For the long-term strategy of gradual decarbonization of the world’s energy supply, high penetration of PV electricity is critical in the future world energy landscape. In order to achieve this, solar electricity with competitive cost to fossil fuel energy is necessary. To be able to obtain high efficiency solar cells, many advanced cell architectures have been developed commercially by PV industry. However, the fabrication of these cells necessitates complex processing steps and high requirements on semiconductor materials, which make it not as cost-effective as the state-of-the-art conventional Al-BSF structure. In order to keep the cost of PV cell low and improve on the efficiency with fewer processing steps, this thesis work focuses on the understanding of the conventional Al-BSF solar cell structure. The research work therefore, focuses on the (i) design, and modeling of front metal electrodes including the use of multi-bus-bar capable of decreasing the gridline resistance, (ii) fine-line printing and (iii) metal contact co-firing using high belt speed that is not common to the solar industry to achieve ~20% efficient industrial Al-BSF silicon solar cells.
In order to achieve the objectives of this thesis work, firstly, the appropriate Al paste was investigated for lowest back surface recombination velocity (BSRV), which gives high open circuit voltage (Voc). Secondly, the impact of emitter sheet resistance on solar cell performance was modeled to determine the optimal sheet resistance, and the uniformity of emitter was also investigated. Thirdly, modeling on the front metal electrodes was carried out to investigate the optimal number of busbars, and determine the optimum number of gridlines and gridline geometries that would result in low series resistance (Rs), high fill factor (FF) and hence high efficiency. Fourthly, the modeled results were experimentally validated through fine-line printing and optimized contact co-firing. By combining each layer to make solar cells, Voc of ~642 mV, Jsc of ~38.5 mA/cm 2 and FF of ~80.4% led to average ~19.8% efficient cell. Based on the experimental results, other innovative front grid designs are proposed that can lead to >20% energy conversion efficiency.
|Commitee:||Raja, Yasin, Schmitz, Tony, Stokes, Edward B., Zhang, Yong|
|School:||The University of North Carolina at Charlotte|
|School Location:||United States -- North Carolina|
|Source:||DAI-B 77/01(E), Dissertation Abstracts International|
|Subjects:||Electrical engineering, Energy|
|Keywords:||Al-bsf, Fine-line printing, Gridline segmentation, Multi-busbar, Silicon solar cell, Uneven busbar|
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