Abstract:
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.
