I-Corps: Stable and efficient organic light-emitting diodes (OLEDs) for applications in horticulture and architectural lighting

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The broader impact/commercial potential of this I-Corps project is the potential development of light sources that may improve indoor plant and crop growth for horticulture applications such as indoor vertical farming and hydroponics. Additionally, the proposed light sources could enhance architectural lighting by providing a more natural spectrum of color. Conventional inorganic semiconductor-based light-emitting diode (LED) devices usually do not have uniform spectral intensity across the visible spectrum. For example, white-light LED light sources used for lighting purposes can have a significant dip in emission intensity in the green part of the spectrum (called the “green gap”). Hence, objects illuminated by these LED lighting sources do not show true colors. Organic light-emitting diode (OLED) devices, on the other hand, can be produced with virtually any emission color with excellent intensity and efficiency in the green and red parts of the spectrum. OLEDs have an emitting layer containing an organic or organometallic material instead of conventional inorganic compound semiconductors. However, one persistent issue with OLEDs is in their blue emission component, which is less stable than red and green. Furthermore, light extraction efficiencies are ~20-50% and have substantial room for improvement. The proposed technology may address both issues by increasing the stability of blue OLED emission and by improved light extract across the visible spectrum. The proposed technology may produce stable light sources based on sustainable, low-process-energy organic semiconductors that have energy efficiencies comparable to traditional LED light sources, but with enhanced spectral qualities.This I-Corps project is based on the potential development of technology to improve the efficiency and stability of organic light-emitting diode (OLED) light sources. OLEDs have improved spectral qualities compared to more traditional inorganic light-emitting diodes (LEDs); however, their stability and efficiency are not yet optimal for commercial lighting applications. The proposed technology may address the low stability and efficiency of the blue component of light emission from OLEDs. Stable blue emission is necessary for both architectural and horticulture lighting and previous research indicates that the proposed core technology may increase the stability of blue OLEDs by a factor of up to 3.6 compared to existing blue OLEDs. Additionally, the efficiency of white OLEDs is not yet high enough for architectural and some horticulture lighting applications where 1,000 cd/m2 are required routinely. The proposed technology could improve OLED efficiency by increasing light extraction, which may help address the efficiency problem. Nanostructured plasmonic electrodes were designed that enhance the local electric fields at visible electromagnetic wavelengths and may be tuned depending upon the size and shape of the nanostructures. When the plasmon wavelength overlaps with the wavelength of the light-emitting materials in the close vicinity of nanostructures, it may provide faster and more stable light emission. The proposed nanostructured devices using plasmonic electrodes could have comparable electrical behavior to the typical planar metal electrodes but show superior photostability and light extraction efficiency.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.