Abstract
The main purpose of this research is to improve the efficiency of Cu(In,Al)Se2 solar cells by optimizing the selenization process for Cu(In,Al)Se2 absorber layer. We analyzed the quality of the Cu(In,Al) ?Se?_2 films obtained by RF and DC sputter methods using alloy target precursor of Cu-In-Al alloy target with ratio of components (Cu:In:Al) 0.9:0.85:0.15. Same process parameters are used for the selenization of DC sputtered and RF sputtered Cu-In-Al precursor films. DC sputtered Cu-In-Al precursor layer gave rise to better quality Cu(In,Al)Se2 absorber layer after selenization process with better interface between Cu(In,Al)Se2 and Mo layers than in the case of RF sputtered. This provides the advantage of depositing Cu-In-Al precursor layer just after depositing Mo back contact layer in the same DC sputter chamber as an in-line process. Various deposition conditions such as base pressure, selenization process duration, temperature and amount of selenium powder are varied to optimize the process conditions to obtain device quality Cu(In,Al)Se2 films.Finally from the XRD scan and Raman Spectrum analysis we realized that the best Cu(In,Al)Se2 absorber layer can be obtained with a background pressure of 6.8×10^(-7) Torr the selenization duration temperature of 530oC, and the selenization duration of 20 minutes at the heating rate of 50oC/min. And we also deposited Aluminum to improve the structure between the Cu(In,Al)Se2 and Mo adhesion, and added i-ZnO layer between CdS and Al:ZnO layers to improve the open circuit voltage (Voc)and the shunt resistance (R_sh). E- Gun was used to deposit Aluminum as the front electrode to increase the electron collection efficiency in the Cu(In,Al) ?Se?_2 solar cell. The solar cell fabricated with the best Cu(In,Al)Se2 absorber layer showed an efficiency of 2.25% with an open circuit voltage(Voc)of 0.24V, short-circuit current (Jsc) of 25.69mA/cm^(2)and the fill factor (F.F.) of 0.36 for the Cu(In,Al)Se2 solar cell.