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

In this paper, CuIn0.7Ga0.3Se2 (CIGS) thin films are deposited on both glass (SLG) and glass/SnO2: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 (Ts) 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 (Eg) of about 1.38 eV and 1.24 eV are extracted for CIGS1 and CIGS2, respectively. Besides, activation energies (Ea) 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 cm2/V s and 1.77 cm2/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 (Rs) of about 93.7 Ω and an ideality factor (n) around 3.47 indicate that the generation–recombination mechanism is predominant.