% for 254 nm + H2O2 (fluence of 1000 mJ/cm2), relative to untreated wastewater. Size-exclusion chromatography revealed that both UV wavelengths decreased high molecular weight (MW) organics, but only 222 nm UV substantially degraded medium-low MW TOC fractions, which correlated with fouling reduction. In contrast, we observed significant protein conformational changes induced by 222 nm UV could increase fouling for certain feed waters and treatment conditions. Characterization of the fouled membrane surface showed that 222 nm UV-treated water formed a more porous fouling layer with more oxidized carbon than did untreated and 254 nm UV-treated waters. Overall, this work found 222 nm UV to be a promising, chemical-free pretreatment to RO and underscores the importance of water-specific process optimization.

Reverse osmosis filters, effective for wastewater purification, are vulnerable to organic fouling and often require pretreatment. This collaborative work explores using UV light as a pretreatment method, replacing chemical additives to improve filtration performance: doi.org/10.1021/acse...

Electrochemical quantification of phosphonic acid passivated surface sites of NiOx for perovskite solar cells Nickel oxide (NiOx) is among the few p-type metal oxide semiconductors considered a strong candidate for hole transport layers in halide perovskite solar cells (PSCs). However, its reactivity with per...

When solar cell forms a charge, a crucial component transports it to the grid. This work explores nickel oxide, a promising charge transport layer for perovskite solar cells, but it can cause perovskite decomposition. New additives prevent this breakdown: doi.org/10.1039/D5EE...

Nickel-oxide hole-transport layers prevent abrupt reverse-bias breakdown and permanent shorting of perovskite solar cells caused by pinhole defects When perovskite solar cells (PSCs) are subjected to reverse bias, they often abruptly pass large current densities through localized film defects. The large, localized current induces heating that qui...

When perovskite solar cells try to operate in the shade, it can cause electrical shorting that can cause permanent damage. This study introduces a new layer that prevents this damage and provides a more stable solar cell: doi.org/10.1039/D5EL...

Mechanism-Informed Breakdown: Understanding Degradation by Controlling Voltage-Hold Patterns in Proton Exchange Membrane Water Electrolyzers Low catalyst loadings pose challenges to performance stability in proton exchange membrane (PEM) water electrolysis over extended operation. To study the impact of degradation mechanisms and voltage loss rates, different stress tests are applied to membrane electrode assemblies. Potential cycling conditions were observed to induce higher degrees of iridium (Ir) oxide crystallization, ionomer degradation, and catalyst layer (CL) thinning, which likely contributed to higher kinetic loss rates. On the other hand, while Ir migrating into the PEM (Ir band) generally impairs performance, the interconnected and more uniform Ir band formed under a constant 2 V hold may allow for Ir at the catalyst/membrane interface to remain electronically connected and kinetically accessible, as well as indicate greater Ir site access during the applied stressor. The 2 V hold also demonstrates improved kinetic durability through a lower Tafel slope, faster polarization kinetics, and reduced charge transfer resistance. In contrast, potential cycling caused the migration of disconnected Ir agglomerates into the membrane bulk and created a steady increase in charge transfer resistance, a more dramatic decrease in capacitance (46.7% loss), and significant damage to the surrounding ionomer, indicating a decline in both the quality and quantity of active sites in the anode CL. This work underscores the distinct degradation pathways associated with load holds versus cycling, highlighting the role of catalyst–ionomer interactions in kinetic performance and long-term stability. These insights can inform operational strategies for PEM electrolyzers powered by intermittent energy sources, aiming to minimize efficiency losses over extended operation.

Special plastics can be used to accelerate the splitting of water into hydrogen, a potential clean fuel, using electricity. They are prone to fall apart. This study uses advanced microscopic techniques to understand how they decompose, providing insights for future designs: doi.org/10.1021/acsa...

Impact of Cation Insertion on Semiconducting Polymer Thin Films toward Electrochemical Energy Conversion Semiconducting polymers are being explored for electrochemical and photoelectrochemical energy transformation and storage applications. For these applications, it is critical to understand how ion insertion from the electrolyte into polymer electrodes modulates the polymer electronic structure and electron doping levels. This study explores electrochemical cation insertion in the n-type conjugated redox polymer P90, composed of alternating naphthalene diimide (NDI) acceptor and bithiophene (T2) donor units, where the NDI units are functionalized with heptaethylene glycol (HEG, 90%) and 2-octyl dodecyl (OD, 10%) side chains. By combining in situ techniques (UV–vis absorption and Raman spectroscopies with electrochemistry), structural analysis using ex situ grazing-incidence wide-angle X-ray scattering (GIWAXS), and density functional theory (DFT) calculations, we reveal that dications enable negative polaron and bipolaron formation in the P90 at less reducing potentials while supporting more bipolaron formation than the monocations; moreover, larger dications with smaller hydrated radii increase the maximum P90 electron doping level. We also determine that the monocations lead to more thermodynamically stabilized polarons compared with the dications. These findings highlight the critical role of cation identity in tuning electrochemical charging, charge stabilization, and electronic structure of n-type conjugated redox polymers, providing guidance on the rational design of polymer-based (photo)electrochemical applications.

Organic semiconductors promise electronics that can be tuned, are flexible, and robust. This report describes how charged atoms can be injected into the polymer to tailor their electronic properties for use in solar panels, electronics, batteries and electrocatalysts: doi.org/10.1021/acs....

Polariton Control of Molecular Charge Transfer in Perylene Diimide Semiconductors We report the modulation of molecular charge transfer in a bay-substituted perylene diimide derivative embedded in a planar distributed Bragg reflector microcavity. Angle-resolved reflectance spectra ...

Being able to control electronic charge is fundamental to how electronic and communications devices work. Being able to control this using light offers fast and energy efficient control, this collaboration describes a new organic semiconductor that can offer such control: doi.org/10.1021/acs....

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

Researchers have been exploring how you can layer different materials to capture more light in solar panels, like a sandwich where every layer can harvest energy. Each layer has to have specific electronic properties built into it, which is what this collaboration explores: doi.org/10.1021/acs....

Limiting phosphonic acid interlayer–perovskite reactivity to stabilize perovskite solar modules Phosphonic acid (PA)–based interlayers used in metal-halide perovskite solar cells (PSCs) can suffer from instability at elevated temperatures. We report that the acidic protons of PAs weakly bound to...

Out on day 1 of 2026, this collaboration published in Science describes how perovskite solar modules can be made more stable and efficient. By designing a stronger molecular layer of phosphonic acids, these solar cells keep working longer and lose less power over time. doi.org/10.1126/scie...

RASEI January 2026 Research Roundup💡🧪

The RASEI community started out fast in 2026, with 10 papers published in January 🚀. These cover a wide range of topics from how we can make wastewater purification more efficient to how electrons move in one-molecule thick films!

Announcing the 2026 Three Minute Thesis Winners Eleven students participated in this year’s final competition for a chance at prize money and a chance to represent CU Boulder at the regional competition.

Congratulations to all the presenters, Check out a 3MT near you! The recording will be online soon! www.colorado.edu/graduatescho...

RASEI Graduate student Ben Hammel, a member of the Dukovic Group, participated in the CU Boulder 2026 3MT competition last week. Ben was one of 11 graduate students who presented, which made for an evening of exciting and interesting stories.

The Three Minute Thesis (3MT) is an academic competition that challenges graduate students to hone their presentation skills and present the premise and results of their entire thesis in just three minutes.
www.colorado.edu/graduatescho...

In addition to the four RASEI Fellows, this work includes the Ginger Group at the University of Washington, and was part of the U.S. National Science Foundation STC, IMOD. imod-stc.org

This research shows that through careful design of the ligand structure, the properties of the whole quantum dot can be changed, important in their application in different devices and technologies.

Influence of Ligand Exchange on Single Particle Properties of Cesium Lead Bromide Quantum Dots CHEMISTRY OF MATERIALS, 2026, ASAP

Quantum Dots, the materials found in QLED displays, and at the forefront of light driven communication, require a layer of what we call ligands – these are essentially a protective layer from their surroundings. www.colorado.edu/rasei/2026/0...

Just out in Chemistry of Materials, this highly collaborative article, that includes four RASEI Fellows, describes how you can tune the properties of quantum dots, important materials for displays, communications, and new, more energy efficient, electronic technologies.

Locking in Solar Power: How a Stronger Interlayer Boosts Perovskite Cell Durability JANUARY 2026

Find out more about how the team proposes that better understanding the details around these buried interfaces is key to improving these devices in the highlight here:
www.colorado.edu/rasei/2026/0...

Solar cells using this new molecule set new benchmarks, able to run under continuous bright light for nearly 3,000 hours, only losing 10% of their efficiency, a level of durability not previously seen for this class of solar cell.

This layer is just one molecule thick, and made up of a class of molecules called phosphonic acids. This collaboration designed and tested a series of different phosphonic acids and identified ones that could carry charge, and stuck tightly to the other layers.

This dropped the efficiency of the solar cell and led to significant reductions in the operational lifetime of the solar devices.

Solar cells are made up from a series of layers, all of which have specific designed roles in converting light to electricity. It was found that one of these was not bonding strongly enough, and when it came loose, was actually poisoning the other layers.

Limiting phosphonic acid interlayer–perovskite reactivity to stabilize perovskite solar modules Phosphonic acid (PA)–based interlayers used in metal-halide perovskite solar cells (PSCs) can suffer from instability at elevated temperatures. We report that the acidic protons of PAs weakly bound to...

Out last week in Science, a collaboration involving RASEI Director Seth Marder, that uses a molecular engineering approach to develop more robust and efficient solar cells.
doi.org/10.1126/scie...

The Filament Factory: How two specialized cells team up to build microscopic rock and drive carbon capture January 2026

Check out our highlight of the work here: www.colorado.edu/rasei/2026/0...

In addition to the great scientific value of these studies, the videos captured are quite amazing, providing an exciting window into the precise workings of this microscopic world.

It was thought that formation of these minerals was a slow, uniform chemical reaction influenced by the environment, the ability to see in real time reveals controlled mechanisms that are dictated by cell-specific functions. This suggests we could control these processes for new applications.

This process is already a fundamental step for large-scale applications, such as oceanic buffering, soil improvement, and living building materials that can capture and sequester carbon from the air.