Trans. Electr. Electron. Mater. 14(4) 177 (2013): D.-K. Kim et al.179Fig. 2. Experimental methods of alternating current(AC) voltagesource applying for the capacitance controlling of silicon p-n junctionsolar cell.Table 1. Alternating current(AC) voltage input parameter for controllingthe capacitance of the silicon solar cell.Fig. 3. The power conversion character result as a function of alternatingcurrent(AC) voltage input (The experiments 1).Division Input AC Voltage (V) Frequency (Hz)Experimental 1A phase : 0.1 VB phase : 0.1 VExperimental 2A phase : 0.2 VB phase : 0.2 VExperimental 3A phase : 0.3 VB phase : 0.3 VExperimental 4A phase : 0.4 V10, 20, 40,B phase : 0.4 V80, 160, 320Experimental 5A phase : 0.5 VB phase : 0.5 VExperimental 6A phase : 0.6 VB phase : 0.6 VExperimental 7A phase : 0.7 VB phase : 0.7 Vrectly effect. The power conversion was changed by alternatingcurrent(AC) voltage bias of 0.2~1.4 V and 6 frequency band characteristics,changed capacitance of depletion region could beobserved by the indirect method of direct current(DC) voltagecurrent.Such as the foregoing, discussion on the results of this paperwill be discussion about changing direct current(DC) voltagecurrentof electric field by changes capacitance in depletion region.The depletion region is defines a stationary state of donorand acceptor ion in the microscopic space-charge region.Such as results of this experiment, when analyzing of the powerconversion output characteristics of between the 6 frequencyband of 10~320 Hz, changed frequency per second shown tobe provide of direct cause in the charge density changes. In theexperiment results of each in Table 1, when input frequencyof 10 Hz, maximum current and minimum current show fluid,increasing of frequency, at 320 Hz, current measurement rangewas reduced. As confirmed from this phenomenon, capacitanceof the depletion region, because of changed frequency effect andit effect suggest of a directly cause in the charge movement.In addition, The charge can be easily moved along the alternatingcurrent(AC) voltage signal in the forward bias of lowfrequencies and it does not react easily by the high-frequencycondition .Additional studies of the capacitance which in the changes thebias state, the capacitance density by the positive and negativevoltage state showed conflicting results. From the results of thisstudy, as positive bias voltage increases, the capacitance densityshowed the increasing influence .On the other hand, in the measurement of open voltage of theFig. 4. The power conversion character result as a function of alternatingcurrent(AC) voltage input (The experiments 2).Fig. 5. The power conversion character result as a function of alternatingcurrent(AC) voltage input (The experiments 3).silicon solar cell could be observed of rapid changes. Essentially,in the characteristics of the diode, when applied in the reversedirection of alternating current(AC) voltage, which have rectificationcharacter and it show because of the gave to directly effectof charge distribution in the close-set charge of depletion region.In the analysis of equilibrium state, reverse bias stage, forwardbias state of the Silicon p-n junction diode, the most emphasisanalysis is changes of potential barrier. An applied of forwardand reverse bias gave a direct effect in the width change of deple-
180Trans. Electr. Electron. Mater. 14(4) 177 (2013): D.-K. Kim et al.Fig. 6. The power conversion character result as a function of alternatingcurrent(AC) voltage input (The experiments 4).Fig. 8. The power conversion character result as a function of alternatingcurrent(AC) voltage input (The experiments 6).Fig. 7. The power conversion character result as a function of alternatingcurrent(AC) voltage input (The experiments 5).Fig. 9. The power conversion character result as a function of alternatingcurrent(AC) voltage input (The experiments 7).tion region. An applied voltage in the externally has been knownto the transformative of electrostatic potential barrier. Becausephysical phenomenon, transformative to the charge density inthe transition region, several components of the current wasdemonstrated to changes .Thus, Hammond, P presented can be defined by equation -6which is the energy of the electric field.Q Q 2q 1 QW = ∫Vdq = ∫ dq =C 2 C0 01 2 1 2= CV = VQ2 2The occurrence source of this energy between the conductorsof capacitor is performed by outside influences.(optically absorptionand power apply) And In the p-n junction of depletionregion, because of the changed electric field is not relationshipcontinuous charge release by outside influences.In addition, When the electric field energy is permission movingequilibrium position, it is freedom is preserved. This energyis completed in the corroborated electric field . The changedelectric field by ionization carrier in the energy band, gave directeffect on the separation of generated electron-hole pairs due tosunlight absorption and it is directly related to the carrier diffusionand physical value of short current. Because of the characteristicsof applied alternating current(AC) voltage, changed(6)potential barrier shows of value of measured open voltage in the7 graphs of this paper. When observing the open voltage outputof a graph, minimum open voltage results showed a linear form.On the other hand, maximum open voltage showed very irregularand non-linear voltage characteristics results. In the depletionregion, Indigenous voltage (built-in voltage) can be appliedas follows. First, in the acceptor area, indigenous voltage can bedefined as equation -7.xp→xpkT 1 dp0Vbi= ∫ E dx = ∫ dxq pxnxn 0dx−−p0( xp)kT0kT ⎡0dp p ( xp)⎤= lnq∫ = ⎢ ⎥p0 q ⎣p0( −xn)⎦p0( − xn)In succession, indigenous voltage of the donor area can be definedas equation (-8)−xn→−xnkT 10Vbi= ∫ E dx = ∫ dxq nxpxp 0dxn0( − xn)kT0kT ⎡0dn n ( −xn)⎤= lnq∫ = ⎢ ⎥n0 q ⎣ n0( xp)⎦n0( xp)dnWhen external voltage is applied such as this experiment, indigenousvoltage change can be deployed as equation-9.(7)(8)
Trans. Electr. Electron. Mater. 14(4) 177 (2013): D.-K. Kim et al.1812ε ⎛ Na+ N ⎞dWD ( V) = xn + xp = ⎜ ⎟( Vbi−V)q⎝NNa d ⎠In this equation, because effect of ionization carrier is generatedto inside electric field and the internal electric field provideof carrier separated of electron-hole pair. The V applying of externalvoltage show directly effect on the inside potential differencedecreases.Because of the applied effect of alternating current(AC) voltagein the depletion region of the silicon p-n junction, by changedfrequency effect of every second unit could be an indirect confirmationto changing a potential difference.Also, current output such as movement of carrier diffusioncould be confirmed by indirectly method of physical interruptionfactor by locally. The potential difference between twojunctions in the depletion region, when the charge density ofacceptor and donor ion is always constant which voltage outputis constant output. However, the open voltage of solar cell in thisexperiment showed always irregular measured result. The opticallyabsorption of electromagnetic radiation to a silicon crystallattice caused the photoelectric effect of the ground state carrier.The bias input in both ends of the silicon p-n junction semiconductoris basically generate of carrier drift current and diffusioncarrier which is obtained for the energy of the electric field andcarrier movement can think to the acceleration. The characterof the alternating current(AC) voltage is change to phase of everysecond cycle. therefor, In the depletion region of solar cellis temporally generated of the forward bias and reverse bias.Accordingly, the capacitance of the depletion region is affected.When applied alternating current(AC) voltage to the solar cellis saturation state, carrier movement not formed to any more.When saturation state of the applied alternating current(AC)voltage of solar cell is not any more formed to carrier movement.The saturation state of alternating current(AC) voltage is definedhigher applied than generated voltage difference by silicon p-njunction. When the experiments to higher voltage than maximumvoltage 1.4 V was temporarily inoperative to square wavegeneration equipment.The excessive alternating current(AC) voltage is applied in thesilicon solar cell, capacitance effect of depletion region is definedto the effect to completely lost. The disable operation stateof square wave generation equipment is defined to inability ofinsulators function as capacitance charge of large number concentratedof silicon p-n junction.Typically, in the depletion region of silicon p-n junction is definedto the breakdown as physical effects. Because of the influenceto alternating current(AC) voltage with a square wave pulseis decreasing of excess carrier separate. And in the movementof carrier diffusion did not get enough acceleration force whichpower conversion process can be analysis as affected.(9)5. CONCLUSIONSSo far, as described qualitatively in the results for this experiment,understanding for internal structure of capacitor usingpassive element in the R.L.C circuit was analyzed for power conversionwith changed capacitance.Using a square wave of 10~320 Hz frequency and an alternatingcurrent(AC) voltage source of 0.2~1.4 V, in the depletionregion of the silicon p-n junction solar cell was analyzed to thecharacter of power conversion of silicon solar cell. In the mastercourse thesis theme of the author’s with solar cell research ofcompound semiconductor for high efficiency power conversion was performed to the experiment by extending to uncompletedportion. Mainly, in the depletion region of the hetero-junction,charge density and changed electric field were analyzed toquantitative calculation and capacitance term of diode depletionregion has not exact mention.Therefore, in this paper, along with the changes of charge densitywhich is directly related to the power conversion efficiency,and directly controlled by the capacitance of the depletion region,power conversion of silicon solar cell could be analyzed assuch this results.REFERENCES K. A. Tsokos, “Physics for the IB Diploma”, Fifth edition, CambridgeUniversity Press, Cambridge (2008). Jun-Sin Lee, Kyeong-Hae Kim, Engineering of Solar Cell, pp.324 (Green Publishing, Korea, 2007). Mauk P, Tavakolian H, Sites J, IEEE trans, Electron Dev, 37,1065-1068 (1990) [DOI: http://dx.doi.org/10.1109/16.46377]. Kyeong-nam Jeon, Seon-hun Kim, Hoy-jin Kim, In-sung Kim,Sang-hyun Kim, A Study of the Quantitative Relationship ofCharge Density Changes and the Design Area of a FabricatedSolar Cell, TEEM Vol. 12, No. 5 (2011). Streetman, Bem G., Banergee, Sanjay Kumar, Solid Stage ElectronicDevices, Prentice Hall, pp. 202-203 (2005). R. SALACH-BIELECKI*, T. STAPIKI, and P. WCIK, Influece ofjunction parameters on the open circuit voltage decay in solarcells. OPTO-ELECTRONICS REVIEW 12(1) 79-83 (2004). Pyung-ho Choi, Hyo-jung Kim, Do-hyun Baek, Byung-deogChoi., A Study on the Electrical Characteristic Analysis of c-SiSolar Cell Diodes, JSTS Vol. 12, No. 1, March (2012). Hammond, P, Electromagnetism for Engineers, pp 44-45, PergamonPress (1965). In-sung Kim, A study of optimization of P-Al x Ga 1-x As/GaAs Solarcell process technology for high efficiency power conversion,Gwang ju University (2009).