화학공학소재연구정보센터
Solar Energy Materials and Solar Cells, Vol.165, 1-8, 2017
Transparent conductive polymers for laminated multi-wire metallization of bifacial concentrator crystalline silicon solar cells with TCO layers
Replacing expensive silver with inexpensive copper for the metallization of silicon wafer solar cells can lead to substantial reductions in material costs associated with cell production. A promising approach is the use of multi-wire design. This technology uses many wires in the place of busbars, and the copper wires are "soldered" during the low-temperature lamination process to the fingers (printed or plated) or to the transparent conductive oxide (TCO) layer, e.g. in the case of the a-Si:H/c-Si heterojunction cells. Here we describe a solar cell design in which wires are attached to TCO layers using transparent conductive polymer (TCP) films. To this end, we have synthesized a number of thermoplastics, poly(arylene ether ketone) copolymers (co-PAEKs), containing phthalide in their main chain. The fraction of phthalide-containing units in the copolymers was p=3, 5, 15, and 50 mol%. With increasing p, the peak strain temperature of the co-PAEKs rises from 205 to 290 degrees C and their optical band gap and refractive index increase from 3.12 to 3.15 eV and from 1.6 to 1.614, respectively. The copolymers have a negligible absorption coefficient in the wavelength range 400-1100 nm. When exposed to an excess pressure of 1 atm or above, co-PAEK films less than 30 mu m in thickness undergo a transition from a dielectric to a conductive state. The resistivity (rho c) of wire/TCP/TCO (ITO=In2O3:Sn and IFO=In2O3:F) contacts ranges from 0.37 to 1.43 m Omega cm(2). The polymer with the highest phthalide content (p=50 mol%) has the lowest pc. The average work of adhesion per unit area determined by pulling off the wires from the polymer surface depends on both the phthalide content of the co-PAEKs and their reduced viscosity, ranging from 14.3 to 43.5 N/cm. The highest value was obtained for the co-PAEK with p=50 mol%. We have fabricated low-concentration bifacial IFO/(n(+)pp(+))Cz-Si/ITO solar cells with a wire contact grid attached to IFO and ITO using a co-PAEK film. The efficiency of the best cell under 1x to 7x front/rear illumination was determined to be 18.3-18.9%/15.0-15.6%.