多步旋涂过程中CsPbBr3无机钙钛矿成膜机理

在无机钙钛矿太阳能电池的研究中,薄膜制备工艺是影响钙钛矿太阳能电池光电转换效率(PCE)的重要因素之一. CsPbBr₃钙钛矿作为稳定性极好的无机钙钛矿之一,因其前驱体盐(PbBr₂, CsBr)溶解度差异过大,通常采用多步法进行制备.而由于对成膜机理的认识不充分,导致制备的薄膜存在薄膜形貌差、前驱体反应不完全等问题.本文通过旋涂不同次数的CsBr溶液,探究了CsPbBr₃钙钛矿的成膜机理.成膜过程中CsBr扩散进入预先沉积的PbBr₂薄膜完成反应,短暂反应时间使薄膜深层反应不充分而薄膜表面过度反应,CsPb₂Br₅和Cs₄PbBr₆等相伴随CsPbBr₃钙钛矿出现,反复退火形成的薄膜阻挡CsBr扩散加剧了这一现象.适当地延长前驱体的反应时间,能为CsBr扩散及反应提供更充分的空间.基于优化反应时间, CsPbBr₃钙钛矿薄膜形貌得到改善、其晶粒尺寸得到提升,钙钛矿薄膜...     

氯化钠/铯铅溴钙钛矿复合薄膜的原位制备及性能EI北大核心CSCD

全无机铯铅卤钙钛矿因其优异的光电性能受到广泛关注。然而,薄膜较差的稳定性和制备中大量昂贵且有毒有机溶剂的使用,严重阻碍了其商业化应用进程。在本工作中,水溶液被用作配制含氯化钠(NaCl)的钙钛矿前驱液的溶剂。通过一步溶液法获得原位生长的NaCl/CsPbBr_(3)钙钛矿复合薄膜,并在该过程中引入二甲基亚砜(DMSO)溶液来优化其晶体结构及光学性能。研究表明,NaCl和DMSO的协同作用可以调控复合薄膜中晶粒的形貌、提高相纯度并增强荧光发射。当DMSO和前驱体溶液体积比为1∶2时,复合薄膜呈现出最佳的绿光发射,荧光量子效率达48.2%。此外,得益于NaCl的有效复合及优化的晶体结构,所制备的复合薄膜具有增强的稳定性。该设计思路有利于制备柔性、大面积和高稳定性显示用荧光转换薄膜。     

激光辐照对热退火金属/掺氟二氧化锡透明导电薄膜光电性能的影响

采用532 nm纳秒脉冲激光对热退火的铝(Al)/掺氟二氧化锡(FTO)、铜(Cu)/FTO和银(Ag)/FTO三种双层复合薄膜表面分别进行处理, 结果显示薄膜样品的光电性能都得到提高.其中, 热退火Ag/FTO薄膜的平均透光率(400–800 nm)增幅最大, 从72.6%提高到80.5%, 主要是由于其表面产生了具有减反增透作用的光栅结构.激光辐照后热退火Ag/FTO薄膜的导电性也略有提高, 其方块电阻从5.6 Ω/sq下降到5.3 Ω/sq, 原因主要是激光辐照的热效应造成的退火作用使薄膜的晶粒尺寸增大, 减少了晶界散射而使载流子迁移率提高.计算结果显示, 激光辐照后热退火Ag/FTO薄膜的品质因子从0.73×10^-2Ω^-1增大为2.16×10^-2Ω^-1, 表明其综合光电性能得到显著提高.激光辐照可同步实现薄膜表面光栅结构的制备和附加退火作用, 这为金属层复合透明导电薄膜光电性能的综合优化提供了新的思路.     

钙钛矿薄膜气相制备的晶粒尺寸优化及高效光伏转换

钙钛矿薄膜的气相制备是一种极具潜力的工业化生产工艺,但薄膜的质量控制目前远落后于溶液制备法.本文通过建立PbI_2薄膜向钙钛矿薄膜完全转化过程中反应时间、晶粒尺寸与温度的关系,实现了薄膜的质量优化及大面积钙钛矿薄膜的制备,将薄膜的平均晶粒粒径从0.42μm优化到0.81μm.基于空间电荷限制电流模型对缺陷密度的研究显示,钙钛矿薄膜的缺陷密度由5.90×10~(16)cm~(–3)降低到2.66×10~(16)cm~(–3).光伏器件(FTO/TiO_2/C_(60)/MAPbI_3/spiro-OMeTAD/Au结构)测试显示,面积为0.045cm~2器件的平均光电转换效率从14.00%提升到17.42%,最佳光电转换效率达到17.80%,迟滞因子减小至4.04%.同时,基于180℃制备的1cm~2器件的光电转换效率达到13.17%.     

热退火对等离子体增强化学气相沉积SiCOH薄膜结构与性能的影响

热退火是多孔低介电常数薄膜制备过程中的重要一环, 对薄膜结构及性能具有重要影响. 本文以四乙氧基硅烷和双戊烯为前驱体, 采用等离子体增强化学气相沉积方法制备了SiCOH薄膜, 对其进行了氮气氛围下的热退火处理, 分析了热退火对薄膜结构与性能的影响, 探究了退火过程中薄膜结构变化的可能的反应机理. 傅里叶变换红外光谱和固体核磁共振谱结果表明, 沉积薄膜是一种有机无机杂化薄膜. 退火过程中, 薄膜中的-CH₂, -CH₃等有机组分被分解除去, 形成了以稳定的Si-O-Si等无机组分为骨架的多孔结构, 并通过氮气吸附/脱附等温线测试得到了验证. 在此期间, 薄膜骨架微结构亦发生一系列调整, C=C, Si-C含量增加, Si、O、C等元素间发生进一步键合. C=C 含量的提高, 使得薄膜的消光系数和漏电流密度增大. 实验证明, 退火后薄膜具有低折射率、低介电常数特性, 是一类具有优异的介电性能和力学性能的材料, 作为芯片后端互连层间介质具有极大的应用潜力.     

甲脒碘化铅单晶基钙钛矿太阳能电池的研究

近年来,CH(NH₂)₂PbI₃(FAPbI₃)由于其带隙接近理想值而受到了广泛关注,成为钙钛矿太阳能电池中最具吸引力的光电功能材料.然而由碘甲脒(FAI)和碘化铅(PbI₂)作为前驱体制备的传统钙钛矿层化学计量比不精准,缺陷密度大,稳定性差且结晶度较低,导致钙钛矿太阳能电池性能很难进一步提高.本文采用FAPbI₃单晶制备的钙钛矿薄膜具有高结晶度,高稳定性,精确的化学计量比和低缺陷密度.单晶钙钛矿薄膜的晶粒尺寸大,晶界少,导致晶界处缺陷较少,提高了钙钛矿太阳能电池的短路电流密度(J_SC)和开路电压(V_OC),使其光电转换效率有了大幅度的提高.本文为制备高稳定性、高结晶度和低缺陷密度的钙钛矿太阳能电池提供了一种有效策略.     

退火温度对电子束蒸发沉积Cu_2O薄膜性能的影响

近年来,钙钛矿太阳电池(PSCs)得到了迅猛发展,而无机空穴传输材料(IHTMs)的使用可进一步降低电池的成本,提高电池的稳定性.本文通过电子束蒸发制备了Cu_2O薄膜,研究了空气中退火温度及时间对薄膜组成、结构及光电性能的影响,并构筑了p-i-n反型平面异质结钙钛矿太阳电池.研究发现:由于热解作用,直接通过电子束蒸发制备的薄膜为Cu_2O和Cu的混合物;而在空气中经过退火后,由于氧化作用,随着退火温度的升高,薄膜的组分由混合物转变为纯的Cu_2O,再转变成纯的CuO.通过控制退火温度制备的Cu_2O薄膜的光学带隙约为2.5 eV,载流子迁移率约为30 cm~2·V~(-1)·s~(-1).应用于PSCs,薄膜的最佳厚度为40 nm,但电池性能低于PEDOT:PSS基的PSCs.这主要是由于钙钛矿前驱液在Cu_2O薄膜的润湿性较差,吸收层中有大量微孔洞存在,致使漏电流增强,电池的性能降低.然而,当采用Cu_2O/PEDOT:PSS双HTMs设计时,由于PEDOT:PSS对Cu_2O具有较强的腐蚀作用,使电池性能恶化.     

MOD法制备Bi4-xLaxTi3O12铁电薄膜及其谱图分析

采用有机金属沉积法(MOD)制备了Bi4Ti3O12(BIT)和Bi3.25La0.75Ti3O12(BLT)前驱体溶液,分别在单晶硅基片上制备了BIT和BLT铁电薄膜.前驱体溶液的干凝胶粉体和铁电薄膜分别用红外光谱(FTIR)、拉曼光谱和环境扫描电镜(ESEM)进行了表征.结果表明600℃时晶粒实现了由焦绿石相向类钙钛矿相结构的完全转变;温度升高,晶粒尺寸增大,薄膜结晶效果得到改善;引入镧使Ti-O和Bi-O键吸收峰位置向低波数频移,高温时频移率较大;500℃热处理时,干凝胶中乙二醇甲醚、乙酰丙酮完全分解,温度超过600℃后,残留的水及硝酸根离子挥发或分解.     

碘化钾对两步法制备钙钛矿薄膜及其电池性能的影响

有机-无机杂化钙钛矿太阳电池因具有光电转化效率高和制备成本低廉等优点而备受关注.钙钛矿薄膜中的缺陷是限制钙钛矿电池性能进一步提升的重要因素,而缺陷调控又依赖于薄膜制备方法的发展和进步.两步法是制备钙钛矿薄膜和电池的主要方法之一,但目前对在两步法前驱液中引入添加剂如何影响钙钛矿薄膜结晶过程和缺陷密度的认识不足.本工作致力...     

热处理对TbDyFe薄膜性能的影响

采用磁控溅射方法利用镶嵌靶材制备非晶TbDyFe薄膜,然后分别在150,300,450,550℃下退火,研究了热处理对TbDyFe薄膜性能的影响.结果显示,550℃温度下退火的样品出现RFe2相.随着退火温度的升高,晶粒逐渐长大,空洞网络变短而宽.薄膜的磁特性显示,其矫顽力及矩磁比均在出现RFe2相的550℃退火的样品中达到最大值.随着退火温度的增加,薄膜的易磁化轴从垂直膜面方向向平行膜面方向转动.     

Understanding the synergistic effect of mixed solvent annealing on perovskite film formation

Morphology control of perovskite films is of critical importance for high-performance photovoltaic devices. Although solvent vapor annealing (SVA) treatment has been widely used to improve the film quality efficiently, the detailed mechanism of film growth is still under construction, and there is still no consensus on the selection of solvents and volume for further optimization. Here, a series of solvents (DMF, DMSO, mixed DMF/DMSO) were opted for exploring their impact on fundamental structural and physical properties of perovskite films and the performance of corresponding devices. Mixed solvent SVA treatment resulted in unique benefits that integrated the advantages of each solvent, generating a champion device efficiency of 19.76% with improved humidity and thermal stability. The crystallization mechanism was constructed by conducting grazing-incidence wide-angle x-ray diffraction (GIWAXS) characterizations, showing that dissolution and recrystallization dominated the film formation. A proper choice of solvent and its volume balancing the two processes thus afforded the desired perovskite film. This study reveals the underlying process of film formation, paving the way to producing energy-harvesting materials in a controlled manner towards energy-efficient and stable perovskite-based devices.     

溶剂对钙钛矿薄膜形貌和结晶性的影响研究

溶剂对钙钛矿太阳能电池器件有着至关重要的影响. 基于目前常用的N, N-二甲基甲酰胺(DMF)和丁内酯(GBL)溶剂, 一步溶液旋涂技术和介孔电池结构, 制备的钙钛矿薄膜的形貌、结晶性, 以及最终的器件光电转化效率存在较大的差异, 利用DMF作为溶剂, 效率仅为2.8%, 而基于GBL的电池效率可以达到10.1%. 结合SEM, HRTEM, XRD和UV等表征手段, 分析了钙钛矿从DMF溶液和GBL溶液中结晶析出的不同机理, 明确了溶剂跟PbI₂的配位作用对钙钛矿的溶解、析出过程的制约作用, 揭示了造成器件效率差异的本质原因.     

Comparison of implantation and diffusion behavior of Ti, Sb and N in ion-implanted single crystal and polycrystalline ZnO: A SIMS study

Implantation and diffusion behavior of Sb, Ti and N in ZnO single crystal and sputter deposited thin films were studied through secondary ion mass spectrometric studies on ion-implanted and thermally annealed samples. Sb was implanted and Ti and N were co-implanted into ZnO single crystals and polycrystalline thin films on Si substrates at room temperature. The implanted samples were then annealed at 800 °C. Depth profiles of implant distributions before and after annealing were examined by Secondary Ion Mass Spectrometry (SIMS). As expected, implant range is sensitive to the mass of the dopants; and the dopant distribution is broadened as implanted elements migrate deeper into the film on thermal annealing. While diffusion of N in the ZnO thin film is not significant, Ti tends to diffuse deeper into the sample during annealing. For Ti and N co-implanted single crystal, annealing induced diffusion causes more redistribution of the lighter N than Ti. In general, implanted dopants diffuse more easily in thin films compared to the single crystal due to the presence of grain boundaries in the latter.     

KTN thin films prepared by pulsed laser deposition on transparent single crystal quartz(100)

Using the Sol-Gel method to produce the KTN ultrafine powder and the sintering technique with K2O atmosphere to prepare KTN ceramics as the targets instead of the KTN single crystal, highly oriented KTN thin films were produced on the transparent single crystal quartz (100) by the pulsed laser deposition (PLD). Since the thermal stress sustained by the quartz is relatively small, the limit temperature of the quartz substrates (300℃) is much lower than that of the P-Si substrates (560℃); the prepared thin film is at amorphous state. Increasing the pulsed laser energy density in the process incorporated with annealing the film after deposition at different temperatures converts the amorphous films into crystal. The optimal pulsed laser energy density and annealing temperature were 2.0 J/cm2 and 600℃, respectively. A discussion was made to understand the mechanism of film production at relatively low substrate temperature by PLD and effects of the annealing temperatures on the forming of the perovskite p     

基于溶剂化效应的BDE-15分子振动光谱增强特征振动研究

利用密度泛函与自洽反应场理论在B3LYP/6-31+G(d)水平下分别计算气态及24种不同极性溶剂中4,4’-二溴二苯醚(4,4’-dibrominated diphenyl ethers, BDE-15)的分子振动光谱(红外光谱、拉曼光谱),以气态分子振动光谱为基准,筛选出对溶剂极性敏感的特征振动作为指标构建溶剂对BDE-15振动光谱溶剂化效应指标体系,探究溶剂对BDE-15分子振动频率、红外/拉曼峰强溶剂化效应及综合效应,并寻求显著增强BDE-15分子特征振动频移/强度的溶剂。研究表明：从分子振动频率角度,溶剂极性敏感的(频移>1 cm-1)分子特征振动均为伸缩振和面外弯曲振,但24种溶剂对BDE-15分子振动频率溶剂化效应并不显著;从分子振动峰强角度,24种溶剂对BDE-15分子振动光谱峰强的增强效应主要发生在红外光谱的中低频区及拉曼光谱的高频区,其中起显著增强(红外/拉曼效应指标值分别大于6与5)的溶剂为醇类、乙腈、二甲亚砜、硝基苯;不同极性溶剂对BDE-15拉曼峰强溶剂化效应及综合效应指标值均表现出随溶剂介电常数增长由线性到对数的增长趋势,而红外峰强只保留低介电常数溶剂时的线性关系。利用上述BDE-15分子振动光谱峰强增强方法对BDE-153,BDE-154和BDE-209进行验证,醇类、乙腈、二甲亚砜、硝基苯对三者的振动光谱红外/拉曼峰强的效应指标值分别大于6与5,且最大峰强增倍数皆大于33,说明所建BDE-15分子振动光谱增强特征振动方法有助于进一步开展基于分子振动光谱的PBDEs同系物间辨识研究。     

Local phase decomposition as a cause of polarization fatigue in ferroelectric thin films

We show that lead zirconate titanate thin films undergo local phase decomposition during fatigue. The original remanent polarization of the fatigued film is completely restored after furnace annealing in an O2 atmosphere, following a significant regrowth of a perovskite phase from the pyrochlorelike structure. By comparing our data with other researchers' work on annealing of fatigued ferroelectric samples, we conclude that local phase separation is the generic reason for electrical fatigue in ferroelectrics. A fatigue model is proposed in order to interpret our experimental data.     

Influence of oxygen on diffusion in the Cu/Mo/Au system

The annealing behaviour of the Cu/Mo/Au metallization system is investigated. Backscattering spectrometry reveals a rapid diffusion of Cu and Au across the Mo film and the formation of AuCu after annealing at 600°C for 30 min in vacuum, but only when no impurity is detected in the as-deposited polycrystalline Mo layer. The Au-Cu interaction is impeded when 5.5 at% of oxygen is introduced in the as-deposited Mo layer. The thin film microstructures are analyzed using X-ray diffraction and transmission electron microscopy. The thermal stability difference between the samples with a pure Mo layer and a contaminated Mo layer is discussed in terms of fast diffusion process inhibited by a grain boundary decoration with oxygen atoms.     

退火处理对磁控溅射制备LaCoO_3薄膜性能的影响

采用磁控溅射法在硅衬底上制备了LaCoO_3(LCO)薄膜,研究了退火温度对LCO薄膜组织结构、表面形貌及热电特性的影响,并利用X射线衍射仪、原子力显微镜(AFM)、激光导热仪等对LCO薄膜的晶体结构、表面形貌、热扩散系数等进行测量与表征.结果表明:退火温度对LCO薄膜的结晶度、晶粒尺寸和薄膜表面形貌都有较大影响;退火前后LCO薄膜的热扩散系数都随温度的升高而减小,且变化速率逐渐减缓; LCO薄膜的热扩散系数随退化温度的升高先增大后减小.LCO薄膜经过700℃退火后得到最佳的综合性能,其薄膜表面致密、平整,结晶质量最好,热扩散系数最小,热电性能最好.     

真空闪蒸法制备钙钛矿薄膜的光学性质研究

近年来,以有机无机杂化铅卤钙钛矿为吸光层的薄膜太阳能电池受到了广泛的关注,不到十年时间其光电转换效率已经从3.8%提高到了23%,这主要归因于有机铅卤钙钛矿材料光吸收系数高,带隙合适并易于调控,电子-空穴扩散长度长等优点。2016年Gr?tzelL等人利用低气压快速去除薄膜前驱体溶剂的方法,获得了高质量的甲脒和溴离子掺杂钙钛矿薄膜。相比于其他传统的溶液制备方法,这种方法能够很好的解决大面积均匀性的问题,为高效率、大面积钙钛矿太阳电池产业化提供了可能。钙钛矿薄膜的成份、结构及其光学性能对于太阳电池的器件性能起决定性作用,因此在该制备技术下,研究不同掺杂种类钙钛矿薄膜对光学性质的影响具有积极的意义。利用真空闪蒸溶液技术制备了3种成分的钙钛矿薄膜,利用扫描电镜、 X射线衍射,吸收光谱和荧光光谱等表征手段对薄膜的形貌、结构和光学性质进行了研究。结果表明,该技术可以用于制备均匀致密、无针孔的高质量甲脒、溴离子掺杂和氯离子掺杂的钙钛矿薄膜(成分分别为(FAPbI3)0.85(MAPbBr3)0.15,MA3PbI3和MAPb(IxCl1-x)3),薄膜中晶粒的尺寸分别为500, 100和200 nm左右;薄膜的形成过程为溶剂中的DMSO与钙钛矿配位,并在真空闪蒸过程中快速形成相对稳定中间相,经过加热后,薄膜中的DMSO被去除并形成钙钛矿晶体,结构为四方相;甲脒、溴离子和氯离子掺杂的薄膜对可见光有强烈的吸收作用,薄膜吸收边均在750 nm左右;薄膜的掺杂对带隙宽度没有明显影响, 3种成份的薄膜带隙宽度位于1.6 eV左右;甲基胺碘化铅的荧光发射峰在765 nm,甲脒和溴离子掺杂后发光峰位红移至774 nm,氯离子掺杂后薄膜峰位处于761 nm,有微弱的蓝移,且强度出现下降。这可能是晶粒尺寸和薄膜内部缺陷变化导致的。     

Microstructure and electrical properties of Ba0.5Sr0.5TiO3 thin films prepared on copper foils with La2O3 buffer layers

Ba_0.5Sr_0.5TiO₃ (BST) thin films were deposited on copper foils via sol-gel method with La₂O₃ as a buffer layer. The films were processed in almost inert atmosphere so that the substrate oxidation was avoided while allowing the perovskite film phase to crystallize. The existence of a La₂O₃ buffer layer between the BST thin film and Cu foil improved the dielectric constant and reduced the leakage current density of the BST thin film. Meanwhile, the BST thin film exhibited ferroelectric character at room temperature, which was contrast to the para-electric behavior of the film without the buffer layer. Effects of La₂O₃ buffer layer on the crystallizability and microstructure of BST thin films were also investigated.