A novel technique utilizing pressure treatment has enabled significant advancements in the field of photonics through the enhancement of white-light emission from zinc-isophthalate (Zn-IPA) metal-organic frameworks (MOFs). Researchers have successfully achieved photoluminescence quantum yield of 81.3%, which is among the highest reported for single-component MOFs, allowing for new applications in areas like lighting and display technologies.
Historically, attempts to create white-light emissions from metal-organic frameworks relied heavily on integrating multiple phosphorescent compounds or chromophores, which posed challenges linked to color stability and precise control. This study, newly published, illuminates the ability to create white light from Zn-IPA MOFs without complicate chromophoric integrations.
By applying high-pressure treatment — approximately 20.0 GPa — researchers introduced asymmetrical metal-ligand chelate coordination within the framework, fundamentally altering its electronic state. This modification significantly narrows the energy gap (ΔEST) between singlet and triplet states, effectively accelerating the intersystem crossing (ISC) process and increasing the availability of triplet excitons for radiative decay.
Initial experiments indicated only weak blue-light emission from Zn-IPA at ambient pressure. Remarkably, when pressure was increased to 10.4 GPa, the emission intensity surged sevenfold, paving the way for new emission properties. After decompression from high pressure, intense dual-emission characteristics were observed, indicating the presence of new electronic states and their contributions to white-light generation.
"This remarkably boosted the phosphorescent emission and manipulated the population of singlet and triplet excitons," noted the authors of the article, highlighting the breakthrough potential of their research. Upon complete pressure release, white-light emission was recorded across the entire visible spectrum from 350 nm to 800 nm, showcasing the distinct advantages of utilizing pressure treatment to enable functional attributes previously unachievable within single-component systems.
Further investigation revealed the practical applications of these findings, including the development of time-delay phosphor-converted light-emitting diodes (pc-LEDs), which remain luminous for up to seven seconds after being turned off. This provides substantial benefits for user comfort by decreasing abrupt lighting changes, which can lead to transient blindness.
According to the research, the newly emerged emission state contributing to white light lies around 518 nm, playing a significant role in narrowing the singlet-triplet gap. This achievement not only offers insight and methods for enhancing luminescence but also opens new avenues for exploring the performance of solely metal-organic frameworks without incorporating other emissive materials.
"The discovered ability to purposefully construct blue- and white-light emissions with long emission time through elaborate molecular designs would provide a promising platform for the exploration of single-component phosphorescent MOFs," said the researchers. The findings reflect Profound advancements toward dynamic applications across various fields, including advanced lighting solutions and embedded phosphorescent systems.
This groundbreaking research marks a significant step forward, showcasing the potential of pressure treatment techniques to modify the properties of MOFs, fostering innovation and application of materials with superior optical performance.