Zn_(1–x)Mg_xO能带结构及作为窗口层的CdTe薄膜太阳电池的SCAPS仿真应用
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摘要
采用第一性原理广义梯度近似+U(GGA+U)方法计算了纤锌矿结构Zn_(1–x)Mg_xO(ZMO)(0≤x≤0.25)合金的能带结构。计算表明:随着Mg组分增加,ZMO化合物的导带底及费米能级均向真空能级方向移动,带隙增宽。基于理论计算得到ZMO的能带结构参数,使用SCAPS软件对ZMO作窗口层的CdTe薄膜太阳电池的性能进行了仿真模拟,并将研究结果与CdS作窗口层的CdTe太阳电池的性能进行了比较。结果表明:Mg在ZMO中的含量0≤x≤0.125时,ZMO/CdTe太阳电池具有比CdS/CdTe太阳电池更高的开路电压和短路电流密度;ZMO的导带底高出CdTe导带底约0.13 e V时,CdTe薄膜太阳电池的转换效率最高,达到18.29%。这些结果为高效率碲化镉薄膜太阳电池的结构设计和器件制备提供了理论指导。
In this paper, the band structure of Zn_(1–x)Mg_xO(ZMO) alloy with different Mg compositions by using first-principles calculations with GGA+U method was studied. The calculation results show that position of conduction band offset and Fermi level of Zn_(1–x)Mg_xO move towards the vacuum level while the band gap becomes wider with the increasing Mg concentration. Based on theoretical calculation results of ZMO, ZMO/CdTe, CdS/CdTe solar cells were modeled using SCAPS software and its device performances were simulated and analyzed in detail. The results indicate that the conversion efficiency of CdTe solar cell with ZMO is higher than that of solar cell with CdS due to the high open circuit voltage and short circuit current density when x in Zn_(1–x)Mg_xO is in the range of 0-0.125. Efficiency of CdTe solar cells with ZMO reaches 18.29% because the recombination decreases obviously resulting from appropriate conduction band offset about 0.13 e V at ZMO/CdTe interface. These data provide a theoretical guidance for design and fabrication of high efficiency CdTe solar cells.
In this paper, the band structure of Zn_(1–x)Mg_xO(ZMO) alloy with different Mg compositions by using first-principles calculations with GGA+U method was studied. The calculation results show that position of conduction band offset and Fermi level of Zn_(1–x)Mg_xO move towards the vacuum level while the band gap becomes wider with the increasing Mg concentration. Based on theoretical calculation results of ZMO, ZMO/CdTe, CdS/CdTe solar cells were modeled using SCAPS software and its device performances were simulated and analyzed in detail. The results indicate that the conversion efficiency of CdTe solar cell with ZMO is higher than that of solar cell with CdS due to the high open circuit voltage and short circuit current density when x in Zn_(1–x)Mg_xO is in the range of 0-0.125. Efficiency of CdTe solar cells with ZMO reaches 18.29% because the recombination decreases obviously resulting from appropriate conduction band offset about 0.13 e V at ZMO/CdTe interface. These data provide a theoretical guidance for design and fabrication of high efficiency CdTe solar cells.
引文
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[2]OZGUR U,ALIVOV YA I,LIU C,et al.A comprehensive review of Zn O materials and devices.Appl.Phys.Lett.,2005,98(4):1–11.
[3]OHTOMO A,KAWASAKI M,KOIDA T,et al.MgxZn1–xO as a II–VI widegap semiconductor alloy.Appl.Phys.Lett.,1998,72(19):2466–2468.
[4]KUMAR P,MALIK H K,GHOSH A,et al.Bandgap tuning inhighly c-axis oriented Zn1-xMgxO thin films.Appl.Phys.Lett.,2013,102(22):1–5.
[5]HUANG D,SHANG Y Z,CHEN D H.First-principles calculation on the electronic structure and absorption spectrum of the wurtzite Zn1–xMgxO alloys.Acta.Phys.Sin.,2008,57(02):1078–1083.
[6]ZHANG X D,GUO M L,LIU C L,et al.First-principles investigation of electronic and optical properties in wurtzite Zn1-xMgxO.Eur.Phys.B,2008,62(4):417–421.
[7]BAI L N,LING J S,JIANG Q.Optical and electronic properties of wurtzite structure Zn1-xMgxO alloys.Chin.Phys.Lett.,2011,28(11):1–4.
[8]THANGAVEL R,PRATHIBA G,NAANCI B A,et al.First principle calculations of the ground state properties and structural phase transformation for ternary chalcogenide semiconductor under high pressure.Computational Materials Science,2007,40(2):193–200.
[9]FAN X F,SUN H D,SHEN Z X.A first-principle analysis on the phase stabilities,chemical bonds and band gaps of wurtzite structure AxZn1-xO alloys(A=Ca,Cd,Mg).Condens.Matter.Phys.,2008,20(23):221–235.
[10]WENG Z Z,ZHANG J M,HUANG Z G,et al.Effect of oxygen vacancy defect on the magnetic properties of Co-doped Zn O.Chin.Phys.Lett.,2011,20(2):422–427.
[11]CHO J Y,KIM I K,JUNG I O,et al.Effects of Mg doping concentration on the band gap of Zn O/MgxZn1-xO multilayer thin films prepared using pulsed laser deposition method.Journal of Electroceramics,2009,23(2/3/4):442–446.
[12]TAKASHI MINEMOTO,YASUHIRO HASHIMOTO,TAKUYA SATOH,et al.Cu(In,Ga)Se2 solar cells with controlled conduction band offset of window/Cu(In,Ga)Se2 layers.Journal of Applied Physics,2001,89(12):8327–8330.
[13]张静全.硫化镉及相关化合物多晶薄膜与碲化镉太阳电池研究.成都:四川大学博士学位论文,2002.
[14]SEGALL M D,LINDAN P J D,PROBERT M J,et al.First-principles simulation:ideas,illustrations and the CASTEP code.Phys.Condens.Matter.,2002,14:2717–2744.
[15]ZHAO Y,TRUHLAR D G.Construction of a generalized gradient approximation by restoring the density gradient expansion and enforcing a tight Lieb–Oxford bound.The Journal of Chemical Physics,2008,128(18):1–8.
[16]FISCHER T H,ALMLOF J.General methods for geometry and wave function optimization.Journal of Physical Chemistry.Chem.,1992,96(24):9768–9774.
[17]HE X,HE L,TANG M J,et al.Effects of the vacancy point-defect on electronic structure and optical properties of Li F under high pressure:a first-principles investigation.Acta Phys.Sin.,2010,60(2):2–10.
[18]ODAKA H,IWATA S,TAGA N,et al.Study on electronic structure and optoelectronic properties of indium oxide by first-principles calculations.Japanese Journal of Applied Physics,1997,36(36):5551–5554.
[19]SHEETZ R M,PONOMAREVA I,RICHTER E,et al.Defect-induced optical absorption in the visible range in Zn O nanowires.Physical Review B Condensed Matter.,2009,80(19):195314-1-4.
[20]SHUKLA G,KHARE A.Effect of Mg doping and substrate temperature on the properties of pulsed laser deposited epitaxial Zn1-xMgxO thin films.Appl.Phys.A,2009,96(3):713–719.
[21]USUDA M,HAMADA N,KOTANI T,et al.All-electron GW calculation based on the LAPW method:application to wurtzite Zn O.Phys.Rev.B,2002,66(12):1–10.
[22]BURGELMAN M,NOLLET P,DEGRAVE S.Modelling poly crystal line semiconductor solar cells.Thin Solid Films,2000,362(99):527–532.
[23]HENINI M.Semiconductors:Data Handbook:Otfried Madelung(ed.);Springer,ISBN3-540-40488-0.Microelectronics Journal,2004,35(8):685.
[24]GUO J,WANG W,LIU G,et al.Investigation of Cd Te/Cd S heterojunction characteristics.Acta Energiae Solaris Sinica,2003,24(2):269–272.
[25]CHEN Y L,WANG F G,WU L L.Properties of indium doped Cd S thin films and their photovoltaic application in Cd Te solar cells.Chalcogenide Letters,2017,14(1):1–9.
[26]HUANG C H,CHUANG W J.Dependence of performance parameters of Cd Te solar cells on semiconductor properties studied by using SCAPS-1D.Vacuum,2015,118:32–37.