Cu(In,Ga)Se2 solar cells fabricated by sputtering from copper-poor and selenium-rich ceramic target with selenium-free post treatment

In this work, copper indium gallium selenide (CIGS) absorbers were prepared by sputtering from a copper-poor and selenium-rich target. The result shows that selenium rich absorbers can be obtained successfully after the annealing treatment under the atmosphere without selenium. The increase of annealing temperature can increase the grain size of the absorber. When the annealing temperature is 450 °C, the conductive type of the absorber is n-type. The corresponding solar cells do not show photovoltaic effects. When the annealing temperature increases from 500 to 550 °C, the mobility and carrier concentration of the absorber increase due to the increased crystallinity. The efficiency increases from 1.3% to 9.2%. When the annealing temperature reaches 600 °C, the increase of the amount of Se vacancies increases the recombination, which reduces Jsc and FF, and consequently decreases the efficiency to 5.9%.