RESUMO
The silicon heterojunction solar cell (SHJ) is considered the dominant state-of-the-art silicon solar cell technology due to its excellent passivation quality and high efficiency. However, SHJ's light management performance is limited by its narrow optical absorption in long-wave near-infrared (NIR) due to the front, and back tin-doped indium oxide (ITO) layer's free carrier absorption and reflection losses. Despite the light-trapping efficiency (LTE) schemes adopted by SHJ in terms of back surface texturing, the previous investigations highlighted the ITO layer as a reason for an essential long-wavelength light loss mechanism in SHJ solar cells. In this study, we propose the use of Molybdenum disulfide (MoS2) as a way of improving back-reflection in SHJ. The text presents simulations of the optical response in the backside of the SHJ applying the Monte-Carlo raytracing method with a web-based Sunsolve high-precision raytracing tool. The solar cells' electrical parameters were also resolved using the standard electrical equivalent circuit model provided by Sunsolve. The proposed structure geometry slightly improved the SHJ cell optical current density by ~0.37% (rel.), and hence efficiency (η) by about 0.4% (rel.). The SHJ cell efficiency improved by 21.68% after applying thinner back ITO of about 30 nm overlayed on ~1 nm MoS2. The efficiency improvement following the application of MoS2 is tentatively attributed to the increased NIR absorption in the silicon bulk due to the light constructive interface with the backside components, namely silver (Ag) and ITO. Study outcomes showed that improved SHJ efficiency could be further optimized by addressing front cell components, mainly front ITO and MoS2 contact engineering.
RESUMO
COVID-19 has had a significant impact on the global demand and consumption of energy. In particular, the effect of the lockdown measures due to the COVID-19 pandemic can be seen directly in the reduced energy consumption in educational buildings. Therefore, the objective of this study is to assess the impact of COVID-19 on the electricity use in university buildings. The Research Complex Building of the National University of Malaysia was selected as a case study. An energy audit analysis was conducted based on the data collection via walk-through field audits and data loggers during the normal year (2019) to establish a baseline of data. The comparison of the electricity pattern during the normal year with the lockdown period of 2020 shows that the Building Energy Index (BEI) during a pandemic decreased by approximately 11% from the BEI in the normal year. In this regard, the energy audit verified that the main factors of electricity consumption are occupant presence and energy use in buildings. Hence, on the basis of the energy audit results, three appropriate energy conservation measures (ECMs) were detected and subsequently proposed to minimise the waste of energy. Results show that the implementation of ECMs can improve the energy consumption of buildings and reduce energy consumption by 21.81% or approximately 19% from the normal year. Hence, efficient energy use in buildings in the post-pandemic period can be achieved by the implementation of all the ECMs proposed.
