Effect of annealing dynamics on the ion-engineered CdTe/ZnTe solar cells

Cd1−xZnxTe (CZT)-based matrices have highest absorption capabilities and tunable band gap, so it can be utilized as the central most significant photon absorption layer. In this research, we have briefly investigated the effect of annealing dynamics over the phosphorus ion (P+) implanted Cd1−xZnxTe on different stoichiometric ratios. The P+ ions are introduced at 800 keV in order to tailor/tune the electro-optical characteristics of said ternary compound matrix for its utilization as an active medium in photovoltaic and related application. In this specific study, the annealing dynamics of P+ implanted Cd1−xZnxTe scheme have been studied, and three temperature ranges were chosen ~ 300, 350, and 400 °C for such purpose. The impact of annealing behavior has been envisaged by electrical and electro-optical characterization techniques, i.e., current–voltage (I–V), activation energy, charge-based deep-level transient spectroscopy (Q-DLTS) and transient of photo-voltage (TPV). From Q-DLTS study, one has obtained different defect levels that may limit the overall performance of the as-implant CZT matrix. By adopting RTA process, the damage content in form of trap levels has shifted themselves near premises to their respective band edges i.e., for as-implant cases, the trap level placed near the Fermi level and when the RTA process subjected the trap levels localized themselves to the close proximity to either of its band edge (valance/conduction level), e.g., the trap level of CdTe shift from 0.123 to 0.005 eV, i.e., near the valance band edge which may enhance the trap characteristics. Also, the activation energy and transient of photo-voltage analysis direct the physical importance of RTA process because this process may provide significant increase of carrier’s generation by reduction in activation energy and elevation of photo-voltage by utilizing the appropriate annealing sequence to subject CZT crystal. The TPV analysis of Cd0.75Zn0.25Te sample shows higher extent of physical voltages ~ 63 mV at 400 °C annealing sequences, whereas for as-implant case provides just ~ 10 mV.