| AVS 63rd International Symposium & Exhibition | |
| Advanced Surface Engineering | Tuesday Sessions |
| Session SE+MS+TF-TuA |
| Session: | Innovations in PVD, CVD, Atmospheric Pressure Plasma and Other Surface Technologies |
| Presenter: | Omar K. Abudayyeh, University of New Mexico |
| Authors: | O.K. Abudayyeh, University of New Mexico N.D. Gapp, Air Force Research Laboratories G.K. Bradshaw, Air Force Research Laboratories D.M. Wilt, Air Force Research Laboratories S.M. Han, University of New Mexico |
| Correspondent: | Click to Email |
Microcracks developing in photovoltaic cells, due to growth defects or due to external mechanical factors, can lead to substantial power loss in solar cells. Microcracks can be critical as they propagate from the semiconductor bulk to the metal gridlines isolating portions of the cell and leading to decreased cell performance. In this work, multiwalled carbon nanotubes are being investigated for reinforcement of metal contacts on photovoltaic solar cells that serve as a secondary conductive network in the presence of cracks. In this effort we have focused on a silver-carbon-nanotube layer-by-layer microstructure. We present the use of a simple, cost-effective, and manufacturable method of depositing carbon nanotubes onto electroplated metal films to create metal matrix composite gridlines for photovoltaic cells. Carbon nanotubes are deposited using a spray coating method to create layer-by-layer microstructure composites. To increase adhesion strength to metal and achieve efficient metal-nanotube stress transfer, carbon nanotubes are chemically functionalized with carboxylic group prior to deposition. Initial strain failure tests show the ability of composite lines to remain electrically connected with fractures up to 28-µm-wide on average, where carbon nanotubes electrically bridge the gap. The metal-carbon-nanotube composites are electrically characterized though current-voltage (I-V) sweeps. Our composite lines can carry current densities ranging from 500 to 2500 A/cm2 in the presence of cracks (5, 10, and 15-μ m-wide). MMC gridlines are successfully integrated on commercial triple-junction solar cells with measured fill factor and efficiency 86% and 26.8% respectively, closely comparing to current triple-junction cells with standard metallization. Dark I-V measurements indicate further improvement in the series and shunt resistances of the cells with the optimization of MMC integration process.