A new proposal for the extraction of the shunt resistance ( R _sh ) and saturation current ( I _sat ) of a current-voltage (I–V) measurement of a solar cell, within the one-diode model, is given. First, the Cheung method is extended to obtain the series resistance ( R _s ), the ideality factor ( n ) and an upper limit for I _sat . In this article which is Part 1 of two parts, two procedures are proposed to obtain fitting values for R _sh and I _sat within some voltage range. These two procedures are used in two simulated I–V curves (one in darkness and the other one under illumination) to recover the known solar cell parameters R _sh , R _s , n , I _sat and the light current I _lig and test its accuracy. The method is compared with two different common parameter extraction methods. These three procedures are used and compared in Part 2 in the I–V curves of CdS-CdTe and CIGS-CdS solar cells.

The cadmium sulfide (CdS) n-type semiconductor is one of the most used as a window layer in thin-film solar cells, such as CdTe, CIS, CIGS, and CZTS. Optoelectronic properties are the most important characteristics for window materials. CdS thin films obtained using the chemical bath deposition technique (CBD) have been reported; however, large amounts of precursor solutions are used, which generate considerable amounts of toxic waste. The aim of this work is to reduce the amount of precursor solutions used for CdS growth; for this, it is necessary to consider an efficient position for the substrate inside the reactor container and at the same time allow obtaining CdS thin films with adequate physical properties to be applied in the photovoltaic solar cell development. CdS thin films were deposited on soda-lime/SnO₂:F substrates (FTO) using the CBD technique; the substrates were placed in three different arrangements [rack system, step system (up), and step system (down)]. CdS samples with areas of 4 cm² and a thickness of 27-48 nm were obtained; the X-ray diffraction patterns show CdS thin films with different polycrystalline structures. The morphological measurements reveal different surface formations depending on the substrate position, and resistivity values of around 10⁵ Ω*cm were measured. UV-vis spectra show transmittance values of around 45-94% in the visible region with band gap energy values of around 2.1-2.36 eV. The best physical properties of CdS thin films and an efficient CBD process were obtained when the FTO substrates were located near the bottom of the reactor container with the FTO side down, leading to an optimal configuration that allows reducing the amount of precursor solutions and in this way reduces the toxic waste generated. These results are important in the photovoltaic technology process and environmental impact.

In this Part 2 of this series of articles, the procedure proposed in Part 1, namely a new parameter extraction technique of the shunt resistance ( R _sh ) and saturation current ( I _sat ) of a current-voltage ( I – V ) measurement of a solar cell, within the one-diode model, is applied to CdS-CdTe and CIGS-CdS solar cells. First, the Cheung method is used to obtain the series resistance ( R _s ) and the ideality factor n . Afterwards, procedures A and B proposed in Part 1 are used to obtain R _sh and I _sat . The procedure is compared with two other commonly used procedures. Better accuracy on the simulated I – V curves used with the parameters extracted by our method is obtained. Also, the integral percentage errors from the simulated I – V curves using the method proposed in this study are one order of magnitude smaller compared with the integral percentage errors using the other two methods.