(181bi) Controlled Synthesis of Polyolefin Copolymers with Rapid Curability for Photovoltaic Cell Encapsulation

Authors: 
Luo, L., Zhejiang University
Wang, W. J., Zhejiang University
Li, B. G., Zhejiang University
Zhang, K., Zhejiang University
Liu, P., Zhejiang University
Zhou, G., First Applied Material Co. Ltd
Polymers such as ethylene–vinyl acetate (EVA) copolymers have been widely used as encapsulants in photovoltaic cell modules to prolong their outdoor lifetime. However, EVAs are prone to yellowing after long-term usage, which significantly reduces the photoelectric conversion efficiency of the cells. Alternatively, polyolefins (POs) with outstanding outdoor stability have been considered as a highly promising encapsulant material for the photovoltaic cell encapsulation. The inertness of the POs, however, results in a slow curing during the cell encapsulation process.

In this study, we address the problem through a polymer product engineering approach by controllably introducing pedant vinyl groups into ethylene-octene copolymers via terpolymerization of ethylene, octane-1, and an asymmetric diene. The vinyl functionalities are ready to react with crosslinking agents, which distinctly increases the PO curing rate measured by storage modulus (G’). We are able to precisely tune the vinyl content in the POs from 0 to 4.01 mol% through engineering the polymerization processes. Moreover, under the same crosslinking reaction condition, G’ was significantly increased from 11294 pa to 57090 pa. Interestingly, we also observed that the crosslinking reaction was beneficial to the product transparency and volume resistivity, and did not affect the damp-heat and UV aging performances of the resulting PO films.