Shape Effect of Silicon Nitride Subwavelength Structure on Reflectance for Silicon Solar Cells

In this paper, we, for the first time, examine the spectral reflectivity of hemisphere-, cone-, cylinder-, and parabola-shaped silicon nitride
$(\hbox{Si}_{3}\hbox{N}_{4})$
subwavelength structures (SWSs). A multilayer rigorous coupled-wave approach is advanced to evaluate the reflection properties of
$\hbox{Si}_{3}\hbox{N}_{4}$
SWSs. We optimize the aforementioned four different shapes of SWSs in terms of effective reflectance over a range of wavelength. The results of our paper show that a lowest effective reflectivity could be achieved for the optimized cone-shaped SWS as compared to hemisphere-, parabola-, and cylinder-shaped structures with the same volume. The best shape SWS is then fabricated together with a silicon (Si) solar cell, and the efficiency of the solar cell is compared with that of a solar cell with single-layer antireflection coating (ARC). An increase of 1.09% in cell efficiency
$(\eta)$
is observed for the Si solar cell with a cone-shaped
$\hbox{Si}_{3}\hbox{N}_{4}$
SWS
$(\eta = \hbox{12.86}\%)$
as compared with the cell with single-layer
$\hbox{Si}_{3}\hbox{N}_{4}$
ARCs
$(\eta = \hbox{11.77}\%)$
.