Device Design and Photovoltaic Performance of Heterojunction Solar Cells Using Ultra-Thin Bi2S3 Photoabsorber

In this work, we report on the device design and numerical simulation results on the characteristics of Cu-doped p-type Bi
₂
S
₃
-based ultra-thin film solar cells. Potential non-toxic, wide-bandgap n-type semiconductors including ZnS, TiO
₂
, ZnO:Al, and In
₂
S
₃
were investigated as window layers in this study. Device simulation was performed using Solar Cell Capacitance Simulator (SCAPS) and photovoltaic performance parameters, such as open-circuit voltage (V
_OC
), short-circuit current density (J
_SC
), fill factor (FF), and photoconversion efficiency (PCE) were studied. The best-performing devices were obtained with p-Bi
₃
S
₃
/n-In
₂
S
₃
heterojunction structure while p-Bi
₃
S
₃
/n-TiO
₂
lead to inferior performance due to mismatch in the band alignment. A respectable efficiency of 17.1% was obtained with an absorber layer thickness of 1 μm with In
₂
S
₃
as the window layer and >16% PCE was achieved with ZnO:Al as the n-type heterojunction partner. Our findings clearly show the potential of p-type Bi
₂
S
₃
as an active absorber layer and suggests that high efficiency thin film solar cells can be fabricated with this novel solar cell photoabsorber at a much lower cost and without any toxicity issues.