Preparation and Enhancement of CdS/ZnS Thin Films for Photovoltaic Purposes

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Date
2011-06-01
Authors
Maysa Tayseer Mohammad Atatrih
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<p>Polycrystalline CdS/ZnS thin films were prepared by chemical bath deposition (CBD)technique on fluorine-doped tin oxide (FTO) coated glass substrates. Enhancement ofdeposited CdS/ZnS thin film characteristics at solid/liquid interface in photoelectrochemical(PEC) systems was investigated. Deposited CdS/Zns thin films were exposed to differenttreatment methods and different treatment methods and different experimental conditions.The films were heated to desired temperatures (300⁰C, 400⁰C) under air. Cooling of heatedfilms to room temperaturewas achieved by either slow cooling or quenching. Etching of film surface was conductedusingdilute HCI solution. The effect of such treatment on the film photoelectrochemicalcharacteristics was measured by monitoring different parameters, such as: open-circuitvoltage (Voc ), short-circuit current density (Jsc), dark current density-potential (J-V) plots,photo J-V plots, conversion efficiency (η), fill factor (FF), Scanning electron microscopy (SEM),X-ray diffraction, together with electronic absorption and photoluminescence (PL) emissionspectra.The characteristics of CdS/ZnS thin films in PEC systems were enhanced by controllingdifferent experimental conditions, controlling preheating temperatures and controllingcooling rates. The dark- and photo- current densities vs. potential plots were improved byannealing. Cell efficiency, fill factor, short-circuits current densities (Jsc) and SEM resultswere enhanced for the annealed CdS/ZnS films. The best annealing temperature for CdS/ZnSfilms was found to be 300⁰C at which the photo J-V plots and cell efficiency were improvedsignificantly. Slowly cooled electrodes from temperature 300⁰C, gave better dark and photocurrent density vs. potential plots with higher efficiency than their quenched counterparts.SEM measurements were consistent with these findings, and showed better surfaces forNano Technology(IYC-2011) 70slowly cooled CdS/ZnS thin film electrodes. Maximum values of conversion efficiencies wereobtained by slow cooling of preheated CdS/ZnS electrodes cooled from temperature 300⁰Ccompared to that of electrodes cooled from 400⁰C.The effect of coating the CdS/ZnS electrodes with MnP/polysiloxane was also studied. The(Jsc) values of coated CdS/ZnS films (with certain Zn ratios) were significantly enhanced. TheMnP/ploysilocane coating introduces a charge-transfer mediator species that enhancescurrent and electrode stability.</p>
<p>Polycrystalline CdS/ZnS thin films were prepared by chemical bath deposition (CBD)technique on fluorine-doped tin oxide (FTO) coated glass substrates. Enhancement ofdeposited CdS/ZnS thin film characteristics at solid/liquid interface in photoelectrochemical(PEC) systems was investigated. Deposited CdS/Zns thin films were exposed to differenttreatment methods and different treatment methods and different experimental conditions.The films were heated to desired temperatures (300⁰C, 400⁰C) under air. Cooling of heatedfilms to room temperaturewas achieved by either slow cooling or quenching. Etching of film surface was conductedusingdilute HCI solution. The effect of such treatment on the film photoelectrochemicalcharacteristics was measured by monitoring different parameters, such as: open-circuitvoltage (Voc ), short-circuit current density (Jsc), dark current density-potential (J-V) plots,photo J-V plots, conversion efficiency (η), fill factor (FF), Scanning electron microscopy (SEM),X-ray diffraction, together with electronic absorption and photoluminescence (PL) emissionspectra.The characteristics of CdS/ZnS thin films in PEC systems were enhanced by controllingdifferent experimental conditions, controlling preheating temperatures and controllingcooling rates. The dark- and photo- current densities vs. potential plots were improved byannealing. Cell efficiency, fill factor, short-circuits current densities (Jsc) and SEM resultswere enhanced for the annealed CdS/ZnS films. The best annealing temperature for CdS/ZnSfilms was found to be 300⁰C at which the photo J-V plots and cell efficiency were improvedsignificantly. Slowly cooled electrodes from temperature 300⁰C, gave better dark and photocurrent density vs. potential plots with higher efficiency than their quenched counterparts.SEM measurements were consistent with these findings, and showed better surfaces forNano Technology(IYC-2011) 70slowly cooled CdS/ZnS thin film electrodes. Maximum values of conversion efficiencies wereobtained by slow cooling of preheated CdS/ZnS electrodes cooled from temperature 300⁰Ccompared to that of electrodes cooled from 400⁰C.The effect of coating the CdS/ZnS electrodes with MnP/polysiloxane was also studied. The(Jsc) values of coated CdS/ZnS films (with certain Zn ratios) were significantly enhanced. TheMnP/ploysilocane coating introduces a charge-transfer mediator species that enhancescurrent and electrode stability.</p>
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