A simple synthesis of transparent and highly conducting p-type Cu(x)Al(1−x)S(y) nanocomposite thin films as the hole transporting layer for organic solar cells

Inorganic p-type films with high mobility are very important for opto-electronic applications. It is very difficult to synthesize p-type films with a wider, tunable band gap energy and suitable band energy levels. In this research, p-type copper aluminum sulfide (Cu(x)Al(1−x)S(y)) films with tunable optical band gap, carrier density, hole mobility and conductivity were first synthesized using a simple, low cost and low temperature chemical bath deposition method. These in situ fabricated Cu(x)Al(1−x)S(y) films were deposited at 60 °C using an aqueous solution of copper(ii) chloride dihydrate (CuCl(2)·2H(2)O), aluminium nitrate nonohydrate [Al(NO(3))(3)·9H(2)O], thiourea [(NH(2))(2)CS], and ammonium hydroxide, with citric acid as the complexing agent. Upon varying the ratio of the precursor, the band gap of the Cu(x)Al(1−x)S(y) films can be tuned from 2.63 eV to 4.01 eV. The highest hole mobility obtained was 1.52 cm(2) V(−1) s(−1) and the best conductivity obtained was 546 S cm(−1). The Cu(x)Al(1−x)S(y) films were used as a hole transporting layer (HTL) in organic solar cells (OSCs), and a good performance of the OSCs was demonstrated using the Cu(x)Al(1−x)S(y) films as the HTL. These results demonstrate the remarkable potential of Cu(x)Al(1−x)S(y) as hole transport material for opto-electronic devices.