Silver Surface Treatment of Cu(In,Ga)Se₂ (CIGS) Thin Film: A New Passivation Process for the CdS/CIGS Heterojunction Interface

Abstract

The interface engineering of Cu(In,Ga)Se2 (CIGS)‐based solar cells is challenging for high‐efficiency devices, especially for the CdS/CIGS heterojunction interface. Recently, post‐treatment of the CIGS surface, as an efficient approach to passivate the defects at the CdS/CIGS interface, has attracted widespread attention. Here, a simple Ag surface treatment process is used to realize the passivation of interface defects and the enhancement of the CdS/CIGS heterojunction. This process not only reduces the surface roughness of CIGS films significantly, but also contributes to controlling the Ga composition in the surface layer. Furthermore, characterization techniques reveal that Ag surface treatment can effectively decrease the defect concentrations at the heterojunction interface and enhance the CdS/CIGS heterojunction quality with appropriate Ag deposition duration. Further investigations on the changed defect level caused by the Ag surface treatment indicate that the increased defect level is likely related to the shift of valence band maximum. Eventually, the efficiency of the optimum device has a relative increase of about 18% compared with that of the reference solar cell. This work focuses on revealing the differences of the CIGS surface and CdS/CIGS interface caused by Ag, which provides a new surface processing method for the passivation of the CdS/CIGS heterojunction.

Enhancing Surface Properties for Electrodeposited Cu(In,Ga)Se2 Films by (NH4)2S Solution at Room Temperature

“…It is observed that the GIXRD patterns of the treated sample (10 min) slightly shift to lower diffraction angles compared with the reference sample. Based on the standard equation for the tetragonal lattice , the lattice constants of the CIGS films is also calculated: the 0 min sample, 5.7028 Å for a and 11.4718 Å for c ; the 10 min sample, 5.7379 Å for a and 11.4937 Å for c . These results suggest an increase in the lattice constants of the CIGS films with the AS treatment.…”

Facile Silver-Incorporated Method of Tuning the Back Gradient of Cu(In,Ga)Se2 Films

“…The doping concentrations (N A ) of these two samples are 6.91 × 10 15 cm −3 , and 5.26 × 10 15 cm −3 in Figure S1 in the Supporting Information. According to the references, the relationship of ΔV oc and N A can be expressed by 31,32…”

“…The doping concentrations ( N A ) of these two samples are 6.91 × 10 15 cm –3 , and 5.26 × 10 15 cm –3 in Figure S1 in the Supporting Information. According to the references, the relationship of Δ V oc and N A can be expressed by , where k B is the Boltzmann constant, T is the temperature, and q is the elementary charge, respectively. Equation is fit for our results that a lower N A corresponds to a lower V oc .…”

“…Finally, the Ni−Al grid was grown by the e-beam as the front contact with a mask. 21,32 In this work, five group samples are compared to study the effect of doping CIGS films with Ag on the back gradient and the corresponding device performance. The reference sample is the CIGS film without any Ag doping (0 min).…”

“…Afterwards, i-ZnO and Al-doped ZnO layers were prepared by a sputtering method. Finally, the Ni–Al grid was grown by the e-beam as the front contact with a mask. , …”