The Role of Spectrum in Encapsulated Bifacial Silicon Heterojunction Solar Cell Carrier Loss

The effect of encapsulant on solar cell performance is widely understood to decrease overall cell power output due to absorption in encapsulating layers. In this work, we quantify the effect of encapsulation across the solar spectrum for high-efficiency bifacial silicon heterojunction solar cells in Synopsys TCAD Sentaurus to determine whether encapsulation causes a significant deviation in current loss trends compared to bare cells. Bare and encapsulated cells are modelled between 300-1200 nm and for air masses (AMs) between 1 and 10.0. Comparing current densities relative to bare cells for front illumination, encapsulation results in a 4.3% increase in parasitic absorption under AM1 illumination, and a 3.9% increase at AM10 as a consequence of the red-shift under higher AM. Despite spectral effects influencing current loss, trends of efficiency with AM are the same for bare and encapsulated cells, peaking around AM5. Encapsulated efficiency is decreased by 1.40 ± 0.02 % abs. compared to bare cells between AM1-10. Thus, while carrier transport is influenced by encapsulation in a wavelength-dependent manner, the overall effect on cell efficiency is a uniform offset for all spectra considered.