The Fabrication Of Cu₂ZnSn?S,Se?₄ Absorber Layer And The Optimization Of The Thin Film Solar Cell

Chalcogenide semicondouctor photovoltaic device,copper zinc thin sulfide-based thin film solar cells have developed on the basis of copper indium gallium seleniumbased thin film solar cells.The chemical elements of absorber layer are environmentally friendly and earth-abundant,and the absorber material is direct bandgap semiconductor with adjustable bandgap energies in the range of 1.0e V¹.5e V,otherwise the abseorber material has high absorption coefficient in the visible light range.Due to these advantages Cu₂ZnSn?S,Se?₄ semicondouctor photovoltaic device has became a promising alternative for thin films solar cells.This work is focused on the fabrication of Cu₂ZnSn?S,Se?₄ thin film absorbers after annealed and the improvement of different function layers of Cu₂ZnSnS₄ thin film solar cell.The precursors were prepared by Ion Beam Sputtering Deposition?IBSD?.Then we explored the optimal strategies of sulfurization and selenization,and the preparation parameters of different function layers.At last the Cu₂ZnSn?S,Se?₄ thin film solar cell and the Cu₂ZnSnS₄ have been achieved successfully.Detailed research contents of my work are shown as follw:Firstly,the preparation process of Cu₂ZnSn?S,Se?₄ thin film absorbers after annealed were studied.Including the fabrication of annealed at the atmosphere of Ar,the fabrication of sulfurization,and the fabrication of selenization.Under different conditions of annealing,the effects of temperature and duration were studied.At first.the Cu₂ZnSn?S,Se?₄ precursors were annealed at the atmosphere of Ar.For the annealed samples,Cu₂ZnSn?S,Se?₄ thin film annealed at 450? for 1h shows a good crystallographic quality,the biggest crystal size,the lesser second phase,and a 1.21 e V band gap.Due to the unfavorable reactions,the sample has lots of defects,so it can not be used as the absorber layer.In order to decrease the unfavorable reactions,the sulfurization was used to fabricate Cu₂ZnSn?S,Se?₄ absorber layer.It was revealed that the film sulfurized at 600? for 30 min shows the best crystallographic quality,the biggest crystal size,the lesser second phase,and a 1.44 e V band gap.Alaso,the selenization was used to fabricate Cu₂ZnSn?S,Se?₄ absorber layer.The refined growth condition is at 580? and duration for 30 min.Under these conditions,the thin films show a good crystallographic quality,a compact and uniform surface,and a 0.91 e V band gap.Secondly,the Cu₂ZnSnS₄ thin film solar cell was modified by improving the Mo back contect,optimizing the Cd S buffer layer,choosing and optimizing the transparent conductive oxide?TCO?.The sulfuration of Mo back contact can not only restrain the unfavorable reaction between absorber layer and back contact,but also improve the open circuit voltage,the fill factor,and the conversion efficiency.The Cd S thin film was fabricated as the buffer layer of the solar cell.The AZO and ITO materials were used to made the TCO layer of the solar cell.The conversion efficiency of solar cell fabricated by ITO material were higher than the solar cell made by AZO material.Otherwise,low temperature annealing can improve the photoelectric properties of the solar cell made by ITO material.Thirdly,the IBSD was used to fabricate Cu₂ZnSn?S,Se?₄ precursors and solar cells,the conversion efficiency of Cu₂ZnSn?S,Se?₄ is 1.1%.Also,Cu₂ZnSnS₄ solar cell was fabricated,and the conversion efficiency reached 4.6%.