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- Vermang, Bart, et al.
(författare)
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Introduction of Si PERC Rear Contacting Designto Boost Efficiency of Cu(In,Ga)Se2 Solar Cells
- 2014
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Ingår i: IEEE Journal of Photovoltaics. - 2156-3381 .- 2156-3403. ; 4:6, s. 1644-1649
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Tidskriftsartikel (refereegranskat)abstract
- Recently, Cu(In,Ga)Se-2 (CIGS) solar cells have achieved 21% world-record efficiency, partly due to the introduction of a postdeposition potassium treatment to improve the front interface of CIGS absorber layers. However, as high-efficiency CIGS solar cells essentially require long diffusion lengths, the highly recombinative rear of these devices also deserves attention. In this paper, an Al2O3 rear surface passivation layer with nanosized local point contacts is studied to reduce recombination at the standard Mo/CIGS rear interface. First, passivation layers with well-controlled grids of nanosized point openings are established by use of electron beam lithography. Next, rear-passivated CIGS solar cells with 240-nm-thick absorber layers are fabricated as study devices. These cells show an increase in open-circuit voltage (+57 mV), short-circuit current (+3.8 mA/cm(2)), and fill factor [9.5% (abs.)], compared with corresponding unpassivated reference cells, mainly due to improvements in rear surface passivation and rear internal reflection. Finally, solar cell capacitance simulator (SCAPS) modeling is used to calculate the effect of reduced back contact recombination on high-efficiency solar cells with standard absorber layer thickness. The modeling shows that up to 50-mV increase in open-circuit voltage is anticipated.
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- Vermang, Bart, et al.
(författare)
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Potential-induced optimization of ultra-thin rear surface passivated CIGS solar cells
- 2014
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Ingår i: Physica Status Solidi. Rapid Research Letters. - : Wiley. - 1862-6254 .- 1862-6270. ; 8:11, s. 908-911
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Tidskriftsartikel (refereegranskat)abstract
- Ultra-thin Cu(In,Ga)Se-2 (CIGS) solar cells with an Al2O3 rear surface passivation layer between the rear contact and absorber layer frequently show a roll-over effect in the J-V curve, lowering the open circuit voltage (V-OC), short circuit current (J(SC)) and fill factor (FF), similar to what is observed for Na-deficient devices. Since Al2O3 is a well-known barrier for Na, this behaviour can indeed be interpreted as due to lack of Na in the CIGS absorber layer. In this work, applying an electric field between the backside of the soda lime glass (SLG) substrate and the SLG/rear-contact interface is investi-gated as potential treatment for such Na-deficient rear surface passivated CIGS solar cells. First, an electrical field of +50 V is applied at 85 degrees C, which increases the Na concentration in the CIGS absorber layer and the CdS buffer layer as measured by glow discharge optical emission spectroscopy (GDOES). Subsequently, the field polarity is reversed and part of the previously added Na is removed. This way, the J -V curve roll-over related to Na deficiency disappears and the V-OC (+25 mV), J(SC)(+2.3 mA/cm(2)) and FF (+13.5% absolute) of the rear surface passivated CIGS solar cells are optimized.
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