Structure and electrical characteristics of hot wall deposited CuInSe2 thin films and study on back contact layers in CuInSe2 based solar cells

CuInSe2 thin films were prepared on to well cleaned glass substrates by a hot wall deposition technique. The X-ray diffraction studies revealed that all the deposited films are polycrystalline in nature, single phase, and exhibiting chalcopyrite structure. The crystallites were found to have a preferred orientation along the (112) direction. The resistivity is found to decrease with increase in temperature. Two types of conduction mechanisms are present in the hot wall deposited CuInSe2 films. In the temperature region below 215 K the conduction is due to variable range hopping mechanism and in the temperature region above 215 K the conduction is due to thermally activated process. It is observed that the solar cell with molybdenum as back contact has low series resistance (R-s), high shunt resistance (R-sh) and large fill factor (IF) when compared with CuInSe2 based solar cells with other back contact material layers.