Towards self-healing organic electronics
| PhD ceremony: | Mr A.J. (Jolt) Oostra |
| When: | January 04, 2016 |
| Start: | 12:45 |
| Supervisor: | prof. dr. P.W.M. Blom |
| Where: | Academy building RUG |
| Faculty: | Science and Engineering |
Suppression of greenhouse gas emission requires reduction in lighting energy consumption as well as increase in energy production by renewable sources. Organic light-emitting diodes (OLEDs) and organic solar cells (OSCs) are technologies alternative to “classic” crystalline semiconductors that can help in achieving this goal.
OLEDs and OSCs comprise several stacked thin layers that are sandwiched between two metallic contacts (electrodes). As large areas (more than one meter squared) need to be covered with very thin layers (~1000x thinner than a hair), problems can arise that result in the deposition of an incomplete layer. Especially small particles and inhomogeneities on the substrate can easily result in areas where the bottom electrode is not fully covered by the organic material, resulting in short-circuits between the two electrodes. These issues reduce the production output and lead to increased production costs.
In this dissertation methods are described that can be used to prevent short-circuits in OLEDs and OSCs. We show that it is possible to suppress short-circuits in OLEDs and OSCs by using aqueous sodium hypochlorite (bleach) in an additional processing step. We show that leakage currents (usually indicative of microscopic short-circuits) and macroscopic short-circuits (due to large defects in the photoactive layer) can be effectively prevented.
Besides treatment with bleach, we present an alternative method that does not require additional processing steps. We show that by adjusting the cathode in OSCs, it is possible to achieve self-repairing short-circuits. With these results the first steps have been taken in the development of self-healing OLEDs/OSCs