Investigation of Base High Doping Impact on the npn Solar Cell Microstructure Performance Using Physically Based Analytical Model

Abstract

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 2×10 19 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 5×10 17 cm-3 to 2×10 19 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 Investigation of a Proposed Flipped npn Microstructure Silicon Solar Cell Using TCAD Simulation

“…where N ref = 5 × 10 16 cm −3 and N p+,base = 10 18 cm −3 , and the constant γ is assumed to be 0.5 [20]. For the simulated heavily doped wafers, the bulk lifetime τ no was assumed to be in the range of 1 µsec-40 µsec [42,43].…”

“…To overcome such a problem, the light-generated carriers in such inexpensive wafers need to be vertically generated and laterally collected [18]. Such an idea opens a route for employing low-quality highly doped Si wafers, which are characterized by their low cost and commercial availability for solar cell fabrication [19,20]. Recently, a proposed npn microstructure SC, which was based on a heavily doped Si wafer as a base material, demonstrated an initial efficiency of 10.7% [21].…”

Gold Nanoparticles Introduced ZnO/Perovskite/ Silicon Heterojunction Solar Cell

“…The industry mainly produces silicon-based solar cells [1]. Although, lots of scientific work has been done to optimize the size [2], surface morphology [3], doping concentration [4] and device structure of silicon-based solar cells, silicon-based solar cells are still considered to have high production cost along with a modest efficiency of 22.8% [5]. In addition, the efficiency of pure silicon-based solar cells cannot exceed the theoretical value of 29% according to the Shockley-Quisser…”