Combustion Synthesis of p-Type Transparent Conducting CuCrO_2+x and Cu:CrO_x Thin Films at 180 °C

Low-temperature solution processing of p-type transparent conducting oxides (TCOs) will open up new opportunities for applications on flexible substrates that utilize low-cost, large-area manufacturing. Here, we report a facile solution synthesis method that produces two p-type TCO thin films: copper chromium oxide and copper-doped chromium oxide. Using combustion chemistry, both films are solution processed at 180 °C, which is lower than most recent efforts. While adopting the same precursor preparation and annealing temperature, we find that annealing environment (solvent vapor vs open air) dictates the resulting film phase, hence the optoelectronic properties. The effect of annealing environment on the reaction mechanism is discussed. We further characterize the electronic, optical, and transport properties of the two materials, and compare the differences. Their applications in optoelectronic devices are successfully demonstrated in transparent p-n junction diodes and as hole transport layers in organic photovoltaic devices.