Growth Mechanism and Current-Voltage Characteristics of Co-Evaporated Cu(In,Ga)Se2 Thin Film with Various Cu Contents

초록

In this study, Cu(In1-xGax)Se-2 thin films were prepared and characterized. The CIGS thin films were characterized by scanning electron microscopy, four-point probe measurement, Hall measurement and I-V measurement. Cu/(Ga + In) ratios were varied between 0.4 and 1.09. As the Cu content increased, the grain size of CIGS film became bigger. As the Cu composition increased, the resistivity decreased from 116 Omega . cm to 5.9 x 10(-3) Omega . cm. The carrier concentration increased from 1.54 x 10(15) cm(-3) to 3.39 x 10(18) cm(-3) with increases in the Cu composition. The Hall mobility showed the peak value of 812 cm(2)/V . s with the Cu/(Ga + In) ratio of 0.88. At the Cu composition of 0.88, the lowest ideal coefficient of 1.89 was obtained in the space charge region and the lowest saturation current of 7.14 x 10(-5) mA/cm(2). The ideality factor was 1 similar to 2. These results indicated that the bulk recombination occurs in the defects of depletion layer. Similarly, in a quasi-neutral region, we obtained the lowest ideal coefficient of 4.90 and the lowest saturation current of 5.02 x 10(-7) mA/cm(2) with the Cu/(Ga + In) ratio of 0.88.

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