IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 60, NO. 5, MAY 2011 1761 A Novel Measurement Method to Determine the C –V Characteristic of a Solar Photovoltaic Cell C. R. Jeevandoss, M. Kumaravel, Member, IEEE, and V. Jagadeesh Kumar, Member, IEEE Abstract—A novel method for characterizing a single crystalline or poly-silicon solar photovoltaic (SPV) cell is proposed. The extraction of the parameters of an SPV cell is hindered by the presence of its leakage resistance. It is demonstrated here that in employing a negative resistance, not only the C –V characteristics but also the R–V characteristics along with the built-in potential and the doping concentration of an SPV cell are easily ascertained. The experimental results presented herein validate the proffered method. Index Terms—Built-in potential, C –V characteristics, doping concentration, negative resistance, R–V characteristics, solar photovoltaic (SPV) cells. I. I NTRODUCTION O F THE AVAILABLE renewable energy sources, the growth rate of solar photovoltaic (SPV) systems is next only to that of the wind energy systems. Large solar arrays are being installed all over the world due to the declining cost of the SPV cells. In a typical SPV array, multiple SPV cells are connected in series as a module, and an array of modules is then connected through a power conditioner to the load. In order to optimally utilize the SPV system, the power conditioner must be designed and operated at an optimal level at all times. For the design and operation of SPV power condi- tioners, the parameters of the SPV module must be available. For example, to determine the optimum switching frequency of the power conditioner connected to an SPV module, the information on the value of the capacitance of the SPV cell as a function of its terminal voltage, which is popularly called as the capacitance–voltage (C–V ) characteristics, is essential [1], [2]. On the other hand, the determination of the doping concentration in a single crystalline or a poly-silicon SPV cell is important for identifying the optimal process that would lead to mass production of energy-efficient SPV cells. The doping concentration in semiconductor materials is determined with the aid of either a secondary iron mass spec- troscopy [3] or a Hall effect [4] or a C–V measurement [5]–[7] technique. The secondary iron mass spectroscopy provides the Manuscript received June 12, 2010; revised September 8, 2010; accepted October 5, 2010. Date of publication December 6, 2010; date of current version April 6, 2011. The Associate Editor coordinating the review process for this paper was Dr. Theodore Laopoulos. C. R. Jeevandoss and M. Kumaravel are with the Central Electronics Centre, Indian Institute of Technology Madras, Chennai 600 036, India (e-mail: jeevandoss@iitm.ac.in; mkum@iitm.ac.in). V. J. Kumar is with the Department of Electrical Engineering, Indian Institute of Technology Madras, Chennai 600 036, India. Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TIM.2010.2091183 chemical concentration of dopants in the silicon solar cell ma- terial but does not provide information on the electrically active doping concentration. Moreover, this method is a destructive test and hence can be conducted only on few representative samples [8]. The method based on Hall-effect measurements provides not only the active doping concentration but also the mobility of majority carriers. However, to make the Hall voltage measurements, a special test structure has to be employed. On the other hand, the C–V measurement technique is simple and provides active doping concentration without the need for any special test structure and also does not result in the destruction of the test sample. Once the C–V characteristic is obtained, the built-in potential of the SPV cell is easily extracted. Utilizing the measured C–V characteristics and the extracted built-in potential, the doping concentration of the SPV cell is determined. Due to its simplicity, this method can be used for in-line monitoring of the quality of the production process (diffusion process) itself. The capacitances present in a typical SPV cell are the following: 1) the diffusion capacitance C d and 2) the depletion capacitance C j . The single crystalline and poly-silicon SPV cells have single p-n junction with one side of the junction heavily doped than the other side, forming an abrupt junction. For an abrupt p-n junction under a reverse- bias condition, the overall capacitance is largely dictated by the depletion capacitance. The permittivity of silicon, the area of the PV cell, and the built-in potential and doping concentration determine the value of the depletion capacitance. A simplified equivalent circuit of an SPV cell, which is shown in Fig. 1, portrays all the capacitances of an SPV cell coupled together as a lumped equivalent capacitive element C P . The resistance R P , which is shown in the equivalent circuit in Fig. 1, once again includes the p-n junction resistance and the parasitic parallel resistance (arises due to the imperfection on the device surface; ≈ 1100 Ω/cm 2 for the single crystalline cell) as a lumped parallel resistor. It should be noted here that the values of C P and R P change with the magnitude and polarity of the voltage across terminals K and A of the SPV cell. This is due to the fact that a small change in voltage alters the width of the depletion region, resulting in a change in the charge density at the edges of the depletion region. This behavior is analogous to the case of classic parallel-plate capacitor with the distance between the plates varying, and thus, the capacitance C P will vary with the applied dc voltage. The parasitic parallel resistance also varies since it is dependent on the leakage current of the PV cell. The presence of the resistive component R P poses a challenge in measuring the capacitance C P as a function of the applied voltage. The effect of R P can be accounted, and C P can be determined if the impedance Z P 0018-9456/$26.00 © 2010 IEEE