Highly enhanced p-type electrical conduction in wide band gap Cu1+xAl1−xS2 polycrystals

As potential critical p-type transparency electrode materials applied in solar cells, a series of the Cu- and Zn-doped CuAlS2 samples with band gaps over 3 eV have been prepared, and their optical and electrical properties have been thoroughly investigated. Conductivities as high as 250 S cm−1 are achieved at a Cu doping level of 8 mol%, which are among the highest values known for p-type transparent materials and sufficient for collecting holes in solar cells. A high mobility of 21.2 cm2 V−1 s−1 is also reached at the same doping level. The origin of conductivity enhancement by Cu doping and the structure-optoelectrical property relationship has been elucidated.