Puvaneswaran Chelvanathan

Prospects of Cu 2 ZnSnS 4 (CZTS) solar cells from numerical analysis

In the rapid growth of thin film solar cells, Cu2ZnSnS4 (CZTS) poses to be a potential and alternative absorber layer of CIGS based cells. Besides solving the scarcity issue of rare materials like In or Ga in CIGS based solar cells, the CZTS based cells do not contain any toxic material and can lead to produce nontoxic thin film solar cells with excellent optical properties. In this work, absorber layer parameters have been studied by Solar Cell Capacitance Simulator (SCAPS) in terms of CZTS layer thickness and band gap to find out the optimum electrical performance. A promising result has been achieved with an efficiency of 7.55 % (with Voc = 0.5136 V, Jsc = 30.83 mA/cm2 and fill factor = 47.65 %) by using CZTS/CdS structure. It has also been found that the high efficiency of CZTS absorber layer thickness lies between 1 and 2.2 µm. This result can be explained in the practical work as non-stoichiometric composition of CZTS may result in lower efficiency of the solar cells. Quantum efficiency is almost 80% in the region of 350–500 nm, due to less absorption of light in the buffer layer. In addition, it is revealed that the highest efficiency cell can be achieved with the In2S3 buffer layer band gap of 2.74–2.90 eV. The study suggests that the proposed solar cell can be widely exploited in response to the fabrication of high efficiency thin film photovoltaic devices.

Effects of Transition Metal Dichalcogenide Molybdenum Disulfide Layer Formation in Copper–Zinc–Tin–Sulfur Solar Cells from Numerical Analysis

This study demonstrates the effects of transition metal dichalcogenide, MoS2 layer formation in between the copper–zinc–tin–sulphide (CZTS) absorber layer and Mo back contact from theoretical study and numerical modeling. The objective of this study is to elucidate the effects of n or p type MoS2 on the overall CZTS solar cell performance. Energy band line-up of Mo/MoS2/CZTS interface is analyzed to elucidate the interface properties. It is found out that p-MoS2 layer in CZTS solar cell induces the same adventitious effect as p-MoSe2 in CIGS solar cell. However, n-MoS2 layer has detrimental effect on the CZTS solar cell by creating an additional back contact diode with p-CZTS layer and an ohmic contact with Mo layer. Thickness, bandgap energy and carrier concentration of n-MoS2 all have been varied in the numerical simulation to observe its effects on the cell performance parameters. The results from numerical simulation show that MoS2 layer as thin as 50 nm is sufficient enough to induce adverse effect on the solar cell performance. This could be caused by the increase in series resistance of the solar cell as n-type MoS2 would inhibit hole current into Mo back contact due to the hole barrier between n-type MoS2 and Mo back contact. The increase in MoS2 bandgap and carrier concentration also results in detrimental effect to the performance of the cell mainly due to the possibility of electrons to drift towards the back contact and recombine.

Physical and optical properties of In 2 S 3 thin films deposited by thermal evaporation technique for CIGS solar cells

Indium sulphide is an promising buffer material with higher bandgap for CIGS solar cells. Promising results on the optical properties and morphology of deposited InxSy were found. In2S3 thin films were deposited onto glass substrates using thermal evaporation technique. Indium (In) and sulphur (S) powder were evaporated with different In/S ratio, where the stoichiometry and non-stoichiometry composition of InxSy influenced the optical bandgap and surface morphology. The films were structurally and optically characterized by X-ray diffraction, atomic force microscopy and UV measurements. It has been found that, the optical direct bandgap varied from 2.3 eV to 2.5 eV with the different composition ratio of InxSy. The X-ray diffraction data shows that the films have cubic ß-In2S3 structure onto the glass substrates. AFM images illustrate the surfaces quite smooth and uniform with a low surface roughness. These results can be explained in the practical work as non-stoichiometric composition of indium sulphide may result in different band gaps. Hence, a specific stoichiometric composition which results in the highest band gap is desirable to achieve high efficiency InxSy-CIGS solar cell. This is due to the lesser photon loss in the buffer layer as the light passes into the absorber layer. From the fabrication results, numerous influences of In2S3 buffer layer are investigated that can be implemented to the fabrication of high efficiency CIGS solar cells.

Effects of sulfurization temperature on Cu2ZnSnS4 thin film deposited by single source thermal evaporation method

In this study, the effects of sulfurization temperature on the properties of thermally evaporated Cu2ZnSnS4 (CZTS) thin films were investigated. Molybdenum (Mo) coated soda lime glass (SLG) was used as substrates and stoichiometric CZTS powder (99.95%) was used as the source material. XRD patterns showed that CZTS were formed with preferential orientations of (112) > (220) > (312) for all the investigated films. The intensity of (112) peak is found increasing until a certain temperature indicating that the highest degree of crystallinity is achieved together with secondary phases such as ZnS and SnS. It was confirmed by raman shift at 338 cm−1 from Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM) results showed a trend for surface roughness as well as morphology. From Hall effect measurement, all deposited films exhibited p-type conductivity. From UV–vis spectroscopy measurement, the optical band gap of all the films are found in the range of potential absorbers for CZTS based thin film solar cells.

Postdeposition Annealing Effect on Cu2ZnSnS4 Thin Films Grown at Different Substrate Temperature

Cu2ZnSnS4 (CZTS) thin films were deposited on top of Molybdenum (Mo) coated soda lime glass (SLG) substrates using a single target rf magnetron sputtering technique. The sputtering parameters such as base pressure, working pressure, rf power, argon (Ar) gas flow rate, and deposition time were kept consistent throughout the experiment. The effect of different substrate temperatures, for example, room temperature (RT), 300°C, 350°C, 370°C, 400°C, and 450°C, was analyzed by studying their structural, electrical, and optical properties. As-sputtered films were then annealed at 460°C. X-ray diffraction (XRD) measurement revealed the structure to be kesterite with peak of (112) plane in both annealed and as-sputtered CZTS thin films. The crystallinity of the films improved with the increasing substrate temperature until 370°C. Secondary phases of MoS2, , , , and Cu6MoSnS8 (hemusite) were also observed in the annealed CZTS films. Scanning electron microscopy (SEM) shows crystallite size of deposited CZTS thin film to be proportionally related to deposition temperature. The highest surface roughness of 67.318 nm is observed by atomic force microscopy (AFM). The conductivity type of the films was found to be p-type by Hall effect measurement system.

Effect of p-type transition metal dichalcogenide molybdenum ditelluride (p-MoTe 2 ) layer formation in Cadmium Telluride solar cells from numerical analysis

In this paper, we have investigated the effects of transition metal dichalcogenide namely Molybdenum ditelluride (MoTe2) layer formation in between Cadmium Telluride (CdTe) absorber layer and Mo back contact from numerical modeling. The main purpose was to investigate the possible effects of p-type MoTe2 in CdTe thin film solar cell. Energy band line-up in the vicinity of Mo/MoTe2/CdTe interface is investigated to explain the interface properties in terms of various parameters. It was found that p-type MoTe2 has some effects to the performance of CdTe thin film solar cells. Thickness, bandgap energy and carrier concentration of p-MoTe2 all have been varied in the numerical simulation to observe its effects on the cell performance. It was found that when thickness of MoTe2 is less than 20 nm, the cell efficiency decreases, which may be due to the shunting caused by the thinner p-MoTe2. Furthermore, the increase in MoTe2 bandgap results in unfavorable effect to the performance of the cell mainly due to the possibility of electrons to drift towards the back contact and recombination. The increase of the carrier concentration improves the cell performance. This could be attributed to the less recombination of electrons as well as less built in potential (Vbi) at MoTe2/CdTe junction.

Solar Photovoltaic Technologies: From Inception Toward the Most Reliable Energy Resource

The ever-increasing global energy needs due to continual population growth, imminent depletion of fossil fuels, as well as mitigating environmental pollutions around the globe have compelled mankind to search for alternatives in recent years. Among many known alternatives, solar photovoltaic (PV) technology has undoubtedly proven itself worth as one of the mainstream renewable energy resources for its various merits. Solar photovoltaic technology is capable to fit into any requirements with freedom in scalability from milli-watt to almost giga-watt range of demand and response. In years, solar PV technology has shown its inherent potential with versatility in material usage, diversified capability in energy production, as well as sustainability with minimal or almost no adverse environmental effect. This chapter will present the chronological history of the most potential solar PV technologies from the discovery of the science as “photovoltaic PV effect” through the journey of the technological development toward becoming the most reliable energy resource of the near future.

Structural and electrical characteristics of room temperature sputtered ZnO

Thin films of ZnO were deposited on cleaned soda lime glass substrates by using RF magnetron sputtering technique for deposition time of 20mins, 40mins, 60mins, 80mins and 100mins at room temperature. The structural and electrical properties of ZnO thin films were obtained from X-ray diffraction (XRD), Atomic force microscopy (AFM) and Hall Effect measurement. XRD results confirm the presence of (002) crystal orientation of ZnO and improvement of grain size was observed for films with higher deposition time. The average and the R.M.S roughness have been measured from the AFM images and the Hall Effect measurement confirms the carrier concentration, resistivity and mobility. Hall Effect data revealed that the mobility of the carriers of ZnO thin films increased with higher deposition time.

Effects on crystal structure of CZTS thin films owing to deionized water and sulfurization treatment

To condense the cost and increase the production, using abundantly obtainable non-toxic elements, Cu2ZnSnS4 (CZTS) seem to be a strong contender among the photovoltaic thin film technologies. Cu2ZnSnS4 thin films were fabricated by RF magnetron sputtering system. CZTS were sputtered on Molybdenum (Mo) coated soda lime glass (SLG) using a single target sputtering technique. The sputtering parameters (base pressure, working pressure, Argon (Ar) flow rate, RF power and sputtering time) were kept same for all three types of films. For sulfurization, the temperature used was 500 °C. Finally, As-deposited film was immersed in DIW before undergoing identical sulfurization profile. As-deposited film (Sample A), sulfurized films (Sample B) and sulfurized plus DIW treated (Sample C) were compared in terms of their structural properties by means of X-Ray Diffraction (XRD) measurement and Atomic Force Microscopy (AFM). Sample B and C showed peak of (1 1 2) planes of CZTS which are characteristics of stannite structur...

Effect of substrate temperature on the growth of CZTS thin films by RF magnetron sputtering

Cu2ZnSnS4 thin films have been deposited using a single target sputtering technique. Molybdenum coated soda lime glass has been used as substrates. The effects of substrate temperature variation are the main motive of this work. Growth temperature ranging from 300°C to 450°C was used as different substrate temperature whereas all other sputtering parameters remained same. A comparative study of electrical, optical and structural properties of these films was carried out by means of Hall, XRD, AFM and UV-Vis spectrometry. From the Atomic Force Microscopy (AFM), it was witnessed that until the substrate temperature was raised to 370°C the grain size of the films were increasing. But at 400°C and 450°C substrate temperature the grain size started decreasing. For all the films, X-Ray Diffraction measurement (XRD) showed the peaks of (2 2 0) and (1 1 2) planes of CZTS which are characteristics of stannite structure. To check the conductivity type of the films, Hall Effect Measurement System was used and it ensued p-type.