【作者】 杨波；

【导师】 唐江；

【作者基本信息】 华中科技大学 ， 光学工程， 2017， 博士

【摘要】 太阳能电池可以利用光电效应,有效的将光能转换为电能。由于具有优异的光电性能,薄膜太阳能电池受到了广泛关注。现阶段研究深入且已经商用的薄膜太阳能电池主要是碲化镉太阳能电池和铜铟镓硒太阳能能电池,然而铜铟镓硒中的In和Ga价格昂贵且稀缺,且碲化镉中的Cd有毒。因此,人们迫切希望能制备出一种廉价且环境友好的薄膜太阳能电池。通过研究发现锑基三元硫族化合物材料(CuSbS2和CuSbSe2)的禁带宽度合适、吸光系数高,且其中元素对环境友好,是一种优良的吸光层材料。本课题中我们主要研究CuSbS2和CuSbSe2薄膜在平面异质结太阳能电池中的应用,主要内容如下:(1)采用肼溶液法制备合成了Sb-S和Sb-Se肼溶液,通过Raman光谱系统研究了Sb在肼溶液中的溶解机理,并基于该前驱体溶液制备得到了组分可控、禁带宽度可调的Sb2(S1-xSex)3(0≤x≤1)合金薄膜,从而为锑基硫属化合物在太阳能电池中的应用打下坚实基础。(2)基于理论计算和实验系统研究了CuSbS2材料与光伏应用方面相关的基本性质,如缺陷物理、材料学、光学、电学性质。第一性原理(DFT)计算表明浅能级的点缺陷VCu由于其低的形成能成为最主要的受体缺陷,因此CuSbS2薄膜为本征p型半导体。同时,其余可能出现的受体缺陷(CuSb)和施主缺陷(Cui,SbCu和VS)的形成能和缺陷深度也得到了深入研究。采用肼溶液法且相对低温的退火温度(350 oC),我们成功得到了纯相且高质量的CuSbS2薄膜,并且系统研究了其材料学、光学以及电学方面的基本性质;基于该薄膜,我们制备了底衬结构的薄膜太阳能电池(玻璃基底/FTO/CuSbS2/CdS/ZnO/ITO/Au)并获得了0.50%的转换效率。(3)基于密度泛函理论,计算发现了在CuSbSe2材料无有害的深能级缺陷,并且其载流子浓度可以控制在一个适合光伏吸收层要求的范围内;通过肼溶液法制备得到了高质量的CuSbSe2薄膜,并且系统研究了其材料学、光学以及电学方面的基本性质;基于该薄膜制备了底衬结构的CdS/CuSbSe2异质结薄膜太阳能电池,器件效率为1.32%。(4)采用肼溶液法在不同的退火温度(100-520 oC)制备得到了一系列Cu-Sb-Se-S薄膜,且深入研究了薄膜物相组成、电学性质、晶体取向以及薄膜形貌与退火温度的依赖关系。特别地,在380°C或者400 oC退火得到的薄膜具有:i)单相的CuSb(Se0.96S0.04)2;ii)利于载流子传输的(013)和(112)晶面;iii)合适的载流子浓度(1017 cm-3量级)。以该薄膜为吸收层,我们制备了转换效率为2.70%的薄膜太阳能电池器件,表明了组分和取向控制在CuSbSe2光伏应用中的重要性。更多还原

【Abstract】 Solar cells,exploiting the photovoltaic effects,transform solar energy directly into electricity.Among them,thin-film solar cells have the advantages of low production cost,high power conversion efficiency and good device stability.What is more,they could be processed into flexible modules for a wide range of applications.Especially,solar cells based on CIGS and CdTe are intensively investigated.But,Due to the price issue of In and Ga and the toxity of Cd,we must seek novel solar cell materials with low-cost,non-toxity and high-efficiency materials.CuSbS2 and CuSbSe2 have sutiable bandgap and large absorption coefficients.Also,the elements of these two materials are all eco-friendly and inexpensive.This indicates that CuSbS2 and CuSbSe2 have the potential to be a successful absorber materials.In this thesis,the mateials properties and photovoltaic applicaitions of CuSbS2 and CuSbSe2 are thoroughly investigated.The following is the main content:(1)Using a hydrazine based solution process,single-phase Sb2(S,Se)3 films were successfully obtained.Through Raman spectroscopy,we have investigated the dissolution mechanism of Sb in hydrazine.Our study provides a valuable guidance for tuning the band gap in hydrazine solution processed Sb2(S,Se)3 alloy films for the future fabrication of improved photovoltaic devices.(2)Based on theoretical calculation and experimental investigation,the material properties(such as defect physics and photoelectric properties)related to photovoltaic application of CuSbS2 thin film were systematacially explored.Density functional theory calculations reveal that CuSbS2 has intrinsically p-type conductivity,which is determined by the dominant Cu vacancy(VCu)defects with a shallow ionization level and the lowest formation energy.Meanwhile,the formation energy and ionization level of other point defects were also studied.Using a hydrazine based solution process,phase-pure,highly crystalline CuSbS2 film with large grain size was successfully obtained.Also,the material and photoelectric properties were carefully investigated.Finally,we have built a prototype FTO/CuSbS2/CdS/ZnO/ZnO:Al/Au solar cell and achieved 0.50% solar conversion efficiency.(3)Using density functional theory calculations,CuSbSe2 is shown to have benign defect properties,i.e.,free of recombinationcenter defects,and flexible defect and carrier concentration.Next,systematic material,optical,and electrical characterizations uncover many unexplored fundamental properties of CuSbSe2.Finally,a prototype CuSbSe2-based thin film solar cell with an efficiency of 1.32% is fabricated by a hydrazine solution process,thus confirming the great potential of CuSbSe2 for thin-film solar cell applications.(4)Using a hydrazine based solution process,we have prepared a series of Cu-Sb-Se films by varying the annealing temperature from 100 to 520 °C.The dependence of phase composition,crystallographic orientation and electrical properties on annealing temperature were carefully studied.In particular,films prepared at 380 or 400 °C has the single-phase CuSb(Se0.96S0.04)2 with the tilted [013]-and [112]-oriented grains and low carrier concentration of ~1017 cm-3.Using this film as the absorber layer and CdS as the buffer,a photovoltaic device exhibiting 2.70% efficiency with a VOC of 0.27 V,JSC of 11.84 mA/cm2,FF of 40.51%(AM1.5G,100 mW/cm2)was obtained,showcasing the potential of CuSbSe2 for thin film solar cells.更多还原