Influence of substrate temperature on physical properties of sprayed Zn0.85Mn0.15O films

L. Raja Mohan Reddy,P. Prathap,K.T. Ramakrishna Reddy 한국물리학회 2009 Current Applied Physics Vol.9 No.3

Zn1-xMnxO thin films have been synthesized by chemical spray pyrolysis at different substrate temperatures in the range, 250–450 ℃ for a manganese composition, x = 15%, on corning 7059 glass substrates. The as-grown layers were characterized to evaluate their chemical and physical behaviour with substrate temperature. The change of dopant level in ZnO films with substrate temperature was analysed using X-ray photoelectron spectroscope measurements. The X-ray diffraction studies revealed that all the films were strongly oriented along the (002) orientation that correspond to the hexagonal wurtzite structure. The crystalline quality of the layers increased with the increase of substrate temperature up to 400 ℃ and decreased thereafter. The crystallite size of the films varied in the range, 14–24 nm. The surface morphological studies were carried out using atomic force microscope and the layers showed a lower surface roughness of 4.1 nm. The optical band gap of the films was ~3.35 eV and the electrical resistivity was found to be high, ~104Ωcm. The films deposited at higher temperatures (>350 ℃) showed ferromagnetic behaviour at 10 K. Zn1-xMnxO thin films have been synthesized by chemical spray pyrolysis at different substrate temperatures in the range, 250–450 ℃ for a manganese composition, x = 15%, on corning 7059 glass substrates. The as-grown layers were characterized to evaluate their chemical and physical behaviour with substrate temperature. The change of dopant level in ZnO films with substrate temperature was analysed using X-ray photoelectron spectroscope measurements. The X-ray diffraction studies revealed that all the films were strongly oriented along the (002) orientation that correspond to the hexagonal wurtzite structure. The crystalline quality of the layers increased with the increase of substrate temperature up to 400 ℃ and decreased thereafter. The crystallite size of the films varied in the range, 14–24 nm. The surface morphological studies were carried out using atomic force microscope and the layers showed a lower surface roughness of 4.1 nm. The optical band gap of the films was ~3.35 eV and the electrical resistivity was found to be high, ~104Ωcm. The films deposited at higher temperatures (>350 ℃) showed ferromagnetic behaviour at 10 K.

Al-doped ZnS layers synthesized by solution growth method

K. Nagamani,N. Revathi,P. Prathap,Y. Lingappa,K.T. Ramakrishna Reddy 한국물리학회 2012 Current Applied Physics Vol.12 No.2

ZnS is one of the potential candidates as a window/buffer layer for solar photovoltaic applications. Aldoped ZnS nanocrystalline films were grown by a simple and economic process, chemical solution growth method. The layers were prepared for different Al-dopant concentrations that vary in the range, 0e10 at. %. The effect of Al-doping on the composition, structure, optical, electrical and photoluminescence properties of the synthesized layers was determined using appropriate techniques. The elemental composition of a typical sample with 6 at. % ‘Al’ in ZnS was Zn ¼ 44.9 at. %, S ¼ 49.8 at. % and Al ¼ 5.3 at. %. The films were nanocrystalline in nature and showed (111) plane of ZnS as the preferred orientation for all the doping concentrations. The layers with 6 at. % of Al showed a crystallite size of w9 nm. The FTIR studies confirmed the presence of ZnS in the layers. The layers showed an average transmittance of w75% in the visible region. The change of photoluminescence behaviour with dopant concentration was also studied. The electrical resistivity was considerably decreased from 107 Ucm to 103 Ucm with Al-doping. The detailed analysis of results will be presented and discussed.

Determination of the Minority Carrier Diffusion Length of SnS Using Electro-Optical Measurements

K. T. Ramakrishna Reddy,P. A. Nwofe,R. W. Miles 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.3

The minority carrier diffusion length of the “absorber layer” in a solar cell is generally accepted to be one of the most important parameters that govern the performance of a solar cell device. In this work, thin films of SnS have been thermally evaporated onto cadmium sulphide/indium tin oxide/glass substrates, to fabricate heterojunction solar cell devices. The minority carrier diffusion length was determined for the first time for SnS layers using spectral response measurements in conjunction with optical absorption coefficient versus wavelength measurements. The minority carrier diffusion length was determined to be in the range 0.18 -0.23 μm for the SnS/CdS devices investigated in this work.

Development of sulphurized SnS thin film solar cells

MINNAM REDDY VASUDEVA REDDY,Sreedevi Gedi,박진호,Miles R.W,Ramakrishna Reddy K.T 한국물리학회 2015 Current Applied Physics Vol.15 No.5

Thin films of tin sulphide (SnS) have been grown by sulphurization of sputtered tin precursor layers in a closed chamber. The effect of sulphurization temperature (Ts) that varied in the range of 150-450 ℃ for a fixed sulphurization time of 120 min on SnS film was studied through various characterization techniques. X-ray photoelectron spectroscopy analysis demonstrated the transformation of metallic tin layers into SnS single phase for Ts between 300 ℃ and 350 ℃. The X-ray diffraction measurements indicated that all the grown films had the (111) crystal plane as the preferred orientation and exhibited orthorhombic crystal structure. Raman analysis showed modes at 95 cm-1, 189 cm-1 and 218 cm-1 are related to the Ag mode of SnS. AFM images revealed a granular change in the grain growth with the increase of Ts. The optical energy band gap values were estimated using the transmittance spectra and found to be varied from 1.2 eV to 1.6 eV with Ts. The Hall effect measurements showed that all the films were p-type conducting nature and the layers grown at 350 ℃ showed a low electrical resistivity of 64 Ω-cm, a net carrier concentration of 2 × 1016 cm3 and mobility of 41 cm2 V-1 s-1. With the use of sprayed Zn0.76Mg0.24O as a buffer layer and the sputtered ZnO:Al as window layer, the SnS based thin film solar cell was developed that showed a conversion efficiency of 2.02%.

Effect of sulfurization temperature on the efficiency of SnS solar cells fabricated by sulfurization of sputtered tin precursor layers using effusion cell evaporation

Minnam Reddy, Vasudeva Reddy,Cho, Haeyun,Gedi, Sreedevi,Reddy, K.T. Ramakrishna,Kim, Woo Kyoung,Park, Chinho Elsevier 2019 Journal of Alloys and Compounds Vol.806 No.-

<P><B>Abstract</B></P> <P>Earth-abundant tin monosulfide (SnS) thin films have attracted considerable interest for eco-friendly and low-cost thin film solar cells. However, less attention has been paid on the fabrication of SnS solar cell by the industrial processes. In view of that the current study aimed to fabricate the SnS solar cells via two-stage (sputtering + sulfurization) industrial process. For the preparation of SnS thin films, first tin metallic precursor layers were deposited by DC sputtering and then sulfurized using the rapid thermal effusion cell evaporation process. The effect of sulfurization temperature on the physical properties of SnS thin films and the efficiency of SnS solar cells was examined. Formation of the single phase SnS thin films was confirmed when the tin metallic precursor layers sulfurized in the range of 450–470 °C, whereas secondary phases of Sn, SnS<SUB>2</SUB>, and Sn<SUB>2</SUB>S<SUB>3</SUB> were noticed at the sulfurization temperature lower than 450 °C and re-evaporation of deposited SnS thin films was observed at the sulfurization temperature higher than 470 °C. Solar cell fabricated with SnS absorber sulfurized at a temperature of 470 °C showed the conversion efficiency of ∼ 2.3%. The causes for lower efficiency of these solar cells were recombination in the SnS absorber and non-uniform compositional distribution of Cd, S and Sn as a function of depth in the CdS/SnS/Mo structure.</P> <P><B>Highlights</B></P> <P> <UL> <LI> SnS films were grown via sulfurization using effusion cell evaporation method. </LI> <LI> Effect of sulfurization temperature on the efficiency of SnS solar cells was examined. </LI> <LI> A high efficiency of ∼2.3% for SnS solar cells was achieved at 470 °C. </LI> <LI> The causes for lower efficiency of these solar cells were investigated. </LI> </UL> </P>

Effect of annealing on the physical properties of thermally evaporated In2S3 thin films

S. Rasool,K. Saritha,K.T. Ramakrishna Reddy,M.S. Tivanov,A.V. Trofimova,S.E. Tikoto,L. Bychto,A. Patryn,M. Maliński,V.F. Gremenok 한국물리학회 2019 Current Applied Physics Vol.19 No.2

The structural, compositional, morphological and optical properties of In2S3 thin films, prepared by thermal evaporation technique and annealed in sulfur ambient at different temperatures have been investigated. The grazing incident X-ray diffraction patterns have indicated polycrystalline form and predominantly cubic structure of annealed In2S3 films. The scanning electron microscopy revealed textured surface with uniformly distributed grains and the grain size increased with increase of annealing temperature. The optical parameters of the films have been determined using conventional transmission and reflection spectra as well as from surface photovoltage measurements.

Vibrational and Morphological Studies of Wet Deposited SnS Films for PV Applications

G. Sreedevi,M.Vasudeva Reddy,K.T.Ramakrishna Reddy,Chan-Wook Jeon 한국신재생에너지학회 2015 한국신재생에너지학회 학술대회논문집 Vol.2015 No.6

Growth and characterization of indium oxide films

P. Prathap,G. Gowri Devi,Y.P.V. Subbaiah,K.T. Ramakrishna Reddy,V. Ganesan 한국물리학회 2008 Current Applied Physics Vol.8 No.2

In2O3 250450.C. The structural and morphological properties of the as-deposited lms were studied using X-ray diractometer and scanningelectron microscope as well as atomic force microscope, respectively. The lms formed at a temperature of 400.C showed body-centeredcubic structure with a strong (22) orientation. The structural parameters such as the crystallite size, lattice strain and texture coecientof the lms were also calculated. The lms deposited at a temperature of 400.C showed an optical transmittance of >85% in the visibleregion. The change of resistivity, mobility, carrier concentration and activation energies with the deposition temperature was studied.The highest gure of merit for the layers grown at 400℃ was 1.09x10-³Ω-¹.

Preparation and characterization of sprayed In₂O₃:Mo films

Prathap, P.,Gowri Devi, G.,Subbaiah, Y. P. V.,Ganesan, V.,Ramakrishna Reddy, K. T.,Yi, J. WILEY-VCH Verlag 2008 Physica status solidi. PSS. A, Applications and ma Vol.205 No.8

<P>Transparent conducting oxides (TCO) play a major role in the area of thin film photovoltaics, flat panel displays, organic light emitting diodes and other optoelectronic devices. In order to improve the performance of a device, the TCO should have good optical transmittance as well as conductivity. In the present study, In<SUB>2</SUB>O<SUB>3</SUB>:Mo films have been grown by an economic and simple spray pyrolysis method with different molybdenum doping concentrations that vary in the range, 0–12 at% at a substrate temperature of 400 °C. The structural and morphological, electrical and optical behaviour of the as-grown layers were studied. All the deposited layers showed a body-centered cubic structure with a strong (222) orientation. In<SUB>2</SUB>O<SUB>3</SUB>:Mo films grown with Mo-concentration of 6.0 at% had the maximum grain size of 90 nm. The average optical transmittance of the films was >85% in the visible region. The change of grain size, electrical resistivity, carrier mobility and density, optical band gap and figure of merit with doping concentration was reported and discussed. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>

A Facile and TGA Free Hydrothermal Synthesis of SnS Nanoparticles

Y. P. Venkata Subbaiah,Narayana Thota,M. Raghavender,Y. P. Venkata Subbaiah,G. Hema Chandra,K.T. Ramakrishna Reddy 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.10

"In this paper, we employed a simple and cost-effective thioglycolic acid (TGA) free hydrothermal method, based on thiourea hydrolysis of stannous chloride dihydrate [SnCl2 · 2H2O] at 160 ℃ – 190 ℃ for 6 h, for the synthesis of SnS nanoparticles. The effect of hydrothermal autoclave reaction temperature on various properties of SnS nanoparticles have been examined at length using X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy attached with EDAX (FE-SEM), transmission electron microscopy (TEM) and ultraviolet-visible (UV-Vis) spectroscopy. The results suggest that the crystallization of orthorhombic SnS nanoparticles, with size varying from 3 nm to 5 nm, formed at RT = 160 ℃. Further, the formation of SnS phase was confirmed by an IR Sn-S characteristic bands around 2350 cm -1, 1041 cm -1 and 570 cm -1, and four distinguished Raman peaks at 95 cm -1, 160 cm -1, 189 cm -1 and 220 cm -1. The mechanism for the formation of SnS nanoparticles have been proposed and discussed. The SnS nanoparticles have exhibited reaction temperature dependent morphological features like nanoflowers, nanoflakes, spherical nanoparticles and nanogranules. The absorbance studies indicated both strong direct and weak indirect allowed transitions for SnS nanoparticles and the associated band gaps were found to be 1.5 eV and 1.19 eV, respectively. The dual band gap combination of SnS would favor strong direct absorption of carriers and improved minority carrier life time due to indirect nature, which means the grown particles are suitable for ideal absorber material for solar cell applications. "