(Georgia Institute of Technology, 2019-07-26)
Li, Jiaxiong
The power electronics industry has been actively seeking encapsulant materials that can serve in harsher environments. For example, with the power semiconductors leading into SiC era, the higher operation temperature (250 ºC) have proposed great challenges on the packaging materials especially on epoxy molding compound (EMC) technologies, since the temperature exceeds the stability limit of typical epoxy (EP) chemistry. In this thesis, EP/triazine system was selected to develop high temperature stable resin system that can meet the temperature requirement of next generation power electronics packaging. In the first part of the thesis, different approaches were discussed to enhance the high temperature performance of a previously studied cyanate ester (CE)/ biphenyl EP blend which is impaired by the hydrolysis degradation of remaining cyanate groups. Firstly, the effects of different metal catalyst on the CE properties were discussed. Secondly, a triazine containing molecule triglycidyl isocyanurate (TGIC) was employed to increase the triazine content without increasing CE feed ratio to circumstance problem of unreacted cyanate groups. Finally, the high heat resistant novolac type CE was employed to form the NCE/EP blend, and their blends with different feed ratio were systematically evaluated. In the second part, a detailed characterization of a high heat resistant CE/novolac type EP blends and the investigation on their degradation under long-term high temperature storage were summarized. The effects of the CE concentration on the thermomechanical properties of the copolymer were explored, where a tradeoff behavior between the triazine content and crosslink density was accounted for the property change. In addition, the distinguished thermal degradation mechanisms in copolymer with different compositions were identified and illustrated. The knowledge obtained in this work can serve as a reference in the future to formulate EP/triazine based resin system for high temperature applications.
(Georgia Institute of Technology, 2019-04-25)
Hah, Jinho
There have been many attempts to improve the stability of the environmentally-sensitive perovskite solar cells (PSCs) from adverse environments. The next generation encapsulation method should be compatible with roll-to-roll (R2R) processing, which can manufacture thin-film PSC modules at large scale and make solar electricity economically competitive with conventional electricity generation. This work investigates the interface chemistry between the polymer backsheet and the polymer encapsulants to understand the moisture, thermal, and UV stability of the packaging materials for PSCs. First, surface modification on the commercially available PET backsheets was done using various types of silane-based coupling agents, and their adhesion profiles were studied upon damp-heat exposure on these samples. Second, thorough XPS analysis was conducted on the delaminated PET surface from the PET/EVA/PET encapsulation architecture upon the UV, thermal, and moisture aging to understand the degradation mechanism at the interface. Moreover, this work also includes encapsulant design by combining the polymer blends to improve the mechanical and chemical bulk properties of a PV encapsulant. In short, this work serves to investigate on the encapsulation methods to improve the reliability and lifetime of PSCs.