Papers by Isuru Lakmal
Journal of Materials Science: Materials in Electronics
Journal of Materials Science: Materials in Electronics
Journal of Materials Science: Materials in Electronics
Springer Proceedings in Energy, 2022
Nanomaterials
This study focuses on fabricating efficient CdS/CdTe thin-film solar cells with thermally evapora... more This study focuses on fabricating efficient CdS/CdTe thin-film solar cells with thermally evaporated cuprous iodide (CuI) as hole-transporting material (HTM) by replacing Cu back contact in conventional CdS/CdTe solar cells to avoid Cu diffusion. In this study, a simple thermal evaporation method was used for the CuI deposition. The current-voltage characteristic of devices with CuI films of thickness 5 nm to 30 nm was examined under illuminations of 100 mW/cm2 (1 sun) with an Air Mass (AM) of 1.5 filter. A CdS/CdTe solar cell device with thermally evaporated CuI/Au showed power conversion efficiency (PCE) of 6.92% with JSC, VOC, and FF of 21.98 mA/cm2, 0.64 V, and 0.49 under optimized fabrication conditions. Moreover, stability studies show that fabricated CdS/CdTe thin-film solar cells with CuI hole-transporters have better stability than CdS/CdTe thin-film solar cells with Cu/Au back contacts. The significant increase in FF and, hence, PCE, and the stability of CdS/CdTe solar cel...
Materials Science and Engineering: B
Abstract CdS thin films were deposited by vacuum thermal evaporation technique on Fluorine-doped ... more Abstract CdS thin films were deposited by vacuum thermal evaporation technique on Fluorine-doped Tin Oxide glass substrates at different substrate temperatures ranging from 50 to 250 °C. Post deposition heat-treated thin films were characterized for optical, structural, morphological and electrical properties to study the dependence substrate temperature. The optical bandgap was found in the range of 2.42–2.46 eV. Crystallite size, microstrain, phase distribution, and lattice parameters were calculated using x-ray diffractogram profile fit, Rietveld and Pawley refinement techniques. Best electrical properties of photoelectrochemical cells were observed for the films grown at a substrate temperature of 175 °C. CdS/CdTe full cells were fabricated using thermal evaporation technique and the highest efficiency of 3.76% and highest external quantum efficiency of 70% were observed for the CdS thin film grown at a substrate temperature of 175 °C and the variation was confirmed with SCAPS-1D simulation.
Materials Science and Engineering: B, 2021
CdS thin films were deposited by vacuum thermal evaporation technique on Fluorine-doped Tin Oxide... more CdS thin films were deposited by vacuum thermal evaporation technique on Fluorine-doped Tin Oxide glass substrates at different substrate temperatures ranging from 50 to 250 • C. Post deposition heat-treated thin films were characterized for optical, structural, morphological and electrical properties to study the dependence substrate temperature. The optical bandgap was found in the range of 2.42-2.46 eV. Crystallite size, microstrain, phase distribution, and lattice parameters were calculated using x-ray diffractogram profile fit, Rietveld and Pawley refinement techniques. Best electrical properties of photoelectrochemical cells were observed for the films grown at a substrate temperature of 175 • C. CdS/CdTe full cells were fabricated using thermal evaporation technique and the highest efficiency of 3.76% and highest external quantum efficiency of 70% were observed for the CdS thin film grown at a substrate temperature of 175 • C and the variation was confirmed with SCAPS-1D simulation.
Cadmium sulfide (CdS) is a II-VI group semiconducting material which has been thoroughly investig... more Cadmium sulfide (CdS) is a II-VI group semiconducting material which has been thoroughly investigated due to its superior optical and electrical properties that can be applicable in wide range of semiconductor devices including photonic devices. Due to its direct and wide bandgap (~ 2.42 eV), it is vastly used as the window layer in heterojunction thin film solar cells. Compared to other deposition methods such as electrodeposition, spray pyrolysis, chemical bath deposition; thermal evaporation is an attractive method of deposition due to its high deposition rate, low cost of operation, low material consumption, minimum number of impurities and straight-line propagation of vapors. In the present study, CdS thin films were deposited on cleaned FTO glass substrates using thermal evaporation technique at substrate temperatures ranging from 50 to 250 °C at a pressure of 2×10 -5 torr. Deposition was carried out using CdS powder (Sigma-Aldrich, 99.995%) using an alumina boat. Deposited samples were then annealed at 300 °C for 30 minutes in vacuum (pressure of 3×10 -5 torr). Structural, optical and electrical properties of annealed CdS thin films were studied by employing X-ray diffraction, UV-Vis spectrometry, I-V measurements and capacitance vs. voltage measurements. All the electrical characterizations were carried out using a photoelectrochemical cell of (CdS/0.1 M Na2S2O3/Pt). The XRD analysis shows all the grown films are preferably oriented in the direction of (002) of hexagonal CdS. The optical band gap values were found to increase with increasing substrate temperature from 50 to 175 °C. ISC and VOC values of (CdS/0.1 M Na2S2O3/Pt) cell were also found to increase up to the substrate temperature of 175 °C. The observed highest ISC and VOC values were 37.24 µA and 314.9 mV respectively. Results indicate that the CdS thin films deposited at the substrate temperature of 175 °C has yielded the best optical and electrical properties compared to the films grown at other substrate temperatures.
Conference Presentations by Isuru Lakmal
International Conference on Applied and Pure Sciences, 2020
* Cadmium sulfide (CdS) thin films are regarded as one of the most promising materials for hetero... more * Cadmium sulfide (CdS) thin films are regarded as one of the most promising materials for heterojunction solar cells. Due to its wide bandgap (~ 2.42 eV), CdS thin films have been used as the window material together with several semiconductors such as InP, CdTe, Cu 2S, and CuInSe 2. For the future development of photonic devices based on above materials, comprehensive studies on CdS window layer throughout all aspects such as deposition technique, temperature, duration, and post-heat treatments, etc. are highly required. In this study, CdS thin films were deposited on the cleaned FTO glass substrates using vacuum thermal evaporation technique by varying the deposition duration to have different layer thicknesses. The temperature of the substrates and the chamber pressure were maintained at 175 °C and 2×10-5 torr respectively. The deposition was carried out using CdS powder (Sigma-Aldrich, 99.995%) containing in an alumina boat. Deposited samples were then annealed in vacuum (pressure 3×10-5 torr) at 300 °C for 30 minutes. The bandgap and optical transmittance of the deposited thin films were studied using UV-Visible spectrophotometry. The surface topology analysis of the deposited thin films was carried out using Atomic Force Microscopy (AFM). A photoelectrochemical cell of (CdS/0.1 mol L-1 Na 2 S 2 O 3 /Pt) was used to investigate electrical properties such as short circuit current (J SC), open circuit voltage (V OC), carrier concentration, and majority carrier type of the semiconductor with the aid of I-V measurements and Mott-Schottky measurements. The structural and crystal properties such as preferred orientation, phase distribution, crystallite size, microstrain, and lattice parameters were studied by employing the grazing incident X-ray diffraction. The calculations were done using the profile fit, Rietveld refinement, and Pawley Refinement technique. All the results revealed that there exists a correlation between the film thickness and the above-considered properties of the CdS thin film. The highest bandgap of 2.43 eV and optimum J SC and V OC of 113 µA/cm 3 and 341 mV respectively was observed for the photoelectrochemical cell made by 210 nm thick CdS thin film.
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Papers by Isuru Lakmal
Conference Presentations by Isuru Lakmal