CuIn0.7Ga0.3Se2 thin films’ properties grown by close-spaced vapor transport technique for second-generation solar cells

Abstract

In this paper, CuIn 0.7 Ga 0.3 Se 2 (CIGS) thin films are deposited on both glass (SLG) and glass/SnO 2 :F (SLG/FTO) substrates, by close-spaced vapor transport technique. The Hall effect measurements are performed in the temperature range (300-438 K) for the two SLG/CIGS samples namely CIGS1 and CIGS2, grown at substrate temperature (T s ) of 470 °C and 510 °C, respectively, to investigate the temperature effect on the electrical parameters such as hole concentration (p), conductivity (σ) and mobility (µ). As results, from Arrhenius diagram of (p) and (σ), bandgap energy (E g ) of about 1.38 eV and 1.24 eV are extracted for CIGS1 and CIGS2, respectively. Besides, activation energies (E a ) at 563.9 meV and 239.4 meV are determined for CIGS1 whereas values at 584.2 meV and 72.7 meV are obtained for CIGS2. Furthermore, average mobilities of 1.83 cm 2 /V s and 1.77 cm 2 /V s are achieved for CIGS1 and CIGS2 thin films, respectively. Pure aluminum (Al) Schottky contacts are deposited on the front side of FTO/CIGS thin film-devices by physical vapor deposition. Current-voltage (I-V) characteristics are measured and used to extract the electrical parameters of FTO/CIGS/Al Schottky diode using the one diode model. The electrical parameters including series resistance (R s ) of about 93.7 Ω and an ideality factor (n) around 3.47 indicate that the generation-recombination mechanism is predominant.

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