Abstract
In this paper, we propose an optimized structure of thin Cu(In,Ga)Se2 (CIGS) solar cells with a grating aluminum oxide (Al2O3) passivation layer (GAPL) providing nano-sized contact openings in order to improve power conversion efficiency using optoelectrical simulations. Al2O3 is used as a rear surface passivation material to reduce carrier recombination and improve reflectivity at a rear surface for high efficiency in thin CIGS solar cells. To realize high efficiency for thin CIGS solar cells, the optimized structure was designed by manipulating two structural factors: the contact opening width (COW) and the pitch of the GAPL. Compared with an unpassivated thin CIGS solar cell, the efficiency was improved up to 20.38% when the pitch of the GAPL was 7.5–12.5 μm. Furthermore, the efficiency was improved as the COW of the GAPL was decreased. The maximum efficiency value occurred when the COW was 100 nm because of the effective carrier recombination inhibition and high reflectivity of the Al2O3 insulator passivation with local contacts. These results indicate that the designed structure has optimized structural points for high-efficiency thin CIGS solar cells. Therefore, the photovoltaic (PV) generator and sensor designers can achieve the higher performance of photosensitive thin CIGS solar cells by considering these results.
Highlights
We investigated thin CIGS solar cells’ performance tendency by
The fill factor (FF) and efficiency improved in wider contact opening width (COW) ranges, with half andat the M
Than in the unpassivated thin CIGS solar cells were shown in the entire range and pitches
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The insufficient thickness of the active layer lowers the absorption of incident sunlight Another efficiency loss comes from strong carrier recombination occurring at the rear interface between the molybdenum (Mo) emitter and thin CIGS absorber layer [24,25]. To suppress this carrier recombination, a passivation layer with local contacts is inserted into the rear interface, effectively reducing the direct contact area between Mo and CIGS [24,25,26] It can increase the internal light reflection of the rear contacts, absorbing a larger amount of light into a thin CIGS layer [25,27]. This study suggests a way to realize high-efficiency thin solar cells for PV generators and sensors
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