Recombination Losses in Solar Cells Based on n-ZnS(n-CdS) / p-CdTe Heterojunctions (original) (raw)
Related papers
The optical and recombination losses in auxiliary and absorbing layers of solar cells based on hetero-junctions n-ZnS / p-CdTe and n-CdS / p-CdTe with current collecting front sublayers ITO and ZnO were determined. As a result, spectral dependence of light transmittance (T) of solar cells, taking into account its reflections from the boundaries of the contacting materials and in case of absorption in the auxiliary layers of solar cells was calculated. The influence of optical and recombination losses in the solar cell structure ITO (ZnO) / CdS (ZnS) / CdTe on the short circuit current (Jsc) and efficiency (h) of solar cells with different thickness of the window layer CdS (ZnS) (50-300 nm) and constant current collecting layer (200 nm) was investigated. It has been established that the greatest efficiency values (15.9-16.1%) solar cells have the structure of ZnO / ZnS / CdTe at a concentration of uncompensated acceptors in the absorbent layer (Na – Nd) = 10 15-10 17 cm – 3 and the window layer thickness of 50 nm.
Optical Losses of Thin Solar Cells on the Basis of n-ZnS / p-CdTe and n-CdS / p-CdTe Heterojunctions
The optical reflection and absorption losses in the accessory layers of solar cells based on n-ZnS / p-CdTe and n-CdS / p-CdTe heterojunctions are defined in this work. Aluminum doped zinc oxide is used as the front conductive layer material. It is shown that the replacement of traditional window material (CdS) for a wide-one (ZnS) leads to an increase in accessory solar cells layers transmittance. When the thickness of the window layers is 50 nm, the transmittance using ZnS windows with the wavelength of 380-500 nm is higher in 7-40 % than the corresponding value for CdS. At 300 nm for the same spectral field the difference increases to 8-89 %.
Effect of interface recombination on solar cell parameters
Solar Energy Materials and Solar Cells, 2003
A model is presented for p-n hetero-junction solar cells in which interface recombination is the dominant diode current transport mechanism. The model explains the large diode ideality factor (n > 2) and the increased saturation current density in terms of increased density of interface states N ir : Furthermore, the model allows us to explain the non-translation between illuminated and dark J2V characteristics. The explanation is based on the assumption that, for high interface state density values, both the depletion layer width and the diffusion voltage in the p-and n-side of the junction are functions of N ir : The interface recombination leads to lower values of the open-circuit voltage, short-circuit current density, and fill factor. These results are illustrated by numerical calculations of solar cell parameters and compared with experimental data achieved for ZnO/CdS/CuGaSe 2 single-crystal solar cells.
2021
A CdS thin film buffer layer has been widely used as conventional n-type heterojunction partner both in established and emerging thin film photovoltaic devices. In this study, we perform numerical simulation to elucidate the influence of electrical properties of the CdS buffer layer, essentially in terms of carrier mobility and carrier concentration on the performance of SLG/Mo/p-Absorber/n-CdS/n-ZnO/Ag configured thin film photovoltaic devices, by using the Solar Cell Capacitance Simulator (SCAPS-1D). A wide range of p-type absorber layers with a band gap from 0.9 to 1.7 eV and electron affinity from 3.7 to 4.7 eV have been considered in this simulation study. For an ideal absorber layer (no defect), the carrier mobility and carrier concentration of CdS buffer layer do not significantly alter the maximum attainable efficiency. Generally, it was revealed that for an absorber layer with a conduction band offset (CBO) that is more than 0.3 eV, Jsc is strongly dependent on the carrier ...
International Journal for Research in Applied Science and Engineering Technology (IJRASET), 2018
In this work, CdS, ZnS and ZnO thin films have been deposited by chemical bath deposition technique and dried at 150 0 C for 30 min. Detail optical and structural characterizations have been done by UV-Vis spectroscopy and X-ray Diffraction analysis to get a comparative study between 3 samples. The XRD analysis has revealed that CdS and ZnO have hexagonal wurtzite crystal structures while ZnS has Zinc blend crystal structure. Lattice parameter and crystallite size were also measured from XRD. From UV spectra it is seen that ZnS and ZnO have transmittance in the range of (85-90) % which was greater than that of CdS. Deposited CdS, ZnS and ZnO reportedly have band gaps of 2.0 eV, 3.63 eV and 3.65 eV respectively. It is proposed that among 3 samples ZnO has more suitable properties as the window layer for thin film solar cell.
Mitigating Reasons for the Poor Performance of n-CdS/p-SnS Solar Cells
Global Challenges
an extra Zn-based (mainly ZnO) buffer layer in the structure or inverting the cell geometry. [14-17] Although the p-SnS solar cell performance has improved by adding the extra buffer layer, these results fail to comment upon the factors effecting the pristine CdS/SnS junction which leads to the need of a buffer layer. This, hence implies serious gaps exist in our understanding of p-SnS based heterojunction solar cells which needs to be addressed in order to improve SnS based solar cell's performance. A solar cell consists of three regions, namely a) the junction region, b) the neutral region, and finally c) the electrodes. A drop in performance of any one of the three regions would result in a substantial drop in the device performance. In our previous report, [18] detailing our extensive study on p-SnS thin films properties as a function of film thickness, we had shown that the diffusion length of holes through the neutral region would play an important role in deciding the solar cell's conversion efficiency. Based on the results of that study, we claimed that a p-SnS active layer of 900 nm thickness would be best suited for solar cell application. The aim of this manuscript is to study the effect of SnS thin film properties on the heterojunction formed with CdS layer and to investigate the reasons for the poor efficiency reported to date for pristine n-CdS/p-SnS solar cells.
FUOYE Journal of Engineering and Technology, 2020
p-ZnTe thin film semiconductors have been successfully used as an absorber material to n-CdS window layer by effectively optimising the ZnTe absorber layer thickness. In order to create a two terminal hetero-junction diode from the n- and p- type materials, two ohmic electrical contacts are required. This was achieved by depositing n-CdS layers on glass/fluorine-doped tin oxide (FTO) conducting substrate and evaporating Au on p-ZnTe layer. The ZnTe layer was successfully electroplated on CdS thin film grown on glass/fluorine-doped tin oxide (FTO) conducting substrates. The device structures were subjected to heat treatment in air with and without CdCl2 surface treatment using temperature of 400oC and duration of 10 minutes. The incorporation of the CdCl2 treatment led to enhancement in the solar cell efficiency. Solar cells developed from glass/FTO/n-CdS/p-ZnTe/Au device structure gave an open circuit voltage (Voc) of 450 mV, short circuit current density (Jsc) of 7.26 mAcm-2 and fi...
Influence of P+-ZnTe back surface contact on photovoltaic performance of ZnTe based solar cells
Optical and Quantum Electronics
In order to improve photovoltaic performance of solar cells based on ZnTe thin films two device structures have been proposed and its photovoltaic parameters have been numerically simulated using Solar Cell Capacitance Simulator software. The first one is the ZnO/CdS/ZnTe conventional structure and the second one is the ZnO/CdS/ZnTe/P +-ZnTe structure with a P +-ZnTe layer inserted at the back surface of ZnTe active layer to produce a back surface field effect which could reduce back carrier recombination and thus increase the photovoltaic conversion efficiency of cells. The effect of ZnO, CdS and ZnTe layer thicknesses and the P +-ZnTe added layer and its thickness have been optimized for producing maximum working parameters such as: open-circuit voltage Voc, short-circuit current density Jsc, fill factor FF, photovoltaic conversion efficiency η. The solar cell with ZnTe/P +-ZnTe junction showed remarkably higher conversion efficiency over the conventional solar cell based on ZnTe layer and the conversion efficiency of the ZnO/CdS/ZnTe/P +-ZnTe solar cell was found to be dependent on ZnTe and P +-ZnTe layer thicknesses. The optimization of ZnTe, CdS and ZnTe layers and the inserting of P +-ZnTe back surface layer results in an enhancement of the energy conversion efficiency since its maximum has increased from 10% for ZnO, CdS and ZnTe layer thicknesses of 0.05, 0.08 and 2 µm, respectively to 13.37% when ZnO, CdS, ZnTe and P +-ZnTe layer thicknesses are closed to 0.03, 0.03, 0.5 and 0.1 µm, respectively. Furthermore, the highest calculated output parameters have been Jsc = 9.35 mA/cm 2 , Voc = 1.81 V, η=13.37% and FF= 79.05% achieved with ZnO, CdS, ZnTe, and P +-ZnTe layer thicknesses about 0.03, 0.03, 0.5 and 0.1 µm, respectively. Finally, the spectral response in the long-wavelength region for ZnO/CdS/ZnTe solar cells has decreased at the increase of back surface recombination velocity. However, it has exhibited a red shift and showed no dependence of back surface recombination velocity for ZnO/CdS/ZnTe/P+-ZnTe solar cells.
Study on the ITO/ZnO interface and its effect on CdS/CdTe solar cell performance
2015
ZnO thin films have been deposited on ITO coated glass substrates, using RF magnetron reactive sputtering from a Zn target . The ZnO film s were annealed at 5 6 0 °C for 1 hour, in order to promote the diffusion of the ITO into ZnO. The properties of the samples were analyzed by X - ray diffraction (XRD), UV - Vis spectroscopy and X - ray photoelectron spectroscopy (XPS) . The ITO/ZnO interface showed a diffusion of 50 nm approximately. In order to study the effect of ZnO thickness, in the performance of the CdS/CdTe solar cell, we used an AMPS - 1D solar simulator; the results showed that reduction of the ZnO thickness had a weak influence in the efficiency of the solar cell.
In this paper a modeling of the main working parameters, such as: open-circuit voltage Voc, short-circuit current density Jsc, fill factor FF, efficiency h of solar cells based on ZnTe/CdSe and ZnSe/CdSe hetero-junctions (HJ) depend on the external conditions: operation temperature, absorption and window layers thickness. Were determined a basic parameters for obtaining solar cells with optimal efficiency of light irradiation conversion.