Enhancement of electrical conductivity during the femtosecond laser trimming process for OLED repair

• Published in: Optics and lasers in engineering Vol. 137; p. 106381
• Main Authors: Ahn, Sanghoon, Kim, JiHyun, Lee, Dongkeun, Park, Changkyoo, Zander, Christian, Ji, Seok-Young, Chang, Won Seok
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.02.2021
• Subjects: Electrical conductivity; Electrode printing followed by femtosecond laser trimming; Femtosecond laser trimming; OLED display panel repair; Printed electrode; Printed electrode; Electrical conductivity; Femtosecond laser trimming; OLED display panel repair; Electrode printing followed by femtosecond laser trimming
• ISSN: 0143-8166; 1873-0302
• DOI: 10.1016/j.optlaseng.2020.106381

•The electrode printing followed by femtosecond laser trimming (EPFLT) repair process is demonstrated.•The width of electrodes after femtosecond laser trimming are as narrow as 0.81 ± 0.16 µm.•During the EPFLT process, the electrical conductivity is enhanced from 1.51ⅹ107 S/m to 2.31ⅹ107 S/m.•We carefully claim that a heat accumulation and annealing cause the enhancement of the electrical conductivity during the EPFLT. In OLED panel repair process, femtosecond laser ablation has been adopted for last 10 years. Because femtosecond laser process can be performed with negligible thermal effect, it is suitable for modifying the organic materials whose lifetime is negatively affected by heat. Because of it, femtosecond laser ablation process has been applied to repair process of OLED panel such as elimination of internal debris, disconnection of over connected electrodes, and etc. However, it has been limitedly applied to certain types of defects. In order to increase a production yield, various types of defects should be treated. Thus, additive repair process needs to be developed. In last few decades, various research groups have been developing electrode printing techniques. But it is very hard to print an electrode with width of 1 µm scale so far. Therefore, we suggest new repair technique that combines additive and subtractive methods. It is the technique that conductive material is printed with width of few micrometers scale followed by femtosecond laser trimming with width of 1 µm scale. During an electrode printing followed by femtosecond laser trimming (EPFLT) process, we could enhance electrical conductivity of printed electrode. After EPFLT process, the average electrical conductivity of electrodes increases from 1.51ⅹ107 S/m to 2.31ⅹ107 S/m. Here, we carefully claim that the heat accumulation during a femtosecond laser trimming causes an annealing of printed electrode and the electrical conductivity is enhanced.