Critical design criteria for silicon nanocrystals downshifting layers enhancement in CIGS solar cells

Abstract. Conventional Cu  (  In  ,  Ga  )  Se2 (CIGS) solar cells suffer poor response in the short-wavelength region (280 to 520 nm) due to the parasitic absorption in the ZnO transparent conductive oxide and inefficient collection of generated electron–hole pairs in the CdS layer. The short-wavelength response can be enhanced using a downshifting (DS) layer mounted on the top surface of the solar cell. The performance effects of coupling silicon nanocrystals DS layer to a CIGS solar cell are analyzed using numerical simulations. Measured photoluminescence of fabricated Si-nC using plasma-enhanced chemical vapor deposition is used to calibrate the model. A 13.9% relative enhancement of the conversion efficiency is observed when a DS layer with a photoluminescence quantum yield (PLQY) of 20% is added. The relative enhancement increases to 17.8% when the DS layer has a PLQY of 100%. The results are further analyzed to decouple and quantify the surface reflectance effect and the DS effect using a passive cell. The surface reflectance effect is dominant for DS layers with PLQY of 20% and accounts for 13.6% relative enhancement. Whereas the DS effect dominates when the PLQY is >70  %   and reaches 17.1% relative enhancement for a DS layer with PLQY of 100%. Overall, cells with poor UV spectral responses are found to benefit the most from the coupling of a DS layer, albeit only for a very high PLQY.

[1]  Harry A. Atwater,et al.  Photoluminescence quantum efficiency of dense silicon nanocrystal ensembles in SiO2 , 2006 .

[2]  J. C. Muller,et al.  Silicon nanocrystals as light converter for solar cells , 2004 .

[3]  M. Green,et al.  Improving solar cell efficiencies by down-conversion of high-energy photons , 2002 .

[4]  Bryce S. Richards,et al.  Increase in short-wavelength response of encapsulated CIGS devices by doping the encapsulation layer with luminescent material , 2012 .

[5]  Grace M. Credo,et al.  External quantum efficiency of single porous silicon nanoparticles , 1999 .

[6]  Lorenzo Pavesi,et al.  Modeling of silicon nanocrystals based down-shifter for enhanced silicon solar cell performance , 2012 .

[7]  Oscar D. Crisalle,et al.  Device modeling and simulation of the performance of Cu(In1−x,Gax)Se2 solar cells , 2004 .

[8]  W. Shafarman,et al.  Optical characterization of CuIn1−xGaxSe2 alloy thin films by spectroscopic ellipsometry , 2003 .

[9]  Jae‐Hyung Jang,et al.  Ultrawide Spectral Response of CIGS Solar Cells Integrated with Luminescent Down-Shifting Quantum Dots. , 2017, ACS applied materials & interfaces.

[10]  K. McIntosh,et al.  Overcoming the poor short wavelength spectral response of CdS/CdTe photovoltaic modules via luminescence down‐shifting: ray‐tracing simulations , 2007 .

[11]  T. Hall,et al.  Numerical modeling of silicon nanocrystal down-shifting layers for enhanced CIGS solar cell performance , 2013, 2013 IEEE 39th Photovoltaic Specialists Conference (PVSC).

[12]  K. Hinzer,et al.  Modeling down-conversion and down-shifting for photovoltaic applications , 2012, 2012 38th IEEE Photovoltaic Specialists Conference.

[13]  U. Zimmermann,et al.  Baseline model of graded-absorber Cu(In,Ga)Se2 solar cells applied to cells with Zn1 − xMgxO buffer layers , 2011 .

[14]  Kristiaan Neyts,et al.  Simulation of light emission from thin-film microcavities , 1998 .

[15]  Uwe R. Kortshagen,et al.  Plasma synthesis and liquid-phase surface passivation of brightly luminescent Si nanocrystals , 2006 .

[16]  Steven S. Hegedus,et al.  Thin‐film solar cells: device measurements and analysis , 2004 .

[17]  M. Fujii,et al.  Size dependence of photoluminescence quantum efficiency of Si nanocrystals , 2006 .

[18]  Mher Ghulinyan,et al.  Silicon solar cells with nano-crystalline silicon down shifter: experiment and modeling , 2010, Optics + Photonics for Sustainable Energy.

[19]  C. Brabec,et al.  Nanostructured organosilicon luminophores in highly efficient luminescent down-shifting layers for thin film photovoltaics , 2016 .

[20]  Uwe R. Kortshagen,et al.  Silicon nanocrystals with ensemble quantum yields exceeding 60 , 2006 .

[21]  W. Warta,et al.  Solar cell efficiency tables (version 50) , 2017 .

[22]  W. Warta,et al.  Solar cell efficiency tables (version 49) , 2017 .

[23]  W. V. Sark,et al.  Enhancing solar cell efficiency by using spectral converters , 2005 .

[24]  Karin Hinzer,et al.  Modeling a monocrystalline Cu(In,Ga)Se2 single junction solar cell grown on a GaAs substrate , 2013, Other Conferences.

[25]  T. Gregorkiewicz,et al.  Space-separated quantum cutting with silicon nanocrystals for photovoltaic applications , 2008 .

[26]  Stephen Glynn,et al.  Required material properties for high-efficiency CIGS modules , 2009, Optics + Photonics for Sustainable Energy.

[27]  A. Morales-Acevedo,et al.  Modeling solar cells: A method for improving their efficiency , 2012 .

[28]  K. Hinzer,et al.  Procedure to decouple reflectance and down-shifting effects in luminescent down-shifting enhanced photovoltaics. , 2017, Optics express.

[29]  K. Hinzer,et al.  Quantum efficiency measurements of down-shifting using silicon nanocrystals for photovoltaic applications , 2012, 2012 38th IEEE Photovoltaic Specialists Conference.

[30]  B. Richards,et al.  Increased mc-Si Module Efficiency Using Fluorescent Organic Dyes: A Ray-Tracing Study , 2006, 2006 IEEE 4th World Conference on Photovoltaic Energy Conference.

[31]  J. Sites,et al.  Band-gap grading in Cu(In,Ga)Se2 solar cells , 2005 .

[32]  Lorenzo Pavesi,et al.  Silicon nanocrystals as a photoluminescence down shifter for solar cells , 2011 .

[33]  U. Rau,et al.  Improvement of photon collection in Cu(In, Ga)Se2 solar cells and modules by fluorescent frequency conversion , 2007 .