Low Frequency and Low Temperature Behavior of Si, solar cell by AC Impedance Measurements

摘要

In this work, the DC measurements and AC measurements (impedance spectra) have been used to characteristic the Si-module solar cell 6x6 (36 cells), 3.8 V and 85 mA. From the I-V characteristics under dark conditions for different temperatures (300-350 K°) and by using the ARREHENIUS diagrams defined by Ln(I)=f(l/T)|_(v=const), we have obtained the barrier height Ψ (eV), ideal factor A, and the reverse saturation current I_o (uA); which equal to 0.322 eV, 2.83 and 0.831 uA, respectively. The AC measurement impedance [X((n)=f(R((a))] has been employed to measure the parameters of the Si- module solar cell such as: heterogeneity factor, p, DC resistance R_(dc), the bulk resistance R_b, activation energy E (eV), donor density N_d (cm~(-3)), and density states N_s (cm~(-2)). The solar cell module was exposed to thermal stress within the range (300-350 K°), the diagram of complex impedance in the dark, was obtained. This plot gives arcs of a semicircle, their centers lie below the real axis R(ω), corresponding to the appearance of the depression angle (0≠0) which represents, β (β=2θ/π) which is in good agreement with the Cole-Cole diagram. It is noted that, P, increases with temperature. The intersection of the circle arcs from the right with x axis (i.e. at very low frequency) gives R_(dc), (105 KΩ), while the intersection from the left gives R_v, of the sample (2.77 KΩ) (i.e. at very high frequency). By using ARREHENIUS diagrams defined by Ln(f)=f(l/T), we have obtained the parameters E (eV), N_d (cm~(-3)), and Ns (cm~(-2)), which equal to 0.354 eV, 1.38x 10~(13) cm~(-3) and 6.93x 10~9 cm~(-2) respectively.