Modeling and Analysis of Vertical p-n Junction, Graded Bandgap AlfGa1–fAs Rectangular-Slab and Cylindrical Solar Cells on Elevated GaAs Ridge and Wire

This paper conceptualizes vertical junction, graded bandgap Al
_f
Ga
_1-f
As rectangular-slab and cylindrical solar cells. The cells are analyzed through numerical modeling under drift-diffusion transport framework. We find that, these special cells can significantly increase photocurrent density due to asymmetry between light receiving and electrical contact areas, while at the same time bandgap grading within quasi-neutral regions enables both near band edge and short wavelength absorption. Under AM 1.5G, 1000-W/m
²
illumination to the light receiving area (hence, electrical contacts receive 32 sun power during actual photo conversion), we find that rectangular-slab cells can outperform cylindrical cells of identical dimension and exhibit maximum 529.8 mA/cm
²
short circuit current density, 1 V open circuit voltage and 0.88 fill factor when maximum aluminum mole fraction is fixed at 0.175, and band gap grading is fixed within 15.24 and 3.81 μm from respective depletion edges (p and n). Furthermore, we find that through a combination of bandgap grading and mole fraction tailoring, maximum 4.91 × 10
⁴
and 1.96 × 10
⁵
V/m (p and n) built-in fields can be achieved, when bandgap grading is made in 0.05and 0.2-eV/μm (p and n) steepness, which results in 46.8 percent efficiency in graded rectangular-slab cells.