Influence of Fundamental Model Uncertainties on Silicon Solar Cell Efficiency Simulations

Abstract

We determine the uncertainties on simulated efficiencies of silicon solar cells due to uncertainties of the fundamental physical models. To determine these, we refit their parameters to the underlying measurement data. Using a metamodeling and Monte Carlo simulation approach, we then deduce how these propagate to the simulated solar cell efficiency. This is evaluated for 150-μm-thick 1 cm p-type standard and advanced silicon passivated emitter and rear cells (PERC), as well as for an ideal silicon solar cell. When sticking to the best-known set of physical models, we determine resulting efficiency uncertainties as low as 0.06% abs for usual PERC cells and 0.1% abs for an ideal cell. In a variance-based sensitivity analysis, we find the uncertainties of the bandgap and the hole density-of-states effective mass as well as the Auger recombination in the limiting case to dominate the efficiency uncertainty. In addition to these relatively low uncertainties, larger discrepancies may arise when applying different physical models for otherwise fixed device properties. We determine comparably large efficiency discrepancies of up to 0.6% abs for the two most prominent bandgap narrowing (BGN) models, and up to 0.15% abs for the two most recent parameterizations of free carrier absorption. We also show evidence that for the specific case of a strong space charge region being present at a recombining surface, Schenk's BGN model fails to replicate experiments. Those discrepancies highlight the necessity of further research on those models. Finally, an error of up to 0.08% abs is observed by simplifying diffused regions on textured surfaces to a planar geometry.

Parasitic photon process versus productive photon process: a theoretical study of free-carrier absorption in conventional and hot-carrier solar cells

“…If the full effectiveness of free-carrier absorption is incorporated in the RN model for hot-carrier solar cells, their maximum efficiencies will almost reach the thermodynamic limit of 85% or so with a carrier temperature of about 2500 K (as shown in figure 8) which is similar to the results predicted for solar thermal converters [3]. Such a resemblance should be expected since the combined results from equations ( 16), (20), and ( 21) also assume that an ideal optical absorber in a hot-carrier solar cell is an ideal black body in which all photons, regardless of their energy, will be completely absorbed by either interband or intraband processes.…”

“…By combining the above results, the relation between the spectral carrier radiative recombination rate r cv (E), the spectral photon flux ϕ cv (E), and the absorption coefficient α dir (E) can be obtained: 20) is an important result. It states that the spectral carrier radiative recombination rate r cv (E) can be calculated from and the absorption coefficient α dir (E) and the spectral photon flux ϕ cv (E).…”

“…This is the reason why free-carrier absorption is commonly identified as a 'parasitic' absorption loss [15][16][17]. Hence, free-carrier absorption is generally believed to be one of the intrinsic physical factors responsible for solar cells unable to achieve their maximum efficiency predicted by the Shockley and Queisser (SQ) theory [18][19][20]. It can cause a detrimental effect which needs be minimized in order to achieve record-breaking efficiencies [21,22].…”