Organic electronics have been highlighted because of their outstanding advantages such as solution process, light weight, fast and flexibility compared with conventional electronics. Therefore, conventional electronics have been transformed to organic material based electronics which can endure various mechanical loadings. However, current organic electronics have critical problems with their low fracture resistance, environmental stability and defects evolution under mechanical loadings. In this dissertation, I have focused on evaluation of the weak interfacial reliability of organic electronic materials and the simultaneous improvement with efficien-cy. To investigate the interfacial reliability, double cantilever beam (DCB) fracture mechanics testing was employed. Also, four different enhancing methods are introduced. First method is a using an additive into organic electronic material in the state of solution to change the polymer conformation. Second method is surface treatments on the spin coated organic electronic material thin films to alter the surface energies. Third method is introduction of adhesive layer at the weak interface. The last is a method of strengthening by forming fibrils in an organic electronic material.
Through adopting the enhancing methods, the cohesion and electrical conductivity of conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) which has low cohesion by weak hy-drogen bonding were improved by adding dimethyl sulfoxide (DMSO) and $H_2SO_4$ treatment. Also the significant changes in the mechanical and electrical properties that are dependent on the concentration of DMSO and $H_2SO_4$ were demonstrated. In addition, the enhancement mechanism of adhesion and efficiency in PCDTBT-based organic solar cells (OSCs) was studied by controlling the surface wettability at the interface between buffer and active layers. Depending on surface treatments on ZnO layer, adhesion and crack path are changed indicating that surface wettability affects to interfacial characteristics. In perovskite solar cells, mechanical stability of perovskite solar cell was investigated through the adhesion changes by ion additives under humid environments and the correlation between additives, adhesion and delamination was demonstrated. Also, to make difficult the crack propagation at the weak interface, surface roughness control of perovskite layer and fibril formation in organic electronic materials were conducted.
유기전자는 용액 공정을 통해 제작 됨으로써 기존의 전자 방식보다 공정이 빠르고, 디바이스의 무게가 가벼우며, 유기전자재료 사용을 통해 기계적으로 유연함을 가지는 장점이 있다. 따라서 기존의 전자 방식은 굽힘, 인장 및 비틀림 등 다양한 기계적 하중에 노출되어야 하는 웨어러블 전자의 흐름에 맞춰 유기전자로 변모해 왔다. 하지만 유기전자의 주 재료로 사용되는 유기재료는 물질 자체 특성상 내부결합력이 매우 약해 외부 하중이나 환경노출에 취약하기 때문에 현재 유기전자에 기대되는 기계적 하중을 효율을 유지해내면서 견뎌내기가 어렵다. 본 학위논문에서는 유기전자재료의 약한 계면 접합 신뢰성을 평가하고 효율과 동시에 향상시키는 방법을 다루고자 한다. 계면 접합 신뢰성을 평가하기 위해서 본 연구에서는 더블 캔틸레버 빔 테스트라는 파괴역학 기반의 실험방법을 사용하였다. 향상시키는 방법으로는 크게 네 가지로 접근하였으며 용액 상태인 유기전자재료 내에 첨가제를 넣어 폴리머 체인형상을 변화시키는 방법, 박막 상태인 유기전자재료 표면에 표면처리를 하여 표면에너지를 변화시키는 방법, 약한 계면에 접합력이 좋은 새로운 물질을 도입하는 방법, 마지막으로는 유기전자재료 내에 피브릴을 형성시켜 강화시키는 방법이다.
