Importance of electron current in p-type CdTe in CdS/CdTe thin film solar cells at forward bias

2001 ◽  
Vol 668 ◽  
Author(s):  
Jutta Beier ◽  
Marc Köntges ◽  
Peter Nollet ◽  
Stefaan Degrave ◽  
Marc Burgelman
Keyword(s):  
Thin Film ◽  
Solar Cells ◽  
Minority Carrier ◽  
Voltage Dependence ◽  
Forward Bias ◽  
Back Contact ◽  
Cdte Solar Cells ◽  
Dependent Behavior ◽  
Measurement Results ◽  
P Type

ABSTRACTIn previous work [1,2], we modeled the cross-over of the I-V curves of thin film CdS/CdTe solar cells in terms of an electron (minority carrier) current in the vicinity of the back contact. In this work, we focus on the necessary extension of this analytical model based on a series of measurement results. Especially the wavelength and voltage dependence of the current at forward bias is illustrated in these measurements. The various possible causes for this kind of behavior are discussed and modeled. The extensions to the previous model, needed to describe the voltage and wavelength dependent behavior of I-V curves of real CdTe/CdS solar cells, are proposed.

First-principles Study of Back Contact Effects on CdTe Thin Film Solar Cells

2010 ◽  
Vol 1268 ◽  
Author(s):  
Mao-Hua Du
Keyword(s):  
Thin Film ◽  
Solar Cells ◽  
First Principles ◽  
Cell Performance ◽  
Thin Film Solar Cells ◽  
Back Contact ◽  
Cdte Thin Film ◽  
Solar Cell Performance ◽  
Cdte Solar Cells ◽  
P Type

AbstractForming a chemically stable low-resistance back contact for CdTe thin film solar cells is critically important to the cell performance. This paper reports theoretical study of the effects of the back contact material, Sb2Te3, on the performance of the CdTe solar cells. First-principles calculations show that Sb impurities in p-type CdTe are donors and can diffuse with low diffusion barrier. There properties are clearly detrimental to the solar cell performance. The Sb segregation into the grain boundaries may be required to explain the good efficiencies for the CdTe solar cells with Sb2Te3 back contacts.

scholarly journals Nanocomposite (CuS) (ZnS)1 thin film back contact for CdTe solar cells: Toward a bifacial device

2018 ◽  
Vol 186 ◽  
pp. 227-235 ◽  
Author(s):  
Kamala Khanal Subedi ◽  
Ebin Bastola ◽  
Indra Subedi ◽  
Zhaoning Song ◽  
Khagendra P. Bhandari ◽  
...  
Keyword(s):  
Thin Film ◽  
Solar Cells ◽  
Back Contact ◽  
Cdte Solar Cells

scholarly journals Properties of Arsenic–Doped ZnTe Thin Films as a Back Contact for CdTe Solar Cells

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3706 ◽  
Author(s):  
Ochai Oklobia ◽  
Giray Kartopu ◽  
Stuart J. C. Irvine
Keyword(s):  
Thin Films ◽  
Solar Cells ◽  
Open Circuit ◽  
Activation Process ◽  
Back Contact ◽  
Contact Activation ◽  
Doping Density ◽  
Cdte Solar Cells ◽  
Absorber Doping ◽  
P Type

As-doped polycrystalline ZnTe layers grown by metalorganic chemical vapor deposition (MOCVD) have been investigated as a back contact for CdTe solar cells. While undoped ZnTe films were essentially insulating, the doped layers showed significant rise in conductivity with increasing As concentration. High p-type carrier densities up 4.5 × 1018 cm−3 was measured by the Hall-effect in heavily doped ZnTe:As films, displaying electrical properties comparable to epitaxial ZnTe single crystalline thin films in the literature. Device incorporation with as-deposited ZnTe:As yielded lower photovoltaic (PV) performance compared to reference devices, due to losses in the open-circuit potential (VOC) and fill factor (FF) related to reducing p-type doping density (NA) in the absorber layer. Some minor recovery observed in absorber doping following a Cl-free post–ZnTe:As deposition anneal in hydrogen at 420 °C contributed to a slight improvement in VOC and NA, highlighting the significance of back contact activation. A mild CdCl2 activation process on the ZnTe:As back contact layer via a sacrificial CdS cap layer has been assessed to suppress Zn losses, which occur in the case of standard CdCl2 anneal treatments (CHT) via formation of volatile ZnCl2. The CdS sacrificial cap was effective in minimising the Zn loss. Compared to untreated and non-capped, mild CHT processed ZnTe:As back contacted devices, mild CHT with a CdS barrier showed the highest recovery in absorber doping and an ~10 mV gain in VOC, with the best cell efficiency approaching the baseline devices.

Development of Cu‐doped ZnTe as a back‐contact interface layer for thin‐film CdS/CdTe solar cells

1996 ◽  
Vol 14 (3) ◽  
pp. 806-812 ◽  
Author(s):  
T. A. Gessert ◽  
A. R. Mason ◽  
P. Sheldon ◽  
A. B. Swartzlander ◽  
D. Niles ◽  
...  
Keyword(s):  
Thin Film ◽  
Solar Cells ◽  
Interface Layer ◽  
Back Contact ◽  
Contact Interface ◽  
Cdte Solar Cells

scholarly journals Investigation of Thin Film Solar Cells on CdS/CdTe Base with Different Back Contacts

2010 ◽  
Vol 74 ◽  
pp. 119-123
Author(s):  
G. Khrypunov ◽  
A. Meriuts ◽  
H. Klochko ◽  
T. Shelest ◽  
A. Khrypunova
Keyword(s):  
Thin Film ◽  
Solar Cells ◽  
Potential Barrier ◽  
Negative Impact ◽  
Boundary Surface ◽  
Base Layer ◽  
Wave Radiation ◽  
Back Contact ◽  
Recombination Mechanism ◽  
Cdte Solar Cells

The peculiarities of photo-electric processes in thin film CdS/CdTe solar cells (SC) with different back electrodes (Cu/Au, ITO, Cu/ITO) have been studied. As it was established by capacitance – voltage (C – V) characteristics, the potential barrier heights for CdTe/Cu/Au and CdTe/ITO were 0.3 eV and 2.2 eV, respectively. The concentrations of charge carriers near back contact consisted 91020 m–3 and 21021 m–3, respectively. A high carrier concentration and high potential barrier of the ITO back contact caused the tunnel – recombination mechanism of the charge transport. The investigations of CdS/CdTe/ITO SC spectral photosensitivity testify a negative impact of the developed grain-boundary surface of the base layer on the processes of diffusion and separation of non-equilibrium current carriers generated by short-wave radiation. It is shown that the deposition of Cu nanolayer before the deposition of ITO films give stable efficiency 10 % for bifacial CdS/CdTe solar cells.

MoO3 back contact for CuInSe2-based thin film solar cells

2013 ◽  
Vol 1538 ◽  
pp. 173-178 ◽  
Author(s):  
Hamed Simchi ◽  
Brian E. McCandless ◽  
T. Meng ◽  
Jonathan H. Boyle ◽  
William N. Shafarman
Keyword(s):  
Thin Film ◽  
Solar Cells ◽  
Forward Bias ◽  
Rf Sputtering ◽  
Optical Transmittance ◽  
Thin Film Solar Cells ◽  
Potential Candidate ◽  
Back Contact ◽  
Valence Bands ◽  
Diode Behavior

ABSTRACTMoO3 films with a high work function (5.5 eV), high transparency, and a wide bandgap (3.0 - 3.4 eV) are a potential candidate for the primary back contact of Cu(InGa)Se2 thin film solar cells. This may be advantageous to form ohmic contact in superstrate devices where the back contact will be deposited after the Cu(InGa)Se2 layer and MoSe2 layer doesn’t form during Cu(InGa)Se2 deposition. In addition, the MoO3 may be incorporated in a transparent back contact in tandem or bifacial cells. In this study, MoO3 films for use as a back contact for Cu(In,Ga)Se2 thin film solar cells were prepared by reactive rf sputtering with O2/(O2+Ar) = 35%. The effect of post processing on the structural properties of the deposited films were investigated using x-ray diffraction and scanning electron microscopy. Annealing resulted in crystallization of the films to the α-MoO3 phases at 400°C. Increasing the oxygen partial pressure had no significant effect on optical transmittance of the films, and bandgaps in the range of 2.6-2.9 eV and 3.1-3.4 eV were obtained for the as deposited and annealed films, respectively. Cu(In,Ga)Se2 thin film solar cells prepared using an as-deposited Mo-MoO3 back contact yielded an efficiency of >14% with VOC = 647 (mV), JSC = 28.4 (mA), and FF. = 78.1%. Cells with ITO-MoO3 back contact showed an efficiency of ∼12% with VOC = 642 (mV), JSC = 26.8 (mA), and FF. = 69.2%. The efficiency of cells with an annealed MoO3 back contact was limited to 4%, showing a blocking diode behavior in the forward bias J-V curve. This may be caused by the presence of a barrier between the valence bands of the Cu(In,Ga)Se2 and MoO3, due to the higher bandgap of the annealed MoO3 films. SEM cross section studies showed uniform coverage of the as-deposited MoO3 layer and formation of voids for the annealed MoO3 film. Structural orientation of the Cu(In,Ga)Se2 absorber layer was also altered by the MoO3 film and less-oriented films were observed for either cases.

Application of bromide-iodide lead perovskite thin film as a copper-free back contact layer for CdTe solar cells

Solar Energy ◽  
2021 ◽  
Vol 230 ◽  
pp. 832-842
Author(s):  
Biao Zhou ◽  
Fan Zhang ◽  
Junlin Zhang ◽  
Xiutao Yang ◽  
Kelin Li ◽  
...  
Keyword(s):  
Thin Film ◽  
Solar Cells ◽  
Contact Layer ◽  
Back Contact ◽  
Cdte Solar Cells

Fabrication of p-type SrCuSeF/n-type In2O3:Sn bilayer ohmic tunnel junction and its application to the back contact of CdS/CdTe solar cells

2017 ◽  
Vol 56 (8S2) ◽  
pp. 08MC18 ◽  
Author(s):  
Shuya Kitabayashi ◽  
Yasuyoshi Shiina ◽  
Ayuki Murata ◽  
Tamotsu Okamoto ◽  
Takahiro Wada
Keyword(s):  
Solar Cells ◽  
Tunnel Junction ◽  
Back Contact ◽  
Cdte Solar Cells ◽  
P Type

MoOx as an Efficient and Stable Back Contact Buffer for Thin Film CdTe Solar Cells

2012 ◽  
Vol 1447 ◽  
Author(s):  
Hao Lin ◽  
Wei Xia ◽  
Hsiang N. Wu ◽  
Ching W. Tang ◽  
Irfan Irfan ◽  
...  
Keyword(s):  
Thin Film ◽  
Solar Cells ◽  
Work Function ◽  
High Efficiency ◽  
Surface Cleaning ◽  
Back Contact ◽  
Metal Electrodes ◽  
Low Resistance ◽  
Cdte Solar Cells ◽  
Cell Stability

ABSTRACTA low-resistance back contact for n-CdS/p-CdTe solar cells has been developed, which utilizes a thermally evaporated MoOx thin film as the buffer layer between the p-CdTe and the back electrode. The low-resistance behavior of back contact is attributed to the high work function of MoOx, which reportedly is as high as 6.8 eV, and thus adequately matches that of p-CdTe. With MoOx as the buffer, a variety of common metals, even those with a low work function such as Al, have been found to be useful as the electrode in forming the back contact. Other advantages of the MoOx buffer include dry application by vacuum deposition, and thus it is particularly suitable for the fabrication of ultra-thin CdTe solar cells without introducing additional shorting defects. Surface cleaning of CdTe films prior to MoOx deposition has also been studied. The cell stability has been evaluated through thermal annealing tests. Thermal degradation has been explained in terms of oxidation of the metal electrodes. CdTe cells with high efficiency and good stability have been demonstrated with MoOx as the back contact buffer and Ni as the electrode.

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