Won Jin Kim

We report a method to fabricate tailored transparent electrodes using photopatternable transparent conducting oxide nanoparticles (TCO NPs). We demonstrate solution-processed micropatterns by a conventional photolithography technique. We have synthesized indium tin oxide (ITO) NPs and functionalized them with a photolabile group, such as t-butoxycarbonyl (t-BOC), which can be deprotected by a chemical amplification reaction in the solid state film. The chemical amplification reaction leads to a shortening of the ligand that changes the solubility of the resulting ITO films. This ligand shortening process also contributes to a reduction of the sheet resistance in the resulting photopatterned ITO films. Furthermore, we have demonstrated the general viability and strength of this approach by also photopatterning zinc oxide (ZnO) NPs.

Successful integration of solution-processible nanocrystal quantum dots, active over a wide spectral range in the infrared, organic molecules and polymers, to fabricate efficient photoconductive and photorefractive devices operational at important optical communication wavelengths is achieved. Sensitization of the polymeric composites by quantum dots led to high photocurrents at 1340 nm, yielding a high photoconductive quantum efficiency. In the photorefractive composites, pronounced two-beam coupling was observed, leading to good optical gains achievable by low-power continuous-wave illumination. The photoresponse was further extended to 1550 nm. A steady state diffraction efficiency was obtained in the dynamic refractive-index gratings with appreciable response times. In order to enhance the photoconductive performance of the devices, the organic semiconductor pentacene was incorporated into the hybrid composite through a soluble presursor. At the operating wavelength of 1340 nm, the photocurrent increased significantly as the amount of pentacene in the composite was increased, resulting in a spectacular improvement of external quantum efficiency.