Investigation On Preparation Method And Properties Of Cu?In,Ga?Se₂ Thin Films For Solar Cells

Because of its high efficiency and strong stability,Cu?In,Ga?Se₂?CIGS?thin film solar cell is one of the most potential technologies of thin film solar cells.The preparation of CIGS absorber is the key problem in the research of CIGS solar cell,while the manufacturing cost is the key factor for the wide application of solar cells.This dissertation focuses on the low cost preparation method of CIGS thin films,including magnetron sputtering and chemical solution deposition,and investigates the relationship between processing parameters and properties of CIGS thin film and solar cell device.The main research contents and innovation points of this dissertation are as follows.1.This dissertation reports the Raman spectra and electrical analysis of Se-deficient Cu?In,Ga?Se2?CIGS?films with various Cu contents.These films were deposited by two-step process consisting of sputtering of metallic precursor and subsequent selenization.Electrical measurements show the change of main carrier source as well as the transformation of conduction type with varying Cu content.Comprehensive analysis of Raman spectra and electrical measurements qualitatively explains the relationship between electrical properties and Cu contents.Based on this relationship,the optimal range of Cu/?Ga+In?for Se-deficient CIGS solar cells is identified as 0.875–0.925,which is smaller than that for Se-sufficient CIGS solar cells due to the presence of Se vacancies.As Raman spectroscopy is nondestructive and resistivity measurement is easy to take,the results are useful in the estimation of device performance at early process stages.2.This dissertation reports the influence of different Cu contents on the microstructure of CIGS thin films.The CIGS thin films were grown on Mo coated soda-lime glass via a two-step process including DC sputtering of metallic precursor and following selenization.The Raman spectra indicate that as the Cu content increases from low to high,the CIGS film sequentially goes through three phase regimes:coexistence of ordered vacancy compound and chalcopyrite CIGS?CH-CIGS?phase,single CH-CIGS phase and coexistence of Cu_xSe and CH-CIGS phase.Moreover,the full width at half maximum of CIGS Raman peaks changes over Cu/?Ga+In?and reaches its minimum near Cu/?Ga+In?=0.9 due to better crystallinity and less disorder.Some empirical FWHM-Cu/?Ga+In?relationships were also observed.These results show that Raman spectroscopy could be used for preliminary estimation of the crystal phases and Cu content of CIGS film in a fast and non-destructive way.3.This dissertation studied the film forming mechanism of the chemical solution depositon?CSD?of CIGS,and determined a feasible process routine of CSD.The selenization process had been improved by developing a RTP salinization furnace with double temperature zone.The prototype solar cell was fabricated.These results provide a guide and technical approach for the development of low cost CIGS thin films and solar cells.4.Developed a magnetic transport measurement system,which is used to measure the electrical parameters of thin film materials.The magnetic transport measurement system consists of Hall measurement system and four-point probe instrument and realizes automatic measurement,analysis,data display and storage.The Hall coefficient,Current-Voltage curve and resistivity can be measured under various magnetic field and temperature by this system.