Projected Performance of InGaAs/GaAs Quantum Dot Solar Cells: Effects of Cap and Passivation Layers

In this work, the effects of Al
_x
Ga
_1-x
As cap and passivation (such as SiO
₂
, Si
₃
N
₄
, and HfO
₂
) layers on the performance of InGaAs/GaAs-based quantum dot intermediate band solar cells (QDIBSCs) have been studied. The low surface recombination rate of ~10
³
per cm
³
s is achieved by optimizing the composition, x = 0.40, and thickness (200 nm) of the Al
_x
Ga
_1-x
As cap layer. The optical reflectance is also evaluated for devices with different passivation. The solar cell with Si
₃
N
₄
shows the lowest reflectance of 10.53%. The photogeneration rate has been enhanced at the quantum dot region because of the improvement of the photocurrent provides by both cap and passivation layers. There is also an increment found in the average external quantum efficiency of 39.56% as compared to that of the bared conventional QDIBSC. As a result, the solar cell, with both Al
_0.40
Ga
_0.60
As cap and Si
₃
N
₄
passivation layers, shows the conversion efficiency of 27.8%, which is higher than that of 21.6% for conventional In
_0.53
Ga
_0.47
AS/GaAs-based QDIBSC. These results indicate that GaAs-based QDIBSCs with both Al
_0.40
Ga
_0.60
As cap and Si
₃
N
₄
passivation layers are promising for next-generation photovoltaic applications.