The Research On The Preparation Of Cu-based Absorbing Layer By A Novel Green Solution Process And Its PV Device Fabrication

Cu-based absorbing layer is one of the most promising and attractive absorbermaterials for thin film solar cells due to its inherent properties. The development oftraditional vacuum process might be limited by the problems with cost andcomplicated manufacting procedure. The non-vacuum methods for the preparation ofCIGS absorbing layers have been developed rapidly these years due to its severalattractive advantages especially in large-scale manufacturing and lower cost. In thisstudy, the non-vacuum process of the Cu-based absorbing layer which is environmentfriendly and low cost and suitable for large-scale manufacturing is explored. Thispaper can be devided into three sections as follows:Part one: The preparation and characterization of CISS absorbing layer. Firstly, wepresent a new green synthesis route of the precursor solution. Cu(NO3)2·3H2O andInCl3·4H2O are choosed as the sources of copper and indium, respectively. Ethanol,1-butylamine and carbon disulfide are employed as the solvent, complexing agent andannexing agent, respectively. Meanwhile, the influence of Cu-In ratio to the CISSabsorbing layer is also studied, the best Cu-In ratio is Cu/In=0.8/1.0. Secondly, aftercompare the spin-coating and the doctor blading process, spin-coating is choosed forthe deposition of this precursor thin film. The best condition for pre-treatment is350℃for5minutes under nitrogen atmosphere. Thirdly, the selenization andsulfuration treatment is processed in the double-zone tubular furnace using solid stateselenium powder and sulfur powder as the sources of selenium and sulfur. The bestconditions for selenization and sulfuration are550℃for60minutes and550℃for20minutes. Finally, the characterization for the CISS thin film. The XRD resultsindicate that the thin film shows a single chalcopyrite structure with preferred (112)orientation. The dense big grains with micron levels are observed from the SEM. TheUV-VIS-IR spectrum curve indicates the band gap of the absorbing layer is about1.24eV,which is suitable for the fabrication of thin film solar cells.Part two: the fabrication and characterization of CZTS absorbing layer. Indium andGallium used in solar cells are replaced by Zinc and Tin in our study, which are moreabundant and lower cost. The same solvents composed of1-butylamine and carbondisulfide are used to synthesize the CZTS precursor solution. The best condition forselenization is500℃for60minutes and the best condition for sulfuration is500℃for20minutes. The thin film shows predominant CZTS phase with a single kesterite structure and the preferred (112) orientation from XRD and Raman results. The denselarge grains with about1.5um are observed from the SEM. The band gap of CZTSabsorbing layer is about1.25eV from the result of UV-VIS-IR investigation.Part three: the fabrication of the thin film solar cells. In this study, chemical bath isemployed to deposit the CdS buffer layer. The best conditions for the deposition ofCdS are70℃for20minutes. The window layers ZnO and AZO are prepared bysputtering. The best condition for this process is150W for30minutes under0.8Pa Argas pressure. The top Ag electrode is finished by the thermal evaporation. The CISSand CZTS solar cell devices had been tested. The Vocand Jscof the CISS solar cellbefore sulfuration process are270mV and33.5mA/cm2, respectively, the fill facter ofthe device is0.47and the conversion efficiency is4.16%. The Vocand Jscof the CISSsolar cell after sulfuration process are440mV and18.5mA/cm2, respectively, and thethe fill facter of the device is0.52, the conversion efficiency is4.25%.The Vocand Jscof the CZTS solar cell are310mV and26.5mA/cm2, respectively, the fill facter of thedevice is0.34and the conversion efficiency is2.7%.In conclusion, efficient CISS andCZTS thin film solar cell devices are successfully fabricate, which has importantscientific significance and potential application prospect.