This manuscript presents an optimization of the performances of the CISSe/CdS/ZnO structure. 12 tests were performed for each layer on thickness, gap energy and temperature using SCAPC-1D. Numerical data were compiled with the open circuit voltage, the short circuit density, the fill factor and the efficiency. The results obtained are confirmed with the measurements illustrated in the literature. The analyses indicate a progressive improvement in the performance of the structure for each test; an efficiency of 28.8 % was recorded for the CISSe layer while 30.07 % as an efficiency for CdS and 31.47 % for the absorbent layer. On the other hand, an open circuit voltage does not exceed 1.37V for the whole structure.Thus, these results are satisfied and encouraged.
Research
Improvement of CISSe / CdS / ZnO Structure Performance by SCAPS-1D.
https://doi.org/10.21203/rs.3.rs-965170/v1
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Optimization of the performance of the CISSe/CdS/ZnO layer.
Performing 12 tests on the four characteristics of each layer.
Achievement of 30.47 % efficiency for the main layer in the cell.
The development of high efficiency and low cost solar cells is one of the challenges for most manufacturers in this field. Therefore, research has accelerated to find a structure which has high energy production capacities and which depends on non-toxic materials. Semiconductors are considered to be one of the efficient and innovative solutions. These thin films have many properties such as the ability to adjust its bandgap, thickness and even the doping method. One of the most famous of semiconductors are CISSe, CdS and ZnO. These three layers have been used in the construction of many structures with great capacities, high efficiency and very encouraging cost. Copper indium sulfoselenide, CuIn(S, Se)2 is an inorganic nanocrystalline chalcogenide, Its efficiency varies between 18.08 % and 22.50 % [1], [2] depending on the role it plays in the structure. On the other hand, CdS cadmium has a bad reputation which is harmful to the environment, but recently discovered treatment methods have reduced its toxicity [3]. The ZnO layer is a main element in the fabrication of structures of photovoltaic systems, which shows an efficiency can reach up to 17.86 % [4] - [6]. Therefore, configuring a structure based on these perovskite cells will be a huge boost to the solar cell industry.
In this article, the CISSe/CdS/ZnO structure is highlighted in order to develop its performance and evaluate its efficiency. This structure where CISSe is a window layer, CdS is a conductive layer and ZnO is absorbent. A set of tests will be carried out on the thickness, the gap energy and the temperature for each layer under the effect of a radiation of 1000w/m² (see figure 1). By using the SCAPS-1D software, some analyses are carried out on current density, fill factor and voltage.
The methodology is based on performing three basic tests related to each layer. In the first step, the thickness, the gap energy (Eg) and the temperature are tested in the intervals [0.1 eV; 2 eV], [1µm; 50µm] and [300K, 350K] respectively for the CISSe layer. Data will be compiled on these fourth characteristics including Voc, Jsc, FF and efficiency(η). For an easy evaluation, these characteristics will be named according to the layer that contributed to modification. During all tests, table.1 is approved in the evaluation process. The second and third stages will be carried out following the same procedure to study the CdS and ZnO layers through different intervals which will be indicated in the continuation of this research. It should be noted that there are 9 tests carried out on the CISSe/CdS/ZnO structure.
Tab.1.Physical property of the layers used.
CISSelayer optimization
The Egof CISSe will be varied from 0.1 eV to 2 eV with a step of 1 eV. Fig.2 illustrates the results obtained for the four parameters Jsc,cisse;Voc,cisse;EFCISSe;hCISSe.
Fig.2-a ,shows the stability of the J-V characteristics between 0.1 eV and 1.0 eV for the values; Jsc,cisse = 43,57 mA/cm²;Voc,cisse = 0,843 V.After that, we noticed a sudden decreasing change of these two characteristics, then increase in their values until reaching the maximumJsc,cisse(max) = 43,58 mA/cm²;Voc,cisse(min) = 0,7597 V, with Eg,CISSe = 1.7 eV. After the characteristics know a stability in their values. In Fig.2-b we also held the same comment for the couple (EFCISSe;hCISSe) where the stability was recorded in the same period for the pair, and after that, a maximum increase has was known at the point Eg,CISSe = 1.7 eV where a higher efficiency was obtained hCISSe = 27.56 % and EFCISSe = 83.26 %. This value found will be analysed according to the thickness of the window layer.
Fig.3-a shows the evolution of the current density and the voltage as a function of the width of the Window layer. The thickness will be varied between 1μm and 50μm with a step of 1 and the Eg set in 1.7 eV of CISSe. We notice a significant increase in the couple Jsc, Voc from the start of the thickness until to the value 15μm. From this value, we notice the inflection of the two curves, but with a slight continuation of their rise until they reach maximum values Jsc,CISSe (max) = 45.35mA/cm2, Voc,CISSe (max) = 0.843 V at 20μm thickness. The results of Fig.3-b indicate a significant increase in efficiency η (%) up to the maximum value ηCISSe(max) = 30.07 % for the same thickness. On the other hand, an accelerated decrease in EFCISSe as a function of thickness. Therefore, the efficiency was improved and linked to the thickness. Finally, we can say that at 20μm with Eg,CISSe = 1.7 eV, we obtain an ideal efficiency of the CISSe window layer compared to the measurements indicated in[7], [8].
For the thickness 20μm and Eg,CISSe = 1.7 eV, Fig.4-a and Fig.4-b show the variation of the characteristics of the two pairs (Jsc,cisse;Voc,cisse) and (EFCISSe;hCISSe). Between 300K and 350K, the temperature enhances the mobility of electrons in the Se window layer; result well explained by Fig.3-a by the increase of Jsc. On the other hand, the parameters Voc,cisse;EFCISSe;hCISSe decrease to minimum values Voc,CISSe(min) = 0.843V;EFCISSe = 75.87 % ;hCISSe(min) = 28.8 %, result considered positively by comparing with the results recorded in [9], [10].
CdS layer optimization on 20μm CISSe thickness and Eg,CISSe = 1.7 eV
The second test will be carried out on the study of the buffer of the CdS layer at a temperature of 300K under the following conditions. Eg,CISSe = 1.7 eV, Eg,ZnO = 3.3 eV. The thicknesses of CISSe and ZnO will be fixed at 20 μm and 0.2 μm . Eg,CdS will be varied between 0.1 eV and 3.5 ev with a step of 0.5 eV. The results obtained are shown inFig.5.
Fig.5-a illustrates the variation of Jsc, CdS and Voc, CdS under the effect of the Eg,CdS. We notice between 0.1 eV and 1.0 eV, there is an overlap between the two curves at the level of their variation. After the value of 1 eV, the two parameters increase to a maximum value Jsc,CdS(max) = 45.35mA/cm²,Voc,CdS(max) = 0.8436V when the value of Eg,CdS>2 eV. As for Fig.5-b, it shows a quasi-agreement between the curve EFCdS and ηCdS at the level of their evolutions until they reach the constant values indicating a maximum efficiency ηCdS = 30.06 % and EFCdS = 78.87 % when the energy Eg,CdS>2 eV.
The curves of Jsc,CdS,Voc,CdS illustrated in Fig.6-a make it possible to show the effect of CdS layer thickness while setting the Eg,CdS at 2.5 eV. It shows a decrease in current density against an increase in voltage. It is noted that the same evolution is recorded on Fig.6-b while indicating a stability of the efficiency at the value ηCdS = 27.66 % with a decrease of EFCdS in the piece of value 0.1 μm.
On the temperature interval between 300K and 350K for the CdS layer, Figs 7-a and 7-b illustrate the evolution of the characteristics of this layer under the condition of new parameters such as Eg,CdS = 2.5 eV and its thickness 0.1μm. We notice the only significant increase in current density indicating a movement of the electron-holes, on the other hand there is a decrease in the other characteristics. For this test the ηCdS recorded efficiency is the order of 30 %instead of the 16 % illustred in[11]–[13].
ZnO layer optimization when the thickness of CISSe is 20μm, Eg,CISSe = 1.7 eV and the thickness of CdS is 0.1μm and Eg,CdS = 2.5 eV.
The test is taken at temperature of 300K respecting the following conditions: the thickness of CISSe is 20μm and Eg,CISSe = 1.7 eV and the thickness of CdS is 0.1μm and Eg,CdS = 2.5 eV. Figs.8-a and 8-b show the variation of the characteristics Jsc,ZnO; Voc,ZnO;EFZnO;hZnO of the main layer of the cell studied while putting the ZnO ,Eg,ZnO between 1 eV and 8 eV.
The Fig.8-a,above shows the stability of the voltage at the value 0.8436v during the variation of the Eg,ZnO . On the other hand we notice an increase in current density Jsc,ZnO up to the value 45,89 mA/cm². On the other hand, Fig.8-b indicates a decrease in duality factor and an increase in efficiency until reaching a new value ηZnO30.41 % instead of 23 % illustrated in[14], [15]
The thickness of the ZnO layer is varied between 0.001μm and 0.1μm while keeping the optimal values found to check the variation on the four variables studied. We notice in Fig.9-a a decrease in Jsc,ZnO as a function of the thickness and a stability of Voc,ZnO at the value 0.8436 V. As for Fig.9-b which notices an increase in efficiency up to a maximum value hZnO = 30,47 % by comparing with results illustrated in[16]. The factor of EFZnO has experienced a decrease of 40 %.
Figure 10 shows the action of the ZnO layer temperature variation on the characteristics of the CISSe/CdS/ZnO structure. The profile of the couples (Jsc, Voc) and (FF, n) represented in figure.10-a and figure.10-b show a significant decrease in Voc, FF and ƞ against an increase in Jsc that expresses by the fact that the heat is lost due to release of an energy in hυ form. In despite of what happened, this remains encouraging because there is a little decrease in efficiency which not exceeding 2.98 %; value compared with those reviewed by the measures illustrated in references [17] [18].
In this article, the effect of thickness, gap energy and temperature have been demonstrated on the CISSe/CdS/ZnO layers to optimize the physical characteristics of the window layer CISSe, the buffer of CdS and absorption of ZnO. Using numerical simulation on the SCPAC-1D computer code, 12 tests were performed on the three layers. The results obtained show, on the basis of these parameters such as the Thickness of CISSe of 20μm, Eg,CISSe = 1.7 eV, the thickness of CdS is 2.5μm, Eg,CdS = 1 eV, thickness of ZnO is 0.001 μm and Eg,ZnO = 4 eV and under a temperature of 300K, the improvement in the performance of the studied cell can reach 30.47 % for the absorbent layer, 30.07 % for the CdS layer and 28.8 % for the window layer. These results remain satisfactory in comparison with the most recent measurements which were carried out on the same cell.
Nomenclatures
Eg : Gap energy
FF : Fill factor
Jsc : Short circuit density.
Voc : Open circuit voltage
H : Planc concatant
SCAPS-1D: One-dimensional Solar Cell Capacitance Simulator.
Data Availability statement
The authors declare that there is no conflicts of interest regarding the publication of this paper.
Acknowledgments
This work is supported by the team renewable energy of ibn tofail university kenitra ,morocco.
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