Extraction of diode parameters of silicon solar cells under high illumination conditions Firoz Khan, Seong-Ho Baek, Yiseul Park, Jae Hyun Kim ⇑ Energy Research Division, Daegu Gyeongbuk Institute of Science & Technology (DGIST), 50-1 Sang-Ri, Hyeonpung-Myeon, Dalseong-gun, Daegu 711-873, Republic of Korea article info Article history: Received 5 May 2013 Accepted 28 July 2013 Keywords: Diode parameters Concentrator solar cells Intensity of illumination Single diode model High illumination conditions abstract An analytical method has been developed to extract all four diode parameters, namely the shunt resis- tance, series resistance, diode ideality factor, and reverse saturation current density, using a single J–V curve, based on one exponential model of silicon solar cells under high illumination conditions. The slope of the J–V curve (dV/dJ) at a short circuit condition is used to determine the value of the shunt resistance. The slope of the J–V curve at an open circuit condition together with the short circuit current density, open circuit voltage, current density, and voltage at maximum power point have been used to determine the values of the series resistance, diode ideality factor, and reverse saturation current density. The deter- mined values of the diode parameters have been used to compute the theoretical values of the open cir- cuit voltage, curve factor, and efficiency of the solar cell. The theoretical J–V curves matched well with the corresponding experimental curves. This method is applied to determine the diode parameters of concen- trator silicon solar cells at different illumination conditions in a temperature range of 298–323 K. The computed values of the open circuit voltage, curve factor, and efficiency obtained using diode parameters determined with this method showed good agreement (<2% discrepancy) with the experimental values. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The J–V characteristics of a p-n junction silicon solar cell based on a single diode model under a steady state in the IVth quadrant are described by the following equation [1–20]. J ¼J ph þ J 0 e ðVJR s Þ nV T  1   þ ðV  JR s Þ R sh ð1Þ where V T = kT/q, J ph = light generated current density, q = electronic charge, k = Boltzmann’s constant, and T = operating temperature of the solar cell. There are several losses in the solar cells that affect the short circuit current density J sc , open circuit voltage V oc , curve factor CF, and efficiency g of the cells. The parameters J sc , V oc , CF, and g are referred as performance parameters of the solar cells [21]. The diode parameters (i.e. shunt resistance R sh , series resistance R s , diode ideality factor n, and reverse saturated current density J 0 ) control the J–V characteristics of a solar cell at any given inten- sity of illumination and operating temperature of the solar cells. The performance of as solar cell is monitored through the four performance parameters of the cell but the diode parameters dic- tate the values of the performance parameters at a given intensity of illumination and temperature. In fact, the diode parameters rep- resent the different types of loss mechanisms that affect the perfor- mance of solar cells. There are four diode parameters based on the single diode model, whereas there are six diode parameters based on the double diode model. The two additional diode parameters in the double diode model are due to recombination in the space charge region. Most often, however, under normal illumination conditions, a single diode model, with the four diode parameters, adequately describes the functioning of the solar cells because of negligible recombination in the space charge region [8,22,23]. A low value of R sh is due to a conductive path across the p-n junction and/or the edge of the solar cells. The R sh value can affect the V oc , CF, and g of the solar cells. A lower value of R sh indicates more shunting loss and gives lower values of V oc , CF, and g of the solar cells. R s is the sum of the resistances of the front and back metallic contacts, the contact resistances of the metallic contact with the front and back surfaces, and the resistance of the semi- conductor material. The value of n indicates the recombination in the bulk space charge regions and at the surfaces of the solar cells. A higher value of n gives a lower CF value. However, the J 0 value is also indicative of the recombination in bulk semiconductor materials and at the surfaces of solar cells. It decisively affects V oc of solar cells. A higher J 0 value results in a lower V oc value, and thereby a lower value of g. Determination of diode parameters has been studied by a num- ber of groups [6–20,24]. Generally, most of the suggested methods [7,17,18] determine the value of R sh by using the slope of the illu- 0196-8904/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.enconman.2013.07.054 ⇑ Corresponding author. Tel.: +82 53 7853610; fax: +82 53 7853439. E-mail address: jaehyun@dgist.ac.kr (J.H. Kim). Energy Conversion and Management 76 (2013) 421–429 Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman