Ewald Karl Michael Guenther

A mechanical assessment of flexible optoelectronic devices

This work has demonstrated novel experimental methods and their relevant analysis to evaluate the fracture properties of thin brittle films on compliant substrates for flexible optoelectronic devices. Based on the understanding of the failure mechanisms, mechanical calculation has been provided to estimate the thin film fracture toughness and film delamination toughness. These values serve as design parameters on the device flexibility and reliability.

Optimized indium tin oxide contact for organic light emitting diode applications

This work aimed to develop indium tin oxide (ITO) coatings with optimum optoelectronic properties required for applications in organic light emitting diode (OLED) devices on flexible thin glass substrates. This involved introducing hydrogen in gas mixture during ITO film preparation using radio frequency magnetron sputtering method. Uniform ITO films with resistivity of 2:7 £ 10; 24 Vcm and transparency of 85% over the visible wavelength region was achieved. The presence of hydrogen gas in the sputtering processes was shown to increase the number of charge carriers in the ITO films. The feasibility of using the ITO films with high carrier concentration was examined and tested in OLED devices composing a fluorene based polymeric hole transporting layer (HTL) and green-emitting polymer, benzothiadiadzolefluorene. The devices made with different ITO substrates had an identical configuration of ITO/HTL/emitter polymer/Ca (6 nm)/Ag (200 nm). The device showed that a maximum luminance of 4:36 £ 10 4 cd/m 2 and an efficiency of 4.14 cd/A were achieved when an optimal ITO layer was used. These results are comparable with that of devices made with the best commercially available ITO products operated at the same conditions. q 2000 Elsevier Science S.A. All rights reserved.