Browsing by Author "Marwa S, Salem"

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Investigation of Base High Doping Impact on the npn Solar Cell Microstructure Performance using Physically Based Analytical Model
(IEEE, 2021-01) Marwa S, Salem; Zekry, Abdelhalim; Shaker, Ahmed
Recently, there is a rapid trend to incorporate low cost solar cells in photovoltaic technology. In this regard, low-cost high-doped Silicon wafers are beneficial; however, the high doping effects encountered in these wafers render their practical use in fabrication. The npn solar cell microstructure has been found to avoid this issue by the proper design of vertical generation and lateral collection of the light generated carriers. We report on the impact of the p+ base doping concentration, up to 2×1019 cm-3, on the npn microstructure performance to find the most appropriate way for high efficiency. To optimize the structure, a series of design steps has been applied using our previously published analytical model. Before inspecting the high doped base effect, firstly, the n+ emitter is optimized. Secondly, the impact of bulk recombination inside the p+ base is introduced showing the range of optimum base width (Wp). Then, we investigate thoroughly the impact of base doping levels for different base widths to get the optimum Wp that satisfies maximum efficiency. The results show that for p+ base doping concentration ranging from 5×1017 cm-3 to 2×1019 cm-3, the npn microstructure efficiency decreases from 15.9% to 9%, respectively. Although the efficiency is degraded considerably for higher doping levels, the structure still achieves a competitive efficiency at higher doping levels, for which its cost is greatly reduced, in comparison with thin film solar cells. Moreover, using higher doping permits lesser wafer area which could be beneficial for large area solar cells design.
Performance Improvement of npn Solar Cell Microstructure by TCAD Simulation: Role of Emitter Contact and ARC
(Multidisciplinary Digital Publishing Institute (MDPI), 2022-09) Marwa S, Salem; Zekry, Abdelhalim; Shaker, Ahmed; Abouelatta, Mohamed; Almurayziq, Tariq S; Alshammari, Mohammad T; El-Banna, Mohamed M
In the current study, the performance of the npn solar cell (SC) microstructure is improved by inspecting some modifications to provide possible paths for fabrication techniques of the structure. The npn microstructure is simulated by applying a process simulator by starting with a heavily doped p-type substrate which could be based on low-cost Si wafers. After etching deep notches through the substrate and forming the emitter by n-type diffusion, an aluminum layer is deposited to form the emitter electrode with about 0.1 µm thickness; thereby, the notches are partially filled. This nearly-open-notches microstructure, using thin metal instead of filling the notch completely with Al, gives an efficiency of 15.3%, which is higher than the conventional structure by 0.8%. Moreover, as antireflection coating (ARC) techniques play a crucial role in decreasing the front surface reflectivity, we apply different ARC schemes to inspect their influence on the optical performance. The influence of utilizing single layer (ZnO), double (Si3N4/ZnO), and triple (SiO2/Si3N/ZnO) ARC systems is investigated, and the simulation results are compared. The improvement in the structure performance because of the inclusion of ARC is evaluated by the relative change in the efficiency (∆η). In the single, double, and triple ARC, ∆η is found to be 12.5%, 15.4%, and 17%, respectively. All simulations are performed by using a full TCAD process and device simulators under AM1.5 illumination.