Phosphorescent

Samsung Display's Lee Chang-hee, VP and head of SDC's research center, gave a talk during K-Display 2024, and updated that Samsung is progressing towards a next-generation blue OLED emitter technology in two tracks.

SDC is working with Universal Display, to adopt the company's blue PHOLED system. This is progressing, but SDC says that the pace is slow - indeed we heard from UDC lately that the introduction of a commercial material will take longer than expected.

OLED displays have been gaining popularity rapidly, and are already the dominant smartphone display technology. OLEDs are also the display technology of choice in the smartwatch market, making inroads into the TV, monitor, laptop and tablet markets. The future of the OLED industry looks bright.

In recent years, the focus of the industry, beyond increasing capacity and reducing production costs, has been improving the performance of OLEDs in the areas of display brightness, efficiency, and lifetime. Brightness is required in many applications - from TVs (for HDR and to view in ambient lighting) through smartphones (outdoor viewing) to automotive, and efficiency is a plus in any scenario (but mostly in mobile displays). Display lifetime is already good enough for many applications, but in some cases (like automotive, and IT displays) it is critical. These three properties usually go together - if you can make more efficient OLED displays, you can drive them at a lower current to achieve the same brightness, and so lifetime increases, or you can achieve higher brightness, etc. 

Researchers from Osaka University have found that thienyl diketone, a new organic molecule, shows high-efficiency phosphorescence, and one that is more than ten times faster than traditional organic phosphorescence materials. Such a material could hold promise for highly-efficient phosphorescence emission without the use of heavy metals. 

The researchers explain that phosphorescence occurs when a molecule transitions from a high-energy state to a low-energy state, and it often competes with non-radiative processes (i.e. heat generation instead of light). This competition with the non-radiative process leads to slow phosphorescence and lower efficiency. This is solved by adding heavy metal into the emitter - but this new breakthrough achieves fast emission without the heavy metal.

Universal Display Corporation reported its financial results for Q4 2023, with revenues of $158 million, and a net income of $62 million. For the whole year (2023), UDC reproted revenues of $576 million and net income of $203 million. The company ended 2023 with $800 million in cash and equivalents, and has increased its quarterly dividend.

UDC says that the market still suffers from soft spending in smartphone and premium TVs. UDC, however, says that it believes that the OLED industry is starting a new and exciting multiyear investment cycle.

Researchers from the University of Michigan developed a new OLED emitter system, based on a blue phosphorescence emitter, based on the polariton-enhanced Purcell effect. This new emitter systems offers high stability and high efficiency. 

The basic idea is to start with a light-blue (cyan) phosphorescence emitter (which offers a longer lifetime than a deep blue emitter), and placing it between two mirrors. The distance between the mirrors is controlled so that only deep blue light waves persist and are emitter from the mirror chamber. The researchers also tuned the optical properties of the OLED stack to the adjacent metal electrode which introduced a new quantum mechanical state called a plasmon-exciton-polariton, or PEP. This new state allows the organic material to emit light very fast, thus even further increasing the lifetime by decreasing the opportunity for excited states to collide and destroy the light-emitting material.

Researchers from Korea's Dongguk University developed a new green phosphorescent OLED emitter based on a manganese complex called MnBz. The green MnBz emitter offers high brightness and efficiency and low-cost fabrication without any heavy metals. The green emitter was also used to create a warm-white OLED device.

The new emitter is based on a a zero-dimensional manganese (Mn)-based complexes, produced via solution processing. The green phosphorescent OLED offers a record-breaking quantum efficiency of 11.42% and current efficiency of 56.84 cd A^-1.