Raytracing Modelling of Infrared Light Management Using Molybdenum Disulfide (MoS2) as a Back-Reflector Layer in a Silicon Heterojunction Solar Cell (SHJ)

Abstract

The silicon heterojunction solar cell (SHJ) is considered the dominant state-of-the-art silicon

solar cell technology due to its excellent passivation quality and high efficiency. However, SHJ’s light

management performance is limited by its narrow optical absorption in long-wave near-infrared (NIR)

due to the front, and back tin-doped indium oxide (ITO) layer’s free carrier absorption and reflection

losses. Despite the light-trapping efficiency (LTE) schemes adopted by SHJ in terms of back surface

texturing, the previous investigations highlighted the ITO layer as a reason for an essential longwavelength

light loss mechanism in SHJ solar cells. In this study, we propose the use of Molybdenum

disulfide (MoS2) as a way of improving back-reflection in SHJ. The text presents simulations of

the optical response in the backside of the SHJ applying the Monte-Carlo raytracing method with

a web-based Sunsolve high-precision raytracing tool. The solar cells’ electrical parameters were also

resolved using the standard electrical equivalent circuit model provided by Sunsolve. The proposed

structure geometry slightly improved the SHJ cell optical current density by ~0.37% (rel.), and hence

efficiency (h) by about 0.4% (rel.). The SHJ cell efficiency improved by 21.68% after applying thinner

back ITO of about 30 nm overlayed on ~1 nm MoS2. The efficiency improvement following the

application of MoS2 is tentatively attributed to the increased NIR absorption in the silicon bulk due

to the light constructive interface with the backside components, namely silver (Ag) and ITO. Study

outcomes showed that improved SHJ efficiency could be further optimized by addressing front cell

components, mainly front ITO and MoS2 contact engineering.