Novel Lower-Voltage OLEDs for High-Efficiency Lighting (Phase I)

Investigating Organization
Universal Display Corporation

Principal Investigator(s)
Dr. Brian W. D'Andrade, bdandrade@universaldisplay.com, (609) 671-0980, x 292

Subcontractor
Princeton University
University of Southern California

Funding Source
Small Business Innovation Research

Award
DOE Share: $100,000

Contract Period
7/1/03 - 4/30/04

The team led by Universal Display Corporation with their university partners at Princeton University and the University of Southern California is focusing on the development of novel, low-voltage phosphorescent light emitting structures to enable OLEDs with power efficiency >20 lm/W at a brightness of 800 cd/m². The power efficient OLEDs will result from the development of innovative, highly conductive hole and electron transport systems in conjunction with high-efficiency triplet emitters.

Triplet emitters contain a heavy metal atom that facilitates the mixing of singlet and triplet states, allowing singlet to triplet energy transfer through intersystem crossing. This leads to highly efficient devices where 100% of the excitons can potentially produce optical emission, in contrast to only approximately 25% in conventional fluorescent devices. The high conductivity hole and electron transport systems will be achieved by selecting p- and n-type dopants along with the appropriate organic buffer layers. The resulting structure will be a p-i-n type device. The team has already identified several candidate material systems and is currently working to improve their stability.

The novel structures will also have potential use in energy-efficient, long-lived, solid state white OLED applications in general illumination, automotive, and wearable electronics. The team is already exploring two approaches for generating white light in a parallel Phase 1 SBIR effort. The first approach is based on a simple striped R-G-B configuration, and the second on using a phosphorescent monomer-excimer emission layer. P-i-n doping can be incorporated into both of these approaches.

The purpose of this Phase 1 was to demonstrate and deliver to DOE a white light phosphorescent OLED (PHOLEDä) light source, employing p- and n-type conductivity dopants, having a power efficiency close to 20 lm/W at a luminance of 800 cd/m².

Specifically, the key objectives of Phase 1 were:

1. Demonstrate and deliver a white PHOLED light source on a glass substrate with a drive voltage close to 3V at 800 cd/m2 luminance through the use of conductivity doped p-type and n-type transport layers.

2. Investigate the use of ion implantation to improve the efficiency of the doping process.

3. Develop organic dopants for n-type organic transport layers.

4. Characterize the above white light sources and demonstrate > 20 lm/W at 800 nits brightness for a CIE of (0.33, 0.33) and CRI > 75.

During Phase I of the pin PHOLED program, the team met the Phase 1 goal and developed a low voltage, 20 lm/W white PHOLED as well as explored strategies to improve device stability.  These efforts led to an 6.3 V, 19.7 lm/W white device with CIE (0.39, 0.40) at 800 cd/m², a 7.0 V, 17.1 lm/W green PHOLED with a lifetime of 35 h under an accelerated constant current drive of 40 mA/cm2, and a novel n-type dopant with reduced diffusivity.

Content dated 2/08