太阳光 表面电极 减反射膜 1 背电极 Vm Voc pn结 Fig.7 Solar cell's V-A characteristics equivalent circuit of solar cell Figure 6 Structure of the crystalline silicon solar cells 2)Characterazation parameters of the solar cell Similar to the photocell,the current in solar cell,short circuit current and open-circuit voltage are described by equation(1),(2)and (3).If we ignore the series resistance Rs in the solar cell,V is the solar cell terminal voltage. When the solar cell is connected to a load R,I-V curve with the load is shown in Figure 2. Load R can vary from zero to infinity.The output power has a maximum at same value of load. The maximum output power of the solar cell is: P=IV (7) Im and Vm are the optimal current and best operating voltage,respectively.Define the ratio of the product of Voe and Ise and maximum power Pm as the filling factor FF: FF=P。-'l (8) Voels Voel FF is an important characterization parameter of the solar cell,the greater FF the higher the output power.FF depends on the incident light intensity,the band gap of the material,the ideal coefficient,series resistance and parallel resistance,etc. The solar cell conversion efficiency n is defined as the ratio of the maximum output power Pm and the total radiation power on the solar cells Pin. 7= .×100% (9) 3)Equivalent circuit of solar cell The equivalent circuit of a solar cell is shown in figure 8,consisting of PN junction diode,constant current source Iph,the series resistance Rs such as contact resistance, equivalent parallel resistance Rh that is related to the leakage current in PN junction.The output current and voltage of a solar cell is: .6-- 6 - 太阳光 减反射膜 表面电极 背电极 pn 结 p n Figure 6 Structure of the crystalline silicon solar cells 2) Characterazation parameters of the solar cell Similar to the photocell, the current in solar cell, short circuit current and open-circuit voltage are described by equation (1), (2) and (3). If we ignore the series resistance Rs in the solar cell, V is the solar cell terminal voltage. When the solar cell is connected to a load R, I - V curve with the load is shown in Figure 2. Load R can vary from zero to infinity. The output power has a maximum at same value of load. The maximum output power of the solar cell is: m mVm P = I （7） Im and Vm are the optimal current and best operating voltage, respectively. Define the ratio of the product of Voc and Isc and maximum power Pm as the filling factor FF: oc sc m m oc sc m V I V I V I P FF = = (8) FF is an important characterization parameter of the solar cell, the greater FF the higher the output power. FF depends on the incident light intensity, the band gap of the material, the ideal coefficient, series resistance and parallel resistance, etc. The solar cell conversion efficiency η is defined as the ratio of the maximum output power Pm and the total radiation power on the solar cells Pin. = ×100% in m P P η （9） 3) Equivalent circuit of solar cell The equivalent circuit of a solar cell is shown in figure 8, consisting of PN junction diode, constant current source Iph, the series resistance Rs such as contact resistance, equivalent parallel resistance Rsh that is related to the leakage current in PN junction. The output current and voltage of a solar cell is : Vm Voc Im Isc I V Rm 1 Fig.7 Solar cell’s V-A characteristics equivalent circuit of solar cell