Surface Passivation of CIGS Solar Cells Using Gallium Oxide

Abstract

This work proposes gallium oxide grown by plasma‐enhanced atomic layer deposition, as a surface passivation material at the CdS buffer interface of Cu(In,Ga)Se2 (CIGS) solar cells. In preliminary experiments, a metal‐insulator‐semiconductor (MIS) structure is used to compare aluminium oxide, gallium oxide, and hafnium oxide as passivation layers at the CIGS‐CdS interface. The findings suggest that gallium oxide on CIGS may show a density of positive charges and qualitatively, the least interface trap density. Subsequent solar cell results with an estimated 0.5 nm passivation layer show an substantial absolute improvement of 56 mV in open‐circuit voltage (VOC), 1 mA cm−2 in short‐circuit current density (JSC), and 2.6% in overall efficiency as compared to a reference (with the reference showing 8.5% under AM 1.5G).

Insulator Materials for Interface Passivation of Cu(In,Ga)Se2Thin Films

“…For the first studies, Al2O3 was the material of first choice as it is one of the best passivating materials in Si technology. For CIGS, an investigation of other oxide materials was performed as buffer layers in different solar cells configurations [17], [18] and as passivation layer [19] with different insulators than those studied in this work.…”

Optical Lithography Patterning of SiO2 Layers for Interface Passivation of Thin Film Solar Cells

“…compared with reference devices. This study expands the choice of passivation materials already known and its fabrication techniques. The most important conclusion from this paper is that for flat‐Ga ultrathin CIGS solar cells, the pattern of the contacts on the passivation layer is quite important since two competing effects take place.…”

“…In this work, we study rear passivation effects on ultrathin CIGS solar cells. This passivation is performed by applying a SiO 2 layer, in a trench configuration, on top of the rear‐contact electrode (Mo) …”

“…On all the other samples, SiO 2 was implemented as passivation layer, with the following structure: SLG/Mo/SiO 2 /CIGS/CdS/i‐ZnO/ZnO:Al/Ni/Al/Ni grid. The solar cell processing is explained in detail elsewhere and for the CIGS, the layer was co‐evaporated at 550 °C resulting in a thickness of 450 nm and composition [Cu]/([Ga] + [In]) = 0.7, [Ga]/([Ga] + [In]) = 0.3 as measured by X‐ray fluorescence. Na was introduced as a NaF precursor layer with 3 nm.…”

“…This passivation is performed by applying a SiO 2 layer, in a trench configuration, on top of the rear-contact electrode (Mo). [22] Atomic force microscope (AFM) is used in tapping mode with a scan rate of 1 Hz. J-V measurements are performed under a simulated and calibrated AM1.5 spectra (Oriel Instruments -PVIV Test Solution).…”