Two Additives, One Timing Trick: Deep-Red Perovskite LEDs Hit Record Efficiency and Stability

Deep-red light sits at a curious sweet spot in modern optoelectronics. It penetrates biological tissue more gently than shorter wavelengths, it is essential for next-generation displays, and it underpins infrared-adjacent technologies from night-vision aids to optical communications. Yet for one of the most promising emissive materials on the planet, the metal-halide perovskite, reaching efficiently into the deep-red has proven stubbornly difficult. A new study published in the Journal of Materials Science by Yi Shao and Jie Yang, researchers affiliated with the University of Science and Technology of China and the Chinese Academy of Sciences, reports a deceptively simple fix: instead of dumping additives into the perovskite precursor all at once, the team delivers two different molecules at two different moments during film formation. The result is a deep-red light-emitting diode that glows at 734 nanometers with an external quantum efficiency of 21.70 percent and an operational lifetime that stands out for this notoriously fragile class of devices.

To appreciate why the timing of additive delivery matters, it helps to understand what makes mixed-halide perovskites both brilliant and brittle. Perovskites are crystalline materials built from a framework of lead and halide ions, typically iodide and bromide in red-emitting compositions, interspersed with organic or inorganic cations. By blending halides, engineers can tune the bandgap and therefore the emission color with remarkable precision. But that same blend is the source of the material’s Achilles heel. Under the electric field inside a working LED, halide ions migrate through the crystal lattice, segregating into iodide-rich and bromide-rich domains. The emission color drifts during operation, a phenomenon that has plagued spectrally stable mixed-halide devices for years. At the same time, defects, uncoordinated lead atoms, missing halides, and disordered grain boundaries, act as traps where injected electrons and holes recombine without emitting a single photon, draining efficiency.

The conventional response has been additive engineering: sprinkle passivating molecules into the precursor solution and hope they find their targets. The problem, as the new work makes clear, is that a perovskite film does not form all at once. It crystallizes in stages, from nucleation through grain growth to final film consolidation, and an additive introduced into the precursor is present from the very beginning whether it is needed there or not. A molecule that is ideal for patching grain boundaries late in the process may instead interfere with early nucleation if it is present from the start. Shao and Yang’s insight was to treat film formation as a choreography rather than a single event, matching each additive to the stage where it can do the most good.

The first additive, 4-vinylbenzylammonium iodide, or VBAI, goes into the precursor solution itself. As an ammonium salt, it belongs to a family of molecules well known in the perovskite community for defect passivation. The ammonium group can hydrogen-bond with the perovskite framework, while the iodide counterion helps replenish halide vacancies, one of the most damaging defect types in these materials. The vinylbenzyl portion adds a bulky aromatic character that can help anchor the molecule at the perovskite surface and, in principle, stiffen the lattice against ion migration. By placing VBAI in the precursor, the researchers ensure it is incorporated during crystallization, where it can influence grain growth and passivate defects as they form rather than after the fact.

The second additive, octylphosphonic acid, or OPA, takes a different route entirely: it is dissolved into the antisolvent, the liquid dripped onto the spinning precursor film to trigger rapid crystallization. Phosphonic acids carry a distinctive dual personality. The phosphonic acid head is a strong Lewis base that coordinates to undercoordinated lead atoms at the perovskite surface, neutralizing deep traps that would otherwise swallow charge carriers. The long octyl chain, meanwhile, is hydrophobic and insulating, and previous work has shown that octylphosphonate species can self-assemble into robust hydrogen-bonded networks that wrap around perovskite grains, shielding them from moisture and thermal stress. Delivering OPA through the antisolvent means it arrives precisely at the moment the film is solidifying, positioning it at surfaces and grain boundaries where its protective chemistry is most valuable, without contaminating the early nucleation chemistry.

The complementary division of labor between the two additives is the conceptual heart of the paper. VBAI, present from the start, shapes the crystal growth itself; OPA, arriving with the antisolvent, seals and protects the finished grains. Combined experimental characterization and density functional theory calculations, performed with the widely used plane-wave codes developed by Kresse and Furthmüller, support this picture. The dual-additive films show improved morphology and crystallinity, meaning larger, better-ordered grains with fewer boundaries where ions could hop and traps could lurk. The measured trap density drops, and with it the rate of non-radiative recombination, the silent efficiency killer in every LED. The films also hold up better against heat and resist the spectral drift that normally afflicts mixed-halide emitters under sustained operation.

The device numbers translate the materials science into something display engineers and optoelectronics researchers can actually use. The optimized deep-red PeLEDs emit at an electroluminescence peak of 734 nanometers, squarely in the deep-red region where perovskite performance has historically lagged behind green and red-emitting cadmium-based and organic alternatives. The maximum external quantum efficiency of 21.70 percent means that more than one in five electrons injected into the device emerges as a useful photon, a figure that places these diodes among the more efficient deep-red perovskite emitters reported to date. Just as important for any practical application, the operational lifetime, quantified as T50, the time for brightness to fall to half its initial value, reaches 26.39 hours. For a device class where spectral instability and rapid degradation have often limited lifetimes to minutes or a few hours, that is a meaningful step forward, even if it remains far from the tens of thousands of hours demanded of commercial display panels.

The strategy also fits into a broader and rapidly maturing research landscape. The paper’s reference list reads like a map of the field’s recent trajectory: Nature Photonics work on interfacial reactions for bright and stable deep-red devices, Advanced Materials reports on space-confined fabrication of cesium lead iodide nanocrystal films and lateral zero-dimensional/three-dimensional heterostructures, and a growing literature on dual-additive and dual-site strategies borrowed from perovskite solar cell research. Ammonium salts have been shown in multiple studies to passivate different defect types selectively, and phosphonic acid modifiers have already proven their worth in blue perovskite LEDs and high-efficiency solar cells. What Shao and Yang add to this conversation is the stage-dependent logic, the recognition that where and when an additive enters the process can matter as much as which molecule you choose. That principle is transferable: the same reasoning could guide additive selection for blue and green perovskite emitters, for wide-bandgap compositions in tandem solar cells, and for any application where crystallization kinetics and defect chemistry must be tamed simultaneously.

Caveats remain, as they always do on the road from laboratory record to living-room screen. The T50 lifetime of roughly 26 hours was measured under the specific operating conditions of the study, and translating such results to the higher brightness and harsher duty cycles of commercial displays will require further gains in encapsulation, thermal management, and ion-migration suppression. Lead toxicity continues to shadow the entire perovskite field, motivating parallel work on lead-free compositions and on recycling strategies. Still, the study demonstrates that some of the perovskite LED’s most stubborn problems, defect-assisted recombination, halide segregation, and thermal degradation, can be attacked with nothing more exotic than two well-chosen small molecules added at the right moments in a standard solution-processing workflow. No new deposition equipment, no high-temperature steps, no rare-earth chemistry. If the stage-dependent additive philosophy proves as general as the authors suggest, the humble antisolvent drip may turn out to be one of the most powerful levers in perovskite engineering, and deep-red perovskite LEDs may finally be on a credible path from the optics bench to the display stack.

Subject of Research: Stage-dependent dual-additive engineering of mixed-halide perovskite films for efficient and stable deep-red light-emitting diodes

Article Title: Efficient and stable deep-red mixed-halide perovskite LEDs via dual-additive engineering

Article References: Shao, Y., & Yang, J. (2026). Efficient and stable deep-red mixed-halide perovskite LEDs via dual-additive engineering. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13948-6

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13948-6

Keywords: perovskite LEDs, deep-red emission, mixed-halide perovskites, additive engineering, defect passivation, ion migration, VBAI, octylphosphonic acid, external quantum efficiency, spectral stability, crystallization kinetics, optoelectronics