Effect of spectral response of solar cells on the module output whenindividual cells are shadedBaishali Talukdara,b , Sukanya Buragohain a , Sanjai Kumar c , V. Umakanth c , Nabin Sarmah a ,Sadhan Mahapatraa, ⇑a Department of Energy, Tezpur University, Tezpur 784028, Assam, Indiab Department of Electrical Engineering, Girijananda Chowdhury Institute of Management and Technology, Tezpur 784501, Assam, Indiac Solar Photovoltaic Group, Central Electronics Limited, Sahibabad 201010, Indiaa r t i c l e i n f oArticle history:Received 4 May 2016Received in revised form 9 August 2016Accepted 19 August 2016Available online 24 August 2016Keywords:Spectral responseSolar cellShadingPhotovoltaicQuantum eff i ciencya b s t r a c tSolar cell characterization is carried out by current-voltage (I-V) and spectral response measurements.These characteristics of the solar cell depend on solar cell design, fabrication, material properties, junc-tion depth and optical coatings. Generally, during module manufacturing, solar cells of similar wattageare used and spectral response (SR) including external quantum eff i ciency (EQE) and internal quantumeff i ciency (IQE) characteristics are not given any attention. It is observed that similar wattage rating crys-talline solar cells have slight variation in their spectral response behavior over the wavelength range(300–1100 nm). In this paper, the effect of shading on the crystalline solar cells of the module havingsame power output and slight difference in spectral response are experimentally investigated. The max-imum and minimum drop in short circuit current of the module is observed to be 84.2% and 34.6% whenthe solar cells of high and low spectral response are shaded. Minority carrier diffusion length and deadlayer thickness parameters of solar cells are also calculated from the short and long wavelength regionof the spectral response curve. It is found that the effect on module output is high in case of shading acell having maximum diffusion length and minimum dead layer length. It is concluded that spectralresponse of a solar cell is an additional parameter that must be considered apart from cell I-V character-istics in module fabrication for superior and uniform performance in the f i eld.? 2016 Elsevier Ltd. All rights reserved.1. IntroductionPhotovoltaic (PV) module power output primarily depends onthe performance of solar cells used in the module fabrication.The characterization of solar cells is done by I-V characteristicsand the conversion eff i ciency depends on the photo-generated cur-rent which is strongly related with quantum eff i ciency. The quan-tum eff i ciency corresponds to the spectral response whichdetermines the spectral distribution effect on the short-circuit cur-rent (Yang et al., 2008). The spectral response curve depicts thecrystalline solar cell output relative to constant energy input at dif-ferent wavelengths range from approximately 300–1200 nm(Luque and Hegedus, 2011).Experimental investigations on the effect of spatial variation ofincident radiation on the spectral response of solar cells and mod-ules have been carried out by different researchers. Rüther et al.(2002) monitored and compared the outdoor operation of amor-phous silicon (a-Si) solar modules with that of crystalline silicon(c-Si) technology and concluded that a-Si are more eff i cient in win-ter contrast to c-Si solar cells which perform better during sum-mer. Okullo et al. (2011) and Ghitas (2012) investigated thequantitative effects of the solar spectral variations on the perfor-mance of multi-crystalline silicon photovoltaic modules and con-cluded that visible region contribute maximum towards shortcircuit current compared to infrared or ultraviolet region. Lombezet al. (2014) carried out a micrometric investigation of EQE onmicrocrystalline CuInGa(S,Se) 2 solar cells and observed differentspatial f l uctuation ranges. Micrometric variations are also observedwhich are attributed to intrinsic properties of the poly-crystallineabsorbers whereas longer range f l uctuations are linked to the fab-rication process of the microcell. Fernández et al. (2014) studiedthe spectral variations on the performance of high concentratorphotovoltaic modules operating under different real climatic con-ditions and found that the annual spectral losses vary from 6% to51% depending on the location and the module. As a non-destructive technique, IQE has also become an important solar cellhttp://dx.doi.org/10.1016/j.solener.2016.08.0320038-092X/? 2016 Elsevier Ltd. All rights reserved.⇑ Corresponding author.E-mail address: sadhan.mahapatra@gmail.com (S. Mahapatra).Solar Energy 137 (2016) 303–307Contents lists available at ScienceDirectSolar Energyjournal homepage: www.elsevier.com/locate/solener
