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Optimising the fabrication of organic light-emitting diodes by laser-induced forward transfer
| Content Provider | Semantic Scholar |
|---|---|
| Author | Stewart, James Shaw |
| Copyright Year | 2012 |
| Abstract | Laser-induced forward transfer (LIFT) has been used to print different types of organic lightemitting diode (OLED) pixels: Polymeric OLEDs (PLEDs), small molecule OLEDs (SMOLEDs), and phosphorescent OLEDs (PhOLEDs). The LIFT process uses an intermediate dynamic release layer (DRL) to provide the propulsion force. The DRL material is a triazene polymer (TP), which decomposes, at least in part, photochemically meaning that thermal build-up is limited. The use of LIFT for all types of thin-film OLED materials has been enhanced by the reduction of the environmental pressure and the introduction of a well-defined donorreceiver substrate gap. In addition, theoretical insights into the LIFT process have been obtained through both experiments and numerical simulations, which look particularly at the flyer velocity, laser pulse length and thermal effects. Fundamental analysis into TP ablation and the LIFT process has been investigated in a number of different ways. Two analytical modelling approaches have been outlined for UV TP ablation: a thermal model which has been used to evaluate the proportion of heat lost into the substrate for both frontside and backside ablation, and a flyer velocity model based on the explosive Gurney model. The model is compared to velocity results obtained at reduced pressure from shadowgraphy, and the large loss in energy from the laser to the flyer has been compared with the thermal energy in the substrate from the thermal model. TP ablation with different laser pulse lengths shows that shorter pulse lengths give a lower ablation depth per pulse, suggesting smaller thermal energy losses for shorter pulse lengths when analysed using the thermal model. Thermal ablation has been investigated experimentally by ablation of TP films using pulsed laser heating of a silicon substrate, and measuring the flyer by reflectometry. Complementing the theoretical understanding of the LIFT process, pixel deposition of various types of OLED pixels (known as LIFTed pixels) has been optimised. LIFT of both Al / poly(2-methoxy-5-(2’-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) and Ag / poly(9,9-dioctylfluorene-2,7-diyl) (PFO) bilayer pixels, at atmospheric pressure, has been improved by modification of the receiver substrate to improve interfacial adhesion. Early successes with Al / MEH-PPV pixels at atmospheric pressure have been followed up by studies into the effects of a reduction in the environmental pressure and variation of the donorreceiver gap with a spacer. The reduction of atmospheric pressure, combined with a controlled donor-receiver gap of∼ 15 μm, has been used to deposit a number of different types of OLEDs: tri-colour PFO-based PLEDs and PhOLEDs; aluminium tri-8-hydroxyquinoline |
| File Format | PDF HTM / HTML |
| DOI | 10.3929/ethz-a-007321555 |
| Alternate Webpage(s) | https://www.research-collection.ethz.ch/bitstream/handle/20.500.11850/63324/eth-5734-02.pdf?isAllowed=y&sequence=2 |
| Alternate Webpage(s) | https://www.research-collection.ethz.ch/bitstream/handle/20.500.11850/63324/eth-5734-01.pdf?isAllowed=y&sequence=1 |
| Alternate Webpage(s) | https://www.research-collection.ethz.ch/bitstream/handle/20.500.11850/63324/eth-5734-02.pdf |
| Alternate Webpage(s) | https://doi.org/10.3929/ethz-a-007321555 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
