Gregory Mcgraw

Direct vapor jet printing of three color segment organic light emitting devices for white light illumination

Organic-vapor jet printing (OVJP) is used to directly pattern small molecular weight electrophosphorescent white organic light-emitting devices (WOLEDs) consisting of parallel stripes of separate red, green, and blue OLEDs. The spatial patterning of the WOLEDs with peak forward viewing external quantum and luminous efficiencies of 7.1±0.3% and 7.0±0.4lm∕W, respectively, is accomplished by transporting the vapors of organic semiconductors through a nozzle to a translating sample substrate. Using multiple color segments to generate white light allows for the individual optimization of each color, is continuously color tunable, and can be used to compensate for differential aging of the constituent dopants. The theory and experimental results of WOLED printing via OVJP are discussed.

Organic vapor jet printing at micrometer resolution using microfluidic nozzle arrays

Organic vapor jet printing with a print head comprised of a microfluidic Si nozzle array is used to deposit parallel lines of an organic semiconductor thin film with a line width of 16u2002μm and edge resolution of 4u2002μm. Line width and feature size are functions of process conditions, depending strongly on nozzle-to-substrate separation distance. Experimental results are accurately characterized by a direct simulation Monte Carlo model. The model suggests that feature sizes of <1.5u2002μm are attainable by this printing process. The ability of the print head to codeposit doped films is demonstrated by growing the emissive layer of a green phosphorescent organic light emitting diode sandwiched between hole and electron transport layers deposited by vacuum thermal evaporation. This device had an external quantum efficiency of 8.8±1.3%, comparable to a similar device entirely grown by vacuum thermal evaporation.

Vapor‐Phase Microprinting of Multicolor Phosphorescent Organic Light Emitting Device Arrays

Multicolor electrophosphorescent organic light-emitting diode (OLED) pixel patterning by organic vapor jet printing (OVJP) is demonstrated, showing that this technique is capable of rapidly generating high-definition full-color displays. The resolution limits, and means to achieve them are described using a combination of simulation and experimental approaches.

Fluid dynamics and mass transport in organic vapor jet printing

Organic vapor jet printing (OVJP) is a high-resolution mask and solvent-free organic thin film deposition and patterning technique. In this work, we analyze factors that affect the material deposition rate and the dynamics of gas flow through an OVJP print head consisting of an array of micron-sized nozzles. Scaling laws governing carrier gas flow dynamics through a system of microchannels and nozzles are developed. From these laws, we predict the deposition rate and doping ratio of organic material as a function of carrier gas flow. The analysis is applied to an experimental print head, and is compared to results obtained via a more complex, direct simulation Monte Carlo model. The print head is used to grow efficient green phosphorescent organic light emitting diodes having an external quantum efficiency and luminance comparable to analogous devices grown by vacuum thermal evaporation.