Solar cell parameters extraction, with less than 10 % error, refining the Co-Content function through an integration of a polynomial fit of I-Isc, in the case of constant percentage noise, and a percentage noise of the maximum current, Imax. Part 1: theoretical analysis and proposal

Abstract In this Part 1 article of this series of articles, a new methodology to refine the Co-Content function \((CC(V,I))\) is proposed, consisting on fitting the current minus the short-circuit current \((I-{I}sc)\), to an \(N-1\) order polynomial, where \({N}ₚₒᵢₙₜₛ=N\), is the number of measured current-voltage \((IV)\) points, and integrating it to calculate \(CC(V,I)\). The shunt resistance \(({R}ₛₕ)\), the series resistance \(({R}ₛ)\), the ideality factor \((n)\), the light current \(({I}lig)\), and the saturation current \(({I}ₛₐₜ)\), are then deduced, in the case of a constant percentage noise or a percentage noise of the maximum current \(({I}ₘₐₓ)\). In the former case, \({R}ₛ\), \({R}ₛₕ, n, and {I}lig,\) can be deduced with less than 10% error, using only \({P}V=\)51 \(number of points/V\), even if the noise is as large as \({p}ₙ=0.1 %\), with a computation time around 80 ms. \({I}ₛₐₜ\) needs \({p}ₙ=0.05 %\) or less, and \({P}V\) equal or larger than 501 \(number of points/V\). For the latter case, \({R}ₛ\), \(and {I}lig,\) can be obtained with less than 10% error, using only \({P}V=\)251 \(number of points/V\), and \({p}ₙ=0.1 %\), or smaller, with total computation time around 49 s. \({R}ₛₕ, {I}ₛₐₜ, and n\) needs that \({p}ₙ≤ 0.05 %\), and \({P}V=\) 751 \(number of points/V\) or larger. A computation time expression of the form \(time=E{{N}ₚₒᵢₙₜₛ}ᵐ\), is deduced. The methodology proposed in this article is appliable to unevenly/randomly distributed IV data points, and it is implemented in Part 2 in solar cells’ and photovoltaic modules’ experimental \(IV\) reported in the literature, to deduce their five solar cell parameters.