In this Progress Report we provide an update on recent developments in inkjet printing technology and its applications, which include organic thin-film transistors, light-emitting diodes, solar cells, conductive structures, memory devices, sensors, and biological/pharmaceutical tasks. Various classes of materials and device types are in turn examined and an opinion is offered about the nature of the progress that has been achieved.

Harvesting energy directly from sunlight using photovoltaic technology is a way to address growing global energy needs with a renewable resource while minimizing detrimental effects on the environment by reducing atmospheric emissions. This issue of MRS Bulletin on "Organic-Based Photovoltaics" looks at a new generation of solar cells that have the potential to be produced inexpensively. Recent advances in solar power conversion efficiencies have propelled organic-based photovoltaics out of the realm of strictly fundamental research at the university level and into the industrial laboratory setting. Fabricated from organic materials-polymers and molecules-these devices are potentially easier to manufacture than current technologies based on silicon or other materials. In this introductory article, we describe the motivation for pursuing research in this field and provide an overview of the various technical approaches that have been developed to date. We conclude by discussing the challenges that need to be overcome in order for organic photovoltaics to realize their potential as an economically viable path to harvesting energy from sunlight.

Efficient excimer emission is demonstrated in white organic light‐emitting diodes (see figure) based on platinum(II)[2‐(4′,6′‐difluorophenyl)pyridinato‐N, C2′)](2,4‐pentanedionato) utilized in devices incorporating the novel host material 2,6‐Bis(N‐carbazolyl)pyridine (26mCPy). External quantum (power) efficiencies of 15.9 % (12.6 lm W–1) are realized at 500 cd m–2.

We demonstrate the use of screen printing in the fabrication of ultrasmooth organic-based solar cells. Organic films on the order of several tens of nanometers in thickness and 2.6 nm surface roughness were made. The first-generation screen-printed plastic solar cells demonstrated 4.3% in power conversion efficiency when using an aluminum electrode and 488 nm illumination.

Screen printing as a new approach to fabricating and patterning OLEDs is reported here. The method allows the deposition of organic layers with less than 100 nm film thickness, and is reported to be versatile, simple, fast, and cost‐effective, making it valuable for producing low information content displays. The Figure shows a photoluminescent image of a conducting‐polymer logo printed using this technique.

Surface plasmon polariton enhanced electroluminescence and electron emission from electroformed Al-Al2O3-Ag diodes J. Appl. Phys. 112, 073717 (2012) Increased efficiency of light-emitting diodes incorporating anodes functionalized with fluorinated azobenzene monolayers and a green-emitting polyfluorene derivative APL: Org. Electron. Photonics 5, 230 (2012) Increased efficiency of light-emitting diodes incorporating anodes functionalized with fluorinated azobenzene monolayers and a green-emitting polyfluorene derivative Appl. Phys. Lett. 101, 153306 (2012) An earth-isolated optically coupled wideband high voltage probe powered by ambient light Rev. Sci. Instrum. 83, 104703 (2012) Organic light-emitting diodes with direct contact-printed red, green, blue, and white light-emitting layers APL: Org. Electron. Photonics 5, 228 (2012) Additional information on Appl. Phys. Lett.

We demonstrate the fabrication of diodes having inkjet printed light emitting quantum dots layer. Close packing of printed layer is shown to be influenced by surface morphology of the underlying polymer layer and size variance of quantum dots used. We extend our approach to printing quantum dots onto a quarter video graphics array substrate (76 800 monochrome pixels). The purity of emitted electroluminescent spectra of resulting devices is related to coverage integrity of printed layer, which in turn is shown to be affected by the number of printed drops per pixel.

We report a two-layer, blue organic light-emitting diode with a 4,4′-bis(2,2-diphenylvinyl)-1,1′-biphenyl emission layer and a LiF/Al cathode which has an external quantum efficiency of 1.4% and a maximum luminance of 3000 cd/m2. Insertion of the thin LiF layer results in a 50-fold increase in the device efficiency compared to a device with an aluminum only cathode, and eliminates the need for an electron-transporting layer, such as tris(8-hydroxyquinoline)aluminum. This results in a device with excellent color purity with an emission peak at 476 nm and a full width at half maximum of 78 nm. Using ultraviolet photoelectron spectroscopy, we find that the effective work-function of aluminum decreases dramatically with sub-monolayer amounts of LiF deposited on the surface.