Electrical bias as an alternate method for reproducible measurement of copper indium gallium diselenide (CIGS) photovoltaic modules

Light-to-dark metastable changes in thin-film photovoltaic (PV) modules can introduce uncertainty when measuring module performance on indoor flash testing equipment. This study describes a method to stabilize module performance through forward-bias current injection rather than light exposure. Measurements of five pairs of thin-film copper indium gallium diselenide (CIGS) PV modules indicate that forward-bias exposure maintained the PV modules at a stable condition (within 1%) while the unbiased modules degraded in performance by up to 12%. It was also found that modules exposed to forward bias exhibited stable performance within about 3% of their long-term outdoor exposed performance. This carrier-injection method provides a way to reduce uncertainty arising from fast transients in thin-film module performance between the time a module is removed from light exposure and when it is measured indoors, effectively simulating continuous light exposure by injecting minority carriers that behave much as photocarriers do. This investigation also provides insight into the initial light-induced transients of thin-film modules upon outdoor deployment.

[1]  J. Sites,et al.  TIME DEPENDENT VOLTAGE IN CuInSe2 AND CdTe SOLAR CELLS , 1993 .

[2]  A. Rothwarf,et al.  Time-dependent open-circuit voltage in CuInSe2/CdS solar cells: theory and experiment , 1987 .

[3]  Michael Gostein,et al.  Light soaking effects on photovoltaic modules: Overview and literature review , 2011, 2011 37th IEEE Photovoltaic Specialists Conference.

[4]  B. Marion.  Comparison of predictive models for photovoltaic module performance , 2008, 2008 33rd IEEE Photovoltaic Specialists Conference.

[5]  Marika Edoff,et al.  Metastabilities in the electrical characteristics of CIGS devices : Experimental results vs theoretical predictions , 2007 .

[6]  Alex Zunger,et al.  Intrinsic DX centers in ternary chalcopyrite semiconductors. , 2008, Physical review letters.

[7]  Alex Zunger,et al.  Light- and bias-induced metastabilities in Cu(In,Ga)Se2 based solar cells caused by the (VSe-VCu) vacancy complex , 2006 .

[8]  Joop Schoonman,et al.  Investigation of capacitance transients in CuInS2 due to ionic migration , 2008 .

[9]  Jean-François Guillemoles,et al.  Stability Issues of Cu(In,Ga)Se2-Based Solar Cells , 2000 .

[10]  Susanne Siebentritt,et al.  The electronic structure of chalcopyrites—bands, point defects and grain boundaries , 2010 .

[11]  S. Kurtz,et al.  Thin-film reliability trends toward improved stability , 2011, 2011 37th IEEE Photovoltaic Specialists Conference.

[12]  J. A. del Cueto,et al.  Progress toward a stabilization and preconditioning protocol for polycrystalline thin-film photovoltaic modules , 2010, 2010 35th IEEE Photovoltaic Specialists Conference.

[13]  Uwe Rau,et al.  Metastable electrical transport in Cu(In,Ga)Se2 thin films and ZnO/CdS/Cu(In,Ga)Se2 heterostructures☆ , 1998 .

[14]  Chris Deline,et al.  Metastable electrical characteristics of polycrystalline thin-film photovoltaic modules upon exposure and stabilization , 2012 .