Colloquia

Summary

Solar photovoltaics (PV) constitute a mature and widely used optoelectronic technology. Their expansion has been accelerated globally as a result of energy transition and decarbonization policies. In addition, the abundance of low-cost crystalline Si cells and modules has been the major driver for the deployment of large-scale PVs. Although their prices have undergone a noticeable decline, the cost of PV-generated electricity has become more and more dependent on components not directly related to the module, which are not expected to be substantially decreased in the near future. Hence, improving the efficiency of solar cell modules emerges as the only realistic cost-reducing alternative. Namely, higher power outputs can lead to lower dollar per Watt prices. To this end, optimal photon management is deemed critical. In this context, even higher solar cell efficiencies can be achieved by improved front contact designs. In the case of conventional solar cells, a fraction of the incident solar radiation is immediately lost at the front contacts either through absorption caused by transparent conductive oxides or via reflection at grid fingers. Diverse novel design alternatives have already emerged in the corresponding literature, aiming to alleviate front contact losses. In the current thesis, a different approach is presented and investigated. More specifically, losses are mitigated by high aspect ratio, triangular cross-section front contacts, formulated by means of string-printing. Such front contacts are capable of redirecting the incoming light more efficiently towards the active area of the solar cell. After a detailed analysis of the string-printing method and the related equipment used in the process, the actual incurred improvement in the overall efficiency is measured using a solar simulator, in order to define the I-V curves of the new proposed design. More precisely, the analysis consists of three pillars, namely Design, Sustainability and Socio-Economics, each of which corresponds to a related research question.

• Design: Which parameters are critical for achieving the optimal front contact geometry and what are their desired values?

• Sustainability: How much is solar cell efficiency improved according to the I-V curves generated by the experiment?

• Socio-Economics: To what extent does the efficiency improvement reduce the Levelised Cost of Energy (LCOE) for solar PVs