Vinyl-Functionalized Polyolefins for Fast Photovoltaic Cell Encapsulation

Abstract

Polyolefins (POs) are considered a promising candidate for photovoltaic cell encapsulation due to their high volume resistivity, low water-vapor permeability, and outstanding outdoor stability. However, POs without functionalization have a low rate of cross-linking, which significantly slows the solar cell encapsulation process. Herein, we describe the use of a polymer product-engineering approach in which reactive pendent vinyl groups are controllably incorporated in PO polymer chains to accelerate their cross-linking reactions. The POs having limited vinyl functionalities of 0.02−0.37 mol % were synthesized via the copolymerization of ethylene, 1-octene, and vinylnorbornene or 1,9-decadiene at different monomer concentrations. The vinyl groups in the POs readily react with curing agents, increasing crosslinking rates by 14-fold up to 179.7 Pa•s −1 , as measured by the enhancement of the storage modulus (G′). The maximum G′ value representing the melt strength was also increased from 11.3 to 69.0 kPa due to the high curing degree in the POs. The use of a curing agent could be reduced by 50%, and no curing coagent was required in the PO curing process. The vinyl-functionalized POs had a light transmittance of 91%, a good volume resistivity of 7.05 × 10 16 Ω•m, a low water-vapor permeability of 2.31 × 10 −12 g•m•m −2 • s −1 •Pa −1 , and an improved mechanical strength after curing. The damp-heat and UV aging had little effect on their light transmittance. Our approach of synthesizing functional POs with pendent vinyl groups thus promises the development of new highperformance polymer materials for photovoltaic cell encapsulation.

Dynamically Cross-Linked Polyolefin Elastomers with Highly Improved Mechanical and Thermal Performance

“…The obtained v-POEs have good solubility in toluene at 90 °C, and their M w values were determined to be 120–140 kDa with D̵ values between 4.2 and 4.7 according to gel permeation chromatography (GPC) results (Figure S1). The broad D̵ values could be caused by the slight cross-linking of diene monomers. ,, The v-POEs with similar M w and D̵ values and various vinyl contents indicate that only few VNB were dual-inserted. Further characterization of v-POEs with 13 C nuclear magnetic resonance (NMR) spectroscopy showed characteristic carbon signals of 114 and 142 ppm attributing to vinyl of VNB units and 14, 23, and 32 ppm belonging to octylene units (Figures a and S2).…”

“…The broad D̵ values could be caused by the slight cross-linking of diene monomers. 17,21,22 The v-POEs with similar M w and D̵ values and various vinyl contents indicate that only few VNB were dual-inserted.…”

“…We chose an asymmetric diene, 5-vinyl-2-norbornene (VNB), as the third co-monomer in the copolymerization of ethylene and 1-octene. Vinyl-functionalized POEs (v-POEs) are first synthesized using a constrained geometry catalyst ([Me 2 Si­(N t Bu)­(Me 4 Cp)]­TiCl 2 , CGC) and methylaluminoxane (MAO) at 110 °C . The pendant vinyl groups of v-POEs are modified to dihydroxyl groups with thermal- or photoinitiated thiol–ene click chemistry. − The resulted hydroxyl-functionalized POEs (h-POEs) are further cross-linked with bis-dioxaborolane via melt extrusion to form boronic ester cross-linked POEs (BPOEs).…”

Achieving Resistance against Moisture and Oxygen for Perovskite Solar Cells with High Efficiency and Stability

“…Based on the materials of encapsulant, encapsulations are categorized as glass based encapsulation, organic polymer encapsulation, and inorganic thin film encapsulation. ,, The glass based encapsulation possesses significant advantages, such as easy operation, impressive durability, and high serviceability under outdoor conditions. A variety of materials have been adopted in this encapsulation process for effective protection, including ethylene vinyl acetate (EVA), polyurethane (PU), polyisobutylene, and polyolefin (POE). − However, this encapsulation method is not applicable to flexible devices, and furthermore the migration of Na + ions in glass induces potential degradation.…”

Engineering Ethylene/1-Hexene Copolymers from Ethylene Stock with a Model-Guided Catalyst Feeding Policy

“…Ethylene/α-olefin copolymers, including linear low-density polyethylenes (LLDPEs) and polyolefin thermoplastic elastomers (POEs) produced by random copolymerization of ethylene and higher α-olefins, have been widely used in automotive, wire and cable, electronic, and other industries owing to their outstanding mechanical properties and relatively low cost. − The increase of α-olefin content in the copolymers gradually transforms the materials from a high-density polyethylene to a LLDPE, plastomer, and POE . At a given α-olefin content, the performance of the copolymers is highly dependent on their chain compositions and distributions, − which determine the crystalline structures of the polymers such as lamella sizes and distributions.…”