The breakthrough, published in the journal Advanced Optical Materials, centres on a molecule capable of measuring both air pressure and temperature at the same time, from the same spot on a surface. Most sensors can only measure one property at a time, like a thermometer for temperature or a pressure gauge for pressure. Measuring two properties accurately from the same surface at the same moment usually means deploying two separate instruments, which adds cost and complexity to an already intricate testing process. The new molecule sidesteps that requirement entirely by emitting two distinct colours of light simultaneously: one signal that responds to both air pressure and temperature, and another that responds only to temperature. By comparing the two, the molecule itself provides a corrected pressure reading without any external temperature sensor.

Dr Alexander Romanov, Senior Research Fellow in the Department of Chemistry at The University of Manchester, explained the dual nature of the emission. The Manchester material emits red light, a form of phosphorescence, which is sensitive to changes in both pressure and temperature. At the very same time, it emits blue light as fluorescence, responding only to temperature. By measuring blue and red light at once, researchers obtain everything needed to separate the pressure signal from the temperature interference. According to Romanov, that kind of built-in self-correction is simply not possible with a standard light-emitting molecule, which is precisely why the achievement matters for the aerospace industry.

The chemistry behind the molecule is as elegant as the concept. The structure is built around a gold atom bonded to a ring-shaped compound called acridine, and remarkably, the position of that bond within the molecule determines which type of light it produces. Gold was chosen because even subtle changes to where it sits within the structure produce reliably different light-emitting behaviours, giving chemists precise control over the sensing properties. When the gold atom bonds to one position on the molecule, it triggers the pressure-sensitive red emission; a bond at a different position triggers the temperature-only blue emission. This positional sensitivity turns a single molecular scaffold into a two-channel sensor, with each channel carrying distinct physical information about its environment.

Theoretical work played a crucial role before any molecule was made. Calculations carried out by collaborators at the University of Eastern Finland helped the Manchester team understand and predict the differences in emission behaviour before the compound was built in the laboratory. That predictive step is significant because designing dual-emitting molecules is notoriously difficult: the two emission pathways must coexist in the same structure without quenching each other, and their responses to external conditions must be cleanly separable. With the computational groundwork in place, the team could proceed to synthesis with a clear target, confident that the gold-acridine framework would deliver the two independent optical signals the concept required.

In practical use, the molecule is embedded in a paint applied to test models in the standard way for pressure-sensitive paint measurements. A camera captures both emission colours at the same time, and the ratio between the two signals automatically corrects for temperature, without any separate temperature sensor being mounted on or near the model. This ratio-based approach is the key to the self-correction. Because temperature affects both emissions while pressure affects only one, the blue signal acts as a continuous internal reference. Dividing one signal by the other cancels out the thermal contribution mathematically, leaving a clean pressure measurement even as the surface temperature of the model drifts during a run.

The implications for wind tunnel testing are considerable. Dr Mark Quinn, Reader in the Department of Mechanical and Aerospace Engineering at The University of Manchester, noted that temperature correction is currently one of the main challenges to making pressure-sensitive paints reliable. Having both pressure and temperature measurements come from the same molecule simultaneously is, in his view, a more elegant solution, and potentially a more practical one for real test conditions, where adding extra instruments creates its own complications. Traditional temperature correction often relies on infrared cameras, embedded thermocouples, or separate temperature-sensitive paints, each of which adds expense, calibration burden, and potential sources of error to a test campaign.

Pressure-sensitive paint technology itself deserves a closer look, because it represents a fundamental shift in how aerodynamicists gather data. Before such paints existed, mapping surface pressure required drilling hundreds of tiny pressure taps into a model and connecting each one to a transducer, a slow and expensive process that provided data only at discrete points. Pressure-sensitive paint turns the entire surface into a continuous sensor: illuminate the coating, photograph its glow, and the brightness map becomes a pressure map across the whole model. The catch has always been that the luminous molecules in these paints are also thermally active, so a wing that warms under the tunnel lights or cools in the airflow produces glow variations that masquerade as pressure changes. The new dual-emitting molecule attacks that vulnerability directly within the paint itself.

The work sits within a broader programme of research at Manchester into improving pressure-sensitive paint for aerospace applications. A related study, recently published in ACS Applied Engineering Materials, addresses the temperature problem from a different direction, by designing a platinum-based paint with inherently low temperature sensitivity. Together, the two studies represent complementary approaches to one of the industry’s most persistent challenges. One strategy minimises the temperature response at the level of the emitting molecule; the other, embodied in the new gold-acridine complex, accepts the temperature response but measures it simultaneously so it can be subtracted. Having both tools available gives engineers flexibility to choose the approach best suited to a given test, or potentially to combine them for even greater robustness.

The research, published under the full title Temperature Correction in a Single Luminophore Pressure-Sensitive Paint Using a Dual-Emitting Gold Acridine Complex, points toward a future in which wind tunnel data is cleaner, faster to process, and less dependent on elaborate correction procedures. For an industry in which a single wind tunnel campaign can cost millions and every improvement in measurement fidelity translates directly into better aircraft, a molecule that carries its own thermometer is more than a laboratory curiosity. It is a candidate to become a standard ingredient in the paints that coat the next generation of wings, fuselages, and rotor blades, turning two colours of light into a single, trustworthy picture of the forces that keep aircraft aloft.

Subject of Research: A dual-emitting gold-acridine molecule for temperature-corrected pressure-sensitive paint in wind tunnel testing

Article Title: Two-color glowing molecule could make wind tunnel tests more accurate[

Article References: Two-color glowing molecule could make wind tunnel tests more accurate[. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: pressure-sensitive paint, wind tunnel testing, aerospace engineering, gold acridine complex, phosphorescence, fluorescence, temperature correction, molecular sensors, University of Manchester, Advanced Optical Materials, luminophore, aircraft testing

Top-emitting OLEDs are the workhorses of high-resolution active-matrix displays because their light exits away from the substrate, decoupling the emitting aperture from the transistor backplane beneath. They also lend themselves naturally to a Fabry–Perot microcavity, formed between a reflective bottom electrode and a semitransparent top cathode. The cavity narrows the electroluminescence spectrum and concentrates emission toward the forward direction, boosting frontal efficiency and color purity. But the same physics that sharpens the spectrum also makes extraction design unforgiving: much of the generated light ends up confined in waveguide modes traveling laterally through the organic stack and in surface plasmon polaritons hugging the metal electrodes. Fixing the air-side interface alone cannot recover those internal losses.

Conventional internal outcoupling structures, such as wrinkles, corrugations, and strongly curved microlens textures, scatter trapped modes back toward useful directions, but they carry a hidden cost. When the underlying texture is steep, the organic layers deposited on top fail to follow it conformally, so the local optical thickness of the cavity varies across the device and the resonance condition drifts from point to point. Stronger scattering then does not translate into a better device, because the cavity-defined forward emission benefit is simultaneously eroded. The key insight of the new work is that the geometry of an internal extraction layer must be judged not just by how much light it scatters but by how gently it does so.

The researchers call their solution a gentle internal corrugation layer, or GICL. Atomic force microscopy over a 50 by 50 micrometer area revealed a peak-to-valley height of about 1.12 micrometers with root-mean-square roughness of 144.5 nanometers, but the defining feature is the slope: representative surface angles of only 2.1 to 6.9 degrees along one axis and 1.8 to 3.5 degrees along the other, spread over lateral spans of nearly 9 micrometers. Cross-sectional electron microscopy showed the entire multilayer stack following this soft undulation without discontinuities. The contrast with reference structures is instructive. A steep imprinted random microlens array reached surface angles of 25.3 degrees with a peak-to-valley height of 7.87 micrometers, while one wrinkle reference achieved low roughness yet still exhibited angles above 53 degrees, demonstrating that roughness amplitude alone says little about geometric severity.

Finite-difference time-domain simulations confirmed that gentler is genuinely better. Among the compared structures, GICL yielded the highest relative total simulated power, outperforming both wrinkle references and the steep microlens array, even though the latter produced far stronger local field perturbation. Ray tracing sharpened the picture: GICL directed 77.3 percent of input power into the forward collection region, versus 43.5 percent for the microlens array, which instead diverted light into wide-angle, internally reflected, and backward trajectories. Under identical conditions, the calculated light extraction efficiency rose from 37.6 percent for the planar microcavity device to 74.1 percent with GICL, an increase of nearly a factor of two. An intermediate-index clear resin with a refractive index of 1.59 was applied at the outer surface to soften the air interface and let the redistributed light actually escape.

The emissive system matters as much as the geometry. In a microcavity, only the spectral portion of the emitter that overlaps the resonance band contributes efficiently to the enhanced external output, so a broad emitter wastes much of its spectrum on off-resonant wavelengths. The team used a phosphor-assisted thermally activated delayed fluorescence sensitization scheme, in which a TADF host and a phosphorescent assistant funnel excitation energy to a terminal multi-resonance TADF emitter called tCzphB-Fl, producing green emission with a full width at half maximum of only about 19 to 22 nanometers. When the microcavity was formed, the narrowband system’s peak shifted just 2 nanometers and its FWHM narrowed from 22 to 19 nanometers, whereas a conventional phosphorescent comparator shifted 13 nanometers and narrowed from 65 to 25 nanometers, evidence that most of the narrowband emission already sat inside the resonance band.

Device results bore out the combined strategy. All GICL devices shared the same 2.25-volt turn-on voltage and essentially unchanged current density, ruling out electrical effects, and the forward spectra showed only minor changes, ruling out spectral reshaping. Under matched resin conditions, adding GICL raised the external quantum efficiency from 34.8 to 69.2 percent, current efficiency from 302.7 to 378.4 candela per ampere, and power efficiency from 199.3 to 396.7 lumens per watt, with maximum luminance reaching nearly 120,000 candela per square meter. Across five samples the efficiencies averaged 68.2 plus or minus 0.7 percent, indicating good reproducibility. The angular color shift at 60 degrees off-axis also fell from 0.0197 to 0.0086 in CIE 1976 coordinates, and the luminance distribution became more Lambertian, both valuable for display uniformity.

Polarization-resolved measurements identified where the recovered light had been hiding. Because waveguide modes are predominantly transverse-electric like and surface plasmon polaritons are transverse-magnetic like, separating the s- and p-polarized emission provides a mode-sensitive diagnostic. Both polarized components, and the non-polarized total, increased across the viewing-angle range in the corrugated device, confirming genuine extraction rather than mere redistribution between channels. Quantitative modal analysis showed the outcoupled fraction rising from 29.7 to 38.6 percent, with the waveguide fraction dropping from 40.0 to 32.0 percent and the plasmon-related fraction changing only modestly. The roughly 30 percent simulated gain in outcoupled power matched the approximately 25 percent uncorrected device-level increase closely, lending quantitative coherence to the extraction interpretation.

Notably, the same corrugation helped the broad phosphorescent system far less, lifting its current efficiency by only about 15.7 percent compared with 25.0 percent for the narrowband system, a difference the authors attribute to spectral overlap with the cavity resonance rather than to bandwidth alone, since the two emissive chemistries differ in other respects as well. The gains did come with a small price: efficiency roll-off at high brightness was moderately larger in the corrugated devices, possibly reflecting local current crowding on the textured surface, and operational lifetime at 1,000 candela per square meter was slightly shorter, though still comparable at about 101 hours to 95 percent of initial luminance. The broader lesson stands: in microcavity OLEDs, internal texture geometry, outer-interface index matching, and emitter-resonance alignment must be engineered together, and gentleness, it turns out, extracts more light than force.

Subject of Research: Cavity-compatible internal light extraction in top-emitting microcavity OLEDs using a gentle corrugation layer and resonance-matched narrowband emission

Article Title: Cavity‐Compatible Light Extraction in Top‐Emitting Microcavity OLEDs via a Gentle Internal Corrugation Layer and Resonance‐Matched Narrowband Emission

Article References: Kim, Y. R., Nimbalkar, A., & Suh, M. C. (2026). Cavity‐Compatible Light Extraction in Top‐Emitting Microcavity OLEDs via a Gentle Internal Corrugation Layer and Resonance‐Matched Narrowband Emission. Advanced Science, Article e78013. https://doi.org/10.1002/advs.78013

Image Credits: AI Generated

DOI: 10.1002/advs.78013

Keywords: OLED, microcavity, light extraction, external quantum efficiency, corrugation, TADF, narrowband emission, waveguide modes, surface plasmon polariton, display technology, FDTD simulation, phosphorescence