Cu(In,Ga)Se2 thin-film solar cells with an efficiency of 18%

An efficiency of over 18% have been achieved in Cu(In,Ga)Se2 (CIGS) thin-film solar cells. Solar cell parameters were estimated for the cells with efficiencies of more and less than 18%. A diode quality factor n and forward current (saturated current) J0 of the cell with over 18% efficiency are lower than those with below 18% efficiency. This would be attributed to sufficient coverage of the CdS film with excellent uniformity as a buffer and/or window layer over the CIGS film because the process of CdS film formation was improved.