POLYARYLENE ETHER KETONES AS A CONDUCTOR IN THE SOLAR CELL CURRENT COLLECTION SYSTEM

The paper investigates the thermomechanical and electrical properties of a number of thermoplastic copolymers poly(arylene ether ketones) (co-PAEK) containing fluorene groups in the main chain of the macromolecule. Co-PAEKs are being studied for the purpose of their use in the contact system of a solar cell with a transparent conductive oxide (TCO) electrode and a multiwire contact grid. Polymer films are used as conductive adhesives to form an electrical contact between metal wire and TCO. The formation of an electrically conductive contact occurs during lamination at an excess pressure of 1 atm and a temperature of maximum deformation of co-PAEK, while the copolymer switches from the initial dielectric to a stable highly conductive state. Co-PAEKs with the content of fluorene groups ( q ) 5, 10, 15, 20 and 25 mol.% are synthesized, having the same molecular weight and the reduced viscosity of ~0.38 dl/g. To select the optimal contact system formation temperature for each coPAEK, the glass transition temperature ( T g) and the peak strain temperature ( T d) were determined from thermo mechanical curves. It was found that with increasing q , the temperature T g increases from 162 to 185°С, and T d from 203 to 223°С. The specific contact resistances (ρС) in the metal wire/co-PAEK/TCO (ITO - In2O3:Sn) system were determined for a round copper wire coated with indium:tin (In:Sn) solder, as well as for tin-plated wire, depending on the content of fluorene groups in the copolymer. The specific contact resistance ρС for wire with (In:Sn) solder varies in the range of 0.56-0.83 mΩ cm2, for tin-plated wire - 0.84-1.43 mΩ cm2, and co-PAEK with q = 5 mol % showed the lowest ρС in both cases. The ρC of wire/co-PAEK/ITO contacts has been studied as a function of the resistivity of ITO grown by ultrasonic spray pyrolysis on silicon substrates. The temperature dependence of the resistivity of the wire/co-PAEK/ITO contact was studied in the temperature range of 5-85°C, and a conclusion was made about the metallic type of dependence. According to the results of microscopic studies of the contact area, the typical minimum co-PAEK layer thickness between the wire and ITO after the formation of the contact was determined, which is in the range of 0.5-2.4 μm.