IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 60, NO. 5, MAY 2011 1761

A Novel Measurement Method to Determine theC–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 crystallineor poly-silicon solar photovoltaic (SPV) cell is proposed. Theextraction of the parameters of an SPV cell is hindered by thepresence of its leakage resistance. It is demonstrated here that inemploying a negative resistance, not only the C–V characteristicsbut also the R–V characteristics along with the built-in potentialand the doping concentration of an SPV cell are easily ascertained.The experimental results presented herein validate the profferedmethod.

Index Terms—Built-in potential, C–V characteristics, dopingconcentration, negative resistance, R–V characteristics, solarphotovoltaic (SPV) cells.

I. INTRODUCTION

O F THE AVAILABLE renewable energy sources, thegrowth rate of solar photovoltaic (SPV) systems is next

only to that of the wind energy systems. Large solar arraysare being installed all over the world due to the decliningcost of the SPV cells. In a typical SPV array, multiple SPVcells are connected in series as a module, and an array ofmodules is then connected through a power conditioner to theload. In order to optimally utilize the SPV system, the powerconditioner must be designed and operated at an optimal levelat 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 frequencyof the power conditioner connected to an SPV module, theinformation on the value of the capacitance of the SPV cellas a function of its terminal voltage, which is popularly calledas the capacitance–voltage (C–V ) characteristics, is essential[1], [2]. On the other hand, the determination of the dopingconcentration in a single crystalline or a poly-silicon SPV cellis important for identifying the optimal process that would leadto mass production of energy-efficient SPV cells.

The doping concentration in semiconductor materials isdetermined 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; acceptedOctober 5, 2010. Date of publication December 6, 2010; date of current versionApril 6, 2011. The Associate Editor coordinating the review process for thispaper was Dr. Theodore Laopoulos.

C. R. Jeevandoss and M. Kumaravel are with the Central ElectronicsCentre, 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 Instituteof Technology Madras, Chennai 600 036, India.

Color versions of one or more of the figures in this paper are available onlineat 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 activedoping concentration. Moreover, this method is a destructivetest and hence can be conducted only on few representativesamples [8]. The method based on Hall-effect measurementsprovides not only the active doping concentration but also themobility of majority carriers. However, to make the Hall voltagemeasurements, a special test structure has to be employed. Onthe other hand, the C–V measurement technique is simpleand provides active doping concentration without the needfor any special test structure and also does not result in thedestruction of the test sample. Once the C–V characteristicis obtained, the built-in potential of the SPV cell is easilyextracted. Utilizing the measured C–V characteristics and theextracted built-in potential, the doping concentration of the SPVcell is determined. Due to its simplicity, this method can beused for in-line monitoring of the quality of the productionprocess (diffusion process) itself. The capacitances present in atypical SPV cell are the following: 1) the diffusion capacitanceCd and 2) the depletion capacitance Cj . The single crystallineand poly-silicon SPV cells have single p-n junction with oneside of the junction heavily doped than the other side, formingan abrupt junction. For an abrupt p-n junction under a reverse-bias condition, the overall capacitance is largely dictated by thedepletion capacitance. The permittivity of silicon, the area ofthe PV cell, and the built-in potential and doping concentrationdetermine the value of the depletion capacitance.

A simplified equivalent circuit of an SPV cell, which isshown in Fig. 1, portrays all the capacitances of an SPV cellcoupled together as a lumped equivalent capacitive element CP .The resistance RP , which is shown in the equivalent circuitin Fig. 1, once again includes the p-n junction resistance andthe parasitic parallel resistance (arises due to the imperfectionon the device surface; ≈1100 Ω/cm2 for the single crystallinecell) as a lumped parallel resistor. It should be noted here thatthe values of CP and RP change with the magnitude andpolarity of the voltage across terminals K and A of the SPVcell. This is due to the fact that a small change in voltagealters the width of the depletion region, resulting in a changein the charge density at the edges of the depletion region.This behavior is analogous to the case of classic parallel-platecapacitor with the distance between the plates varying, and thus,the capacitance CP will vary with the applied dc voltage. Theparasitic parallel resistance also varies since it is dependent onthe leakage current of the PV cell. The presence of the resistivecomponent RP poses a challenge in measuring the capacitanceCP as a function of the applied voltage. The effect of RP canbe accounted, and CP can be determined if the impedance ZP

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1762 IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 60, NO. 5, MAY 2011

Fig. 1. Simplified equivalent circuit of an SPV cell. CP is the equivalentcapacitance, and RP is the leakage resistance.

(which is equal to the parallel combination of CP and RP ) isdetermined. Of the several methods proposed earlier to obtainthe C–V characteristics of semiconductor devices, only a fewdeal with SPV cells [5]–[7]. In the methods proposed earlier,the necessary dc reverse-bias voltage is applied to the solar cell,and the impedance ZP is determined by superimposing a smallac sinusoidal voltage on the dc, and the ZP is determined atthat frequency. While this technique is best suited for SPV cellspossessing very low leakage current, it is not suitable for largearea SPV cells, particularly poly-silicon SPV cells that possesslow shunt resistance.

A method of determination of the C–V characteristics, uti-lizing negative resistance to compensate the leakage resistanceof an SPV cell was presented earlier [9]. Herein, the method isfurther refined so as to obtain optimal compensation. Moreover,it is shown that the proposed method, apart from providingthe C–V and R–V characteristics, enables the computation ofthe built-in potential and, more importantly, the active dopingconcentration. The analysis of the proposed method for possibleerrors in the measurement is also presented here.

II. MEASUREMENT OF THE SPV CELL CHARACTERISTICS

A. Nulling the Effect of RP

In the proffered method, a negative resistance Rx is con-nected across the terminals K and A of the SPV cell, asshown in Fig. 2(a). The parallel combination of the SPV celland the negative resistance is excited by a suitable dc voltageof the magnitude VB in series with an ac current source, asindicated in Fig. 3(a). It is easily shown in Fig. 2(a) that theeffect of RP can be nulled if Rx = RP . Once this conditionis met, then across the terminals K and A, only the parallelequivalent capacitance CP exists, as indicated in Fig. 2(b).Any measurement taken across the terminals K and A in thissituation will now be only due to CP .

B. Method of Measurement of CP

The output of the current source (a symmetrical square-wavecurrent of magnitude ± IS A and having a period TS) andthe resulting voltage vc across the terminals K and A of thecompensated SPV cell are shown in Fig. 3(b). In Fig. 3(b), thepeak-to-peak voltage 2 VP can be obtained as

2VP =1

CP

Ts/2∫0

iSdt = ISTS

2CP. (1)

Fig. 2. Compensation of the parallel resistance RP of an SPV cell with anegative resistance RP .

Fig. 3. (a) Scheme for obtaining the C–V characteristic of an SPV cell(compensated with a parallel negative resistance RP , as shown in Fig. 2).(b) Waveforms of the source current iS and the capacitance voltage vc.

Rearranging (1), we get the following:

CP =TSIS

4VP. (2)

Utilizing the values of TS , IS , and VP , the equivalent parallelcapacitance can be computed with the help of (2). The C–Vcharacteristic at a particular excitation frequency (fS = 1/TS)is obtained by determining the CP for different values of VB

while maintaining TS constant. Similarly, the variation of CP

as a function of frequency can be obtained by varying TS whilemaintaining VB constant. Thus, a family of C–V or C − fcharacteristics is easily obtained. In order to ensure that CP

remains constant during a measurement, the magnitude of VP

must be kept small by adjusting the value of IS .

C. Extraction of the Built-in Potentialand the Doping Concentration

Under a reverse-bias condition, the capacitance CP of anabrupt p-n junction SPV cell is largely due to the depletioncapacitance Cj arising out of charge stored in the depletionlayer [10] and can be expressed as

CP ≈ Cj = A

√qεoεrNBAC

2(VF + VB)(3)

where q is the charge of the electron, εo is the permittivityof free space, εr is the relative dielectric constant of silicon,

JEEVANDOSS et al.: NOVEL MEASUREMENT METHOD TO DETERMINE THE C–V CHARACTERISTIC OF AN SPV 1763

NB = NAND/(NA + ND) with NA being the doping concen-tration in P region, whereas ND is that of the N region, and AC

is the area of the SPV cell. From (3), the built-in potential VF

is obtained as [10]

VF = VT ln[(NA ND)/N2

i

]. (4)

Here, Ni is the intrinsic concentration for the semiconductormaterial and VT = kT/q, k being the Boltzmann constant, andT is the temperature in kelvin. Rearranging (3), we obtain thefollowing:

1C2

j

=2

qεoεrNBA2C

(VF + VB). (5)

Equation (5) indicates that the plot of 1/C2j as a function of

VB will result in a straight line with a slope m and a y-interceptVF . The value of m can be obtained as

m =d(1/C2

j )dVB

=2

qεoεrNBA2C

. (6)

Thus, after obtaining the required C–V characteristic, 1/C2j

as a function of VB is plotted. From the plot, the slope mand the y-intercept are extracted. The y-intercept is the built-in potential and the doping concentration is computed using (6)and the extracted slope m.

D. Measurement of the Parallel Resistance RP

Once the leakage resistance is compensated, then Rx = RP .Hence, by using a calibrated resistance for Rx, RP is easilydetermined. Thus, using the proposed method, not only theC–V characteristic but also the R–V characteristic of the SPVcell under test is obtained. The experimental validation of theproposed method is given next, and the possible sources oferrors are analyzed in the sequel.

III. EXPERIMENTAL VALIDATION

Implementing the scheme portrayed in Fig. 3(a) in a practicalsense results in a paradoxical situation. To compensate theeffect of RP , the value of the negative resistance Rx must beset exactly equal to RP , but RP is unknown. Moreover, thevalue of RP changes with the applied bias voltage. To overcomethis problem, the scheme shown in Fig. 3(a) is implementedpractically with a small but significant variation, as shown inFig. 4. The current source iS in Fig. 3(a) is replaced with avoltage source vS in series with a fixed standard resistance RS .The opamp OA along with the resistors RI is configured as anegative impedance converter and realizes an impedance acrossnodes K and A, which is equal in magnitude but opposite inpolarity of the impedance that exists between nodes K and C.Between nodes K and C, a variable resistance Rx in parallelwith a series combination of RF and C1 is connected. Thevalue of RF is chosen to be equal to RS . It is easily seen thatVB is a dc voltage, and vS is a square-wave ac, whereas vC ,i.e., the voltage at node K, contains dc VC and square-wave acv∼

C components. Similarly, vo, i.e., the output of opamp OA, is

also made of dc Vo and square-wave ac v∼o components. Hence,

the current iP through the leakage resistance RP also containsdc IP and square-wave ac i∼P components. To ensure propercancellation of the effect of RP , the following criteria mustbe met:

Ix = IP , i∼x = i∼P , and i∼f =v∼

C

RS.

Here, i∼f is the square-wave current flowing through RF , Ix

is the dc current, and i∼x is the square-wave current flowingthrough Rx. Writing KCL for the dc components of currentsmeeting at node K, we get the following:

VB − VC

RS+

Vo − VC

Rx− VC

RP− IC = 0. (7)

With vo = 2vC and adjusting Rx such that Rx = RP ensuresthat the dc current IC through CP is zero, and hence

VC = VB. (8)

Equation (8) indicates the dc voltage between nodes K andB, namely, VKB = 0. Under this condition, applying KCL forthe ac component of the currents at node K (assuming the valueof C1 to be very large) results in the following:

vS − v∼C

RS+

v∼o − v∼

C

Rx+

v∼o − v∼

C

RF− v∼

C

RP− i∼C = 0. (9)

With RF = RS , we get

i∼C =vS

RS. (10)

Thus, if Rx is varied until the dc voltage across terminalsK and B is zero, then the current iC through the capacitor CP

is only the pulse current vS/RS . Thus, the criterion “vary Rx

until the dc voltage across terminals K and B is zero” ensuresthat the effect of RP is compensated without actually knowingthe value of RP .

Thus, to obtain the value of CP at a particular bias conditionVB , the value of VB is set on the variable dc bias voltage source,as shown in Fig. 4. The value of Rx is then adjusted such thatthe dc voltage across the terminals K and B is zero. Underthis condition, the peak value VP of the triangular voltageappearing across the terminals K and A is measured. CP iscomputed using (2) with the set values of TS , IS (= VS/RS ,VS being the peak value of the square-wave voltage vS), and themeasured value VP . This process is repeated for different valuesof VB , and the C–V characteristic spanning over the range ofbias voltage of interest is plotted. An added advantage of theproposed implementation is under a compensated condition;Rx is equal to RP ; thus, the unknown RP is also ascertained.

A prototype unit based on the proposed method was built us-ing commercially available components and was tested. OpampOA, which is shown in Fig. 4, was realized by cascading an AD547 opamp and an L272 power opamp. The AD 547 was specif-ically chosen as it possesses an input equivalent capacitance of< 3 pF. Since the opamp OA has to supply adequate powerto energize the resistances (values in the range of few tens ofohms to few hundred ohms), the power stage L272, which can

1764 IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 60, NO. 5, MAY 2011

Fig. 4. Experimental setup for measuring the C–V characteristics of an SPVcell using a negative resistance compensation.

deliver a maximum output current of 0.6 A, is essential. AnHP 33120A function generator served as the voltage source vS .The amplitude of Vs is chosen as 5 V, and the value of RS isset as 10 kΩ. The value of the capacitor C1 is determined byω1C1RS > 20 so as to make the error introduced by C1 to benegligible in the frequency range of interest. Here, ω1 is thefundamental frequency of the square-wave excitation, and C1 ischosen as 10 μF. The value of R1 is 10 kΩ. Rx is realized witha laboratory standard variable resistance of accuracy class 0.01.The output was observed on an Agilent 54621A oscilloscope,and measurements were made using a Keithley 2000 6 1/2 digitmultimeter. The output triangular wave is found to be linear,particularly when the condition for compensating the parallelresistance is met.

In order to evaluate the practicality of the proposed tech-nique, a calibrated standard capacitor of value 1.0 μF, withnegligible leakage resistance, was used with different knownvalues of resistances connected in parallel to emulate differentvalues of RP . The value of 1.0 μF was chosen to mimic thepractical capacitance of a typical solar cell. The resistance rangeof RP is set as 40 to 200 Ω, once again, to be within the rangeof the practical values of a typical SPV cell. The capacitancevalue is then determined for various values of RP , employingthe proposed method. The results portrayed in Table I validatethe technique presented here. In spite of the presence of the par-allel resistance, the CP value is determined within acceptablelevel of accuracy. Utilizing the proposed technique, the C–Vcharacteristics of single crystalline and poly-silicon SPV cellsof dimensions 10 cm by 10 cm and 4 cm by 2.5 cm, respectively,are determined.

Fig. 5 portrays the C–V characteristic of single crystallinesilicon SPV cell determined using the proposed method andcompared with the one obtained through the traditional im-pedance method. The results from the proposed method arein agreement with the standard method. While the standard

method requires sophisticated and expensive impedance ana-lyzer, the proposed method is simple and requires only “off-the-shelf” instrumentation. Fig. 6 shows the C–V characteristic ofa typical poly-silicon SPV cell. Fig. 7 portrays the variation ofRP obtained for different bias voltages for a single crystallineand a poly-silicon SPV cell. It is shown that the per-unit-leakage resistance of a poly-silicon SPV cell is about an orderof magnitude smaller than that of the single crystalline siliconSPV cell.

In Fig. 6, the value 1/C2P is computed and plotted along

with CP . As expected, the 1/C2P plot results in a straight line,

validating (5). As explained earlier, the y-intercept of the 1/C2P

line provides the built-in potential (0.75 V). From the slopem of the 1/C2

P straight line, the doping concentration NB isobtained by using (6) and found to be 1.345 × 1016 cm−3. Thisvalue matches with the data provided by the manufacturer. Theexperimental results, as shown earlier, validate the proposedtechnique. Possible sources of errors in the proposed techniqueare analyzed next.

IV. SOURCES OF ERRORS IN THE PROPOSED METHOD

In deriving (2), (8), and (10), the components and devicesemployed are assumed to be ideal. However, practical com-ponents and devices will possess nonideal behavior, and thenonidealities will introduce errors in the measurement. Thefollowing sections quantify such errors.

A. Influence of Series Resistance RC

While deriving the equivalent circuit in Fig. 1, the effect ofcontact resistances (contacts of front and back surfaces andthe n+ diffused layer) were assumed to be negligible. Fig. 8portrays a more comprehensive equivalent circuit of an SPVcell that includes RC , i.e., the equivalent series resistance thatrepresents the effect of the resistances of all contacts. Under areverse-bias condition, this resistance will be very small (in theorder of a few hundred milliohms) compared with the parallelresistance RP , which will be in the order of a few hundredohms. Hence, the error introduced by the series resistance onthe measurements taken with the SPV cell in reverse bias isvery small (< 0.1%). Since the time constant RCCP will be inthe order of 10−7, the errors introduced in the measurement ofCP will also be negligible.

However, under a forward-bias condition, RP is in the orderof a few ohms. Hence, the presence of RC will produce largeerrors if the effect of RC is not considered. In the proposedmethod, the dc current through the SPV cell is ensured to bezero while making a measurement, and hence, both RC andRP are compensated. Thus, the error on the measurement ofCP will be negligible. However, the measurement of RP willbe in error in the forward-bias condition as the measured valuewill be (RP + RC) and not RP .

B. Effect of Stray Capacitances

Stray capacitances 1) from either node (K or A) to groundand 2) between terminals K and A will be present. The terminal

JEEVANDOSS et al.: NOVEL MEASUREMENT METHOD TO DETERMINE THE C–V CHARACTERISTIC OF AN SPV 1765

TABLE IEXPERIMENTAL RESULTS (CP = 1.0 μF)

Fig. 5. C–V characteristic of a single crystal silicon SPV cell (10 cm by 10 cm) obtained by the proposed method and compared with that through the impedancemeasurement method.

Fig. 6. C–V characteristics of a poly-silicon SPV cell obtained by theproposed method. 1/C2

P is plotted, and through linear regression, the built-inpotential VF is obtained.

A is grounded, and hence, all the stray capacitances will comein parallel to CP . Since the value of CP is in the order ofmicrofarads, and the stray capacitances will be a few tens ofpicofarads, the error introduced in the measurement of CP

due to the presence of stray capacitances will be negligible(< 0.1%).

C. Error Due to Mismatch in the Resistances

If the effect of RP is not fully compensated with −Rx, andthe portion of RP that is not compensated is ΔRP , then, thecapacitor voltage and current will be the following:

VC =VB

(1 − RS

RS + ΔRP

)and (11)

iC =vS

Rs

(1 − vCRS

vSΔRP

). (12)

Both the bias voltage applied to CP and the value of thecurrent employed in computing CP will be in error. The errorεΔRP

in the computation of CP due to deficiency in compen-sating RP fully is as follows:

εΔRP= − VP RS

VSΔRP100%. (13)

Here, the error due to RS is not considered as it is assumedthat a standard resistor with high accuracy is employed for RS .Similarly, the error due to the mismatch that can arise betweenRS and RF is not considered as this error can be easily kept toa minimum by choosing matched resistances of equal value forRS and RF .

1766 IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 60, NO. 5, MAY 2011

Fig. 7. Resistance per unit area of the single crystal and poly-silicon SPV cells obtained using the proposed method.

Fig. 8. Modified equivalent circuit of an SPV cell (including the contactresistance).

Apart from the aforementioned error, if RP is not com-pensated, the voltage across the capacitor CP will no longerbe linear, as indicated in Fig. 3(b), but will be exponentiallyincreasing and decreasing. Then, the peak voltage reached atthe end of TS/2 will not be VP but V ′

P and V ′P < VP . An error

in the measurement of CP due to the uncompensated RP willarise only due to the error in VP , which is easily shown in (2).Under the uncompensated condition, it can be deduced that

V ′P = RP IS

(1 − e−TS/RP CP

1 + e−TS/RP CP

).

Resulting in an error in the measurement of CP due to theuncompensated RP as

εRP=

(1 − 4RP CP

TStanh

(TS

4RP CP

))100%. (14)

D. Error due to Opamp Bias Current and Offset Voltage

The opamp with bias currents I+ and I− at the noninvertingand inverting terminals, respectively, along with its input offsetvoltage ΔV , will introduce errors only in the dc bias voltageof the capacitor. The bias current I− at the inverting terminalof the opamp will not influence the capacitor voltage. The biascurrent I+ at the noninverting terminal of the opamp also willnot influence the capacitor voltage as the capacitor voltage isenforced by the bias source VB under balanced (VKB = 0)condition. However, it is prudent to choose an opamp with

ultralow bias current as the opamp OA in Fig. 4 and alsoimplement offset nulling.

E. Error due to Finite Value of the Capacitance C1

With a finite value for the capacitor C1, which is under a nullcondition (VKB = 0), the current through capacitor CP will beas follows:

iC ≈ vS

RS− vC

RS+

vC

RS

(1 +

1ω2

1R2SC2

1

)− 12

.

Expanding (1 + (1/ω21R2

SC21 ))−(1/2) into power series, as-

suming (ω21R2

SC21 ) � 1 and neglecting higher order terms, we

get the following:

iC ≈ vS

RS

(1 − vC

2vSω21R2

SC21

). (15)

Substituting peak values of vS and vC in (15) results in anerror εC1 in the measured values of CP due to the finite valueof C1 as

εC1 = −(

VP

2VSω21R2

SC21

)100%. (16)

Once these constraints are addressed, then, the accuracy ofthe capacitance measurement largely depends on the accuracywith which VS , VP , and TS are measured, as given next.

F. Error due to Measurement Errors in TS , VS , and VP

Overall, the measurement error (systematic) εCPin the mea-

surement of CP is calculated by differentiating (2) and substi-tuting the respective errors εTS

, εVS, and εvP

in measuring TS ,VS , and VP as

εCP= εTS

+ εVS+ εvP

. (17)

It should be noted here that although the error analysis isaccomplished considering the individual constraints, one at atime, the overall error will be a combination of all the errors.

JEEVANDOSS et al.: NOVEL MEASUREMENT METHOD TO DETERMINE THE C–V CHARACTERISTIC OF AN SPV 1767

V. CONCLUSION

To optimally utilize a silicon SPV cell, knowledge of itsC–V and C–F characteristics and built-in potential is nec-essary. Additionally, to control the quality of the diffusionprocess during manufacturing stage, information on activedoping concentration is needed. The presence of appreciableleakage resistance makes it difficult to directly obtain the C–Vor C − f characteristics of the SPV cells. A novel method ofmeasurement of the C–V and C − f characteristics of the SPVcells employing a negative resistance to null the effect of theleakage resistance has been proposed here. Over and abovefacilitating the measurement of C–V and C − f characteristics,the proffered method has provided a measure on the variationof the leakage resistance, the doping concentration, and thebuilt-in potential of the SPV cell under the test. The proposedmethod has been validated through the results obtained throughthe experimentation that has been conducted on a prototypeunit that has been built and tested. The error analysis that hasbeen presented herein brings out the constraints on the choiceof various parameters, including the accuracy required in themeasuring instruments employed in the test setup.

REFERENCES

[1] A. Carrigos, J. M. Blanes, J. A. Carrasco, and J. B. Ejea, “Influence of theparasitic solar array capacitance to the sequential switching shunt seriesregulator,” in Proc. IEEE Mediterranean Electro Tech. Conf., Malaga,Spain, May 16–19, 2006, pp. 1196–1201.

[2] Anilkumar, M. S. Suresh, and J. Nagaraju, “Effect of solar array capac-itance on the performance of switching shunt voltage regulator,” IEEETrans. Power Electron., vol. 21, no. 2, pp. 543–548, Mar. 2006.

[3] C. Agashe, O. Kluth, J. Hupkes, U. Zastrow, B. Rech, and M. Wuttig, “Ef-forts to improve carrier mobility in radio frequency sputtered aluminumdoped zinc oxide films,” J. Appl. Phys., vol. 95, no. 4, pp. 1911–1917,Feb. 2004.

[4] C. W. Farely and B. G. Streetman, “The Schottky-gated hall-effect tran-sistor and its application to carrier concentration and mobility profilingin GaAs MESFETs,” IEEE Trans. Electron Devices, vol. ED-34, no. 8,pp. 1781–1787, Aug. 1987.

[5] F. Recart and A. Cuevas, “Application of junction capacitance mea-surements to the characterization of solar cells,” IEEE Trans. ElectronDevices, vol. 53, no. 3, pp. 442–448, Mar. 2006.

[6] P. H. Mauk, H. Tarakolian, and J. R. Sites, “Interpretation of thin-filmpolycrystalline solar cell capacitance,” IEEE Trans. Electron Devices,vol. 37, no. 2, pp. 422–427, Feb. 1990.

[7] R. Anilkumar, M. S. Suresh, and J. Nagaraju, “Measurement of ACparameters of gallium arsenide (GaAs/Ge) solar cell by impedance spec-troscopy,” IEEE Trans. Electron Devices, vol. 48, no. 9, pp. 2177–2179,Sep. 2001.

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[9] C. R. Jeevandoss, M. Kumaravel, and V. J. Kumar, “A novel method forthe measurement of the C–V characteristic of a solar photovoltaic cell,”in Proc. IEEE I2MTC, Austin, TX, May 3–6, 2010, pp. 371–374.

[10] S. M. Sze, Physics of Semiconductor Devices. New York: Wiley, 1969.

C. R. Jeevandoss was born in Chennai, India, onMarch 1, 1968. He received the B.S. degree inelectronics and communication engineering from theInstitution of Engineers, Kolkatta, India, in 1992 andthe M.Tech. degree in electrical engineering from theIndian Institute of Technology Madras (IIT Madras),Chennai, in 2000, where he is currently working to-ward the Ph.D. degree in the area of instrumentationand measurements.

He has been with the Central Electronics Centre,IIT Madras, for the past 23 years and is currently

employed as an Instrumentation Engineer. His research interests are in the areasof measurements, instrumentation, and solar photovoltaics.

M. Kumaravel (M’05) was born in Tamil Nadu,India, on November 10, 1948. He received the B.S.degree in electronics and communication engineer-ing from the Institution of Engineers, Kolkatta, India,in 1972, the M.S. degree in applied electronics engi-neering from the Anna University, Chennai, India, in1981, and the Ph.D. degree from the Indian Instituteof Technology Madras (IIT Madras), Chennai,in 1994.

Since 1971, he has been with the IIT Madras, andhe is currently the Chief Design Engineer and the

Head with the Central Electronics Centre, IIT Madras. He has traveled widelyand visited several universities, industrial establishments, and photovoltaicindustries in Germany, USA, Japan, China, Malaysia, and Sri Lanka. He haspublished more than 15 research papers in journals and presented more than50 papers in international conferences. His research interests are in the areasof industrial electronics, electronic measurements, biomedical instrumentation,and solar photovoltaics.

V. Jagadeesh Kumar (M’96) was born in Madras,India, on July 21, 1956. He received the B.E. degreein electronics and telecommunication engineeringfrom the University of Madras, Chennai, India, in1978 and the M.Tech. and Ph.D. degrees in electricalengineering from the Indian Institute of TechnologyMadras (IIT Madras), Chennai, in 1980 and 1986,respectively.

He was a “Better Opportunities for Young Sci-entists in Chosen Areas of Science & Technology”Fellow at the King’s College, London, U.K., from

1987 to 1988 and a Deutscher Akademischer Austausch Dienst Fellow at theTechnical University of Braunschweig, Braunschweig, Germany, in 1997. Heworked as a Visiting Scientist with the Technical University of Aachen, Aachen,Germany, in 1999. He taught for a term at the Asian Institute of Technology,Bangkok, Thailand, in the summer of 1999. He is currently a Professor withthe Department of Electrical Engineering, IIT Madras. He is the holder ofsix patents and has published more than 40 papers in international journalsand presented more than 60 papers at various conferences. His teaching andresearch interests are in the areas of measurements, instrumentation, and signalprocessing.