Copper indium diselenide (CIS) layers, which are now showing promise as solar-cell materials, were successfully grown on GaAs (100) substrates using the hot wall epitaxy (HWE) method. The photoconductive CIS layers were grown along the <112> direction having a beneficial gain for solar energy conversion. From the Hall effect measurements, the mobility tended to decrease as a function of T-3/2 in the high temperature range (T > 130 K), and increase as a function of T3/2 in the a low temperature range (T < 50 K). Also, from the photocurrent (PC) measurements, three peaks, A, B, and C, corresponded to the intrinsic transition from the valence band states of Γ 7(A), Γ 6(B), and Γ 7(C) to the conduction band state of Γ 6, respectively. The temperature dependence of the optical band gap obtained by the PC measurements could be expressed by using the empirical equation Eg(T) = Eg(0) - (8.57 × 10-4)T2/(T + 129). By conducting solar cell fabrications, a 14.3% efficiency for n-CdS/p-CIS heterojunction solar-cells was achieved. This achievement suggests that the improved quality of the absorber layer, grown using the HWE method, contributes to the high performance of CIS solar cells.

Keywords: Copper indium diselenide (CIS), mobility, Photocurrent, n-CdS/p-CIS heterojunction solar-cell, Solar energy conversion efficiency.