碳电极钙钛矿太阳能电池光吸收层厚度对光伏性能的影响研究

本文使用两步法,通过控制PbI₂(DMSO)溶液的浓度制备了不同厚度的有机-无机杂化钙钛矿(MAPbI₃)光吸收层薄膜,并组装了大面积基于碳电极且无空穴传输层的钙钛矿太阳能电池。对不同厚度MAPbI₃光吸收层薄膜的晶相、光吸收性质、表面形貌、元素组成进行分析,并进一步测试了基于MAPbI₃薄膜制备的钙钛矿太阳能电池的光伏性能。结果表明,MAPbI₃光吸收层薄膜厚度与PbI₂(DMSO)浓度呈正相关关系,浓度为1.3 mol/L的PbI₂溶液制备的MAPbI₃薄膜厚度约为350 nm,具有较好的结晶度和光吸收强度,且薄膜表面致密平整,无明显缺陷,基于350 nm MAPbI₃光吸收层的钙钛矿太阳能电池获得了8.48%的光电转换效率。     

Boron-doped a-SiOx:H films prepared by photo-CVD technique

The optoelectronic and structural properties of p-type a-SiO_x:H films have been studied. The deposition parameters e.g. chamber pressure and diborane to silane ratio are optimized to get a film with dark conductivity (σ_d) 7.9×10⁻⁶ S cm⁻¹ and photoconductivity 9.3×10⁻⁶ S cm⁻¹ for an optical gap (E₀₄) of 1.94 eV. The decrease of optical gap accompanied by the increase of conductivity is due to less oxygen incorporation in the film, which is substantiated by the decrease of the intensity of SiO absorption spectra. The properties are very much effected by the chamber pressure and diborane to silane ratio.     

Bi26-x-yMxNyO40(M,N=Fe,Co,Gd)软铋矿薄膜的制备和强磁光效应

磁光材料是现代光通信产业中不可或缺的关键功能材料。为了实现光通信器件的小型化,高质量磁光薄膜材料受到关注。软铋矿型Bi₂₅FeO₄₀具有高对称性的立方晶体结构,单位体积所含铋离子浓度高,理论上应具有较强的磁光效应,但却因为磁性偏弱、制备困难等缺点而限制了其应用。本文采用射频磁控溅射法,在掺钇二氧化锆(YSZ)基底上沉积获得具有立方相软铋矿型结构的Bi_26-x-yM_xN_yO₄₀ (M, N=Fe, Co, Gd)磁光薄膜,并对其形貌、磁性、透过率、磁圆二色信号等进行表征。结果表明,薄膜均较为平整,厚度约为190 nm,在近红外区的透过率约为60%~70%。薄膜的磁性随着掺杂离子含量的提高逐渐增强。Bi_13.6Gd_2.7Co_4.0Fe_5.7O₄₀/YSZ薄膜具有强磁光效应,在716 nm处的磁圆二色光谱信号高达到1 710 deg/cm,有望应用于集成光隔离器等光通信器件中。     

Gd3+、Co3+共掺杂铁酸铋薄膜多铁性增强及带隙调谐

多铁功能材料在现代生产生活中有举足轻重的作用。本文采用溶胶-凝胶法以硝酸铁、硝酸铋、硝酸钆、硝酸钴为原料,乙二醇甲醚为溶剂,柠檬酸作螯合剂制成前驱体溶液,通过旋涂法在Pt/Ti/SiO₂/Si及ITO衬底上合成Bi_0.85Gd_0.15Fe_1-xCo_xO₃ (x=0, 0.04, 0.08, 0.12)薄膜,研究了Gd³⁺、Co³⁺共掺杂对薄膜铁电性能、磁学性能及光学带隙的影响。XRD结果表明所有薄膜均呈(111)方向的菱形结构,SEM结果表明共掺杂可以细化晶粒。根据铁电性和漏电流测试分析结果可知在Co³⁺掺杂量为8%时最大剩余极化值达到2P_r=15.71 μC/cm²,所有样品的漏电流传导机制均为欧姆传导机制。根据磁学性能测试分析结果可知,共掺杂可以有效增强薄膜的饱和磁化强度,且在Co³⁺掺杂量为8%时最大饱和磁化强度达到37.78 emu/cm³。根据吸收光谱及Tauc公式拟合结果可知共掺杂可以有效减小薄膜的光学带隙且随着掺杂量的增加光学带隙逐渐减小,在Co³⁺掺杂量为12%时光学带隙减小到1.96 eV。     

Surface modification of SiO2 glass by laser processing

Various oxide films on SiO₂ glass substrates were irradiated by a laser beam. A continuous CO₂ laser source (wavelength 10.6 μm) was used for this purpose; the composition change at the surface layer was determined by Rutherford backscattering spectrometry (RBS). All the alkaline-earth oxides as well as those of lanthanum and yttrium, entered the glass after treatment. ZrO₂ and CeO₂, however, did not enter the SiO₂ glass due to laser irradiation. It is interesting, however, that a film of ZrO₂ + Al₂O mixture easily entered into the SiO₂ glass by laser processing. The conditions and mechanism of laser-enhanced interaction of ZrO₂ or other oxide films with SiO₂ glass surfaces are discussed especially in view of their structural behaviour in glass.     

射频磁控溅射氧气流量对制备的Ga2O3∶Cr薄膜光致发光性能的影响

在不同氧气流量下,采用双靶射频磁控共溅射的方法在蓝宝石(α-Al₂O₃)基底上制备得到系列掺Cr的Ga₂O₃(Ga₂O₃∶Cr)薄膜,详细研究了薄膜在900 ℃退火前后的结构和光学性能。结果表明,未退火的Ga₂O₃∶Cr薄膜为非晶结构,其发光主要位于蓝绿波段。经900 ℃退火后,薄膜的结构由非晶变为多晶,且在近红外波段观测到了来源于Cr³⁺掺杂的发光。退火后的薄膜结晶质量和近红外发光均与氧气流量密切相关,而其光学带隙不受氧气流量的影响。在所研究的氧气流量范围,4 mL/min氧气流量下薄膜的近红外发光强度最强,这与此条件下薄膜结晶质量较好以及Cr³⁺替代Ga³⁺的数量较多有关。以上研究成果可为制备高质量Ga₂O₃∶Cr薄膜提供参考。     

Epitaxial growth of the CoFe2O4 film on SrTiO3 and its characterization

Cobalt ferrite (CoFe₂O₄) thin film is epitaxially grown on (0 0 1) SrTiO₃ (STO) by laser molecular beam epitaxy (LMBE). The growth modes of CoFe₂O₄ (CFO) film are found to be sensitive to laser repetition, the transitions from layer-by-layer mode to Stranski–Krastanov (SK) mode and then to island mode occur at the laser repetition of 3 and 5 Hz at 700 °C, respectively. The X-ray diffraction (XRD) results show that the CFO film on (0 0 1) SrTiO₃ is compressively strained by the underlying substrate and exhibits high crystallinity with a full-width at half-maximum of 0.86°. Microstructural studies indicate that the as-deposited CFO film is c-oriented island structure with rough surface morphology and the magnetic measurements reveal that the compressive strained CoFe₂O₄ film exhibits an enhanced out-of-plane magnetization (190 emu/cm³) with a large coercivity (3.8 kOe).     

In-situ RHEED study on the effect of light irradiation on Ge/Si heteroepitaxial growth by GeH4 source MBE

Effects of light irradiation on growth processes in the initial stage of growth of Ge films on (100)Si substrates by gas source molecular beam epitaxy using GeH₄ have been investigated by in-situ RHEED observations. It has been found that the growth rate is enhanced by an Ar⁺ ion laser and a D₂ lamp irradiation, and, moreover, that the growth process sequence of the Ge films irradiated by the Ar⁺ laser and D₂ lamp is the same as that without irradiation. The irradiation effect on the photolysis of GeH₄ gas has been examined by mass spectroscopy. The increase of the growth rate is due to the photolysis of GeH₄ and the excitation of substrate surfaces by vacuum-ultraviolet light in the D₂ lamp irradiation, and is due to only the excitation of substrate surfaces in the Ar⁺ laser irradiation.     

Oscillator strength of the infrared absorption band near 1080 cm in SiO2 films

It has been well known that the absorption maximum of the peak near 1080 cm⁻¹ in amorphous SiO₂ films shifts continuously with variation of thickness and properties such as stress. This is a first report on the oscillator strength of the absorption against frequency at the absorption maximum. SiO₂ films on silicon wafers were prepared by thermal growth in either dry O₂ or an O₂/H₂ mixture or liquid-phase deposition in HF saturated with silica gel. The oscillator strength continuously decreased from 1×10⁻⁴ down to 1×10⁻⁵ with the frequency shift from 1099 to 1063 cm⁻¹.     

Microstructure and ferroelectric properties of BaTiO3 films on LaNiO3 buffer layers by rf sputtering

We have fabricated LaNiO₃ and BaTiO₃ films using the rf sputtering method. The LaNiO₃ were deposited on Si substrates, demonstrating a (1 0 0) highly oriented structure and nanocrystalline characteristic with a grain size of 30 nm. The BaTiO₃ thin films were deposited on the LaNiO₃ buffer layers, and have exhibited a (1 0 0) texture with a thickness of 400 nm. A smooth interface is obtained between the LaNiO₃ bottom electrode and the BaTiO₃ film from cross-section observations by scanning electron microscopy. The bi-layer films show a dense and column microstructure with a grain size of 60 nm. Ferroelectric characterizations have been obtained for the BaTiO₃ films. The remnant polarization and coercive field are 2.1 μC/cm² and 45 kV/cm, respectively. The leak current measurements have shown a good insulating property.     

ZrO2对Ho∶(Y0.7Sc0.3)2O3激光陶瓷致密化和光学性能的影响

2 μm 波段处于人眼安全波长,在医疗、加工、红外探测与对抗,以及大气环境监测等军、民两用领域有着重要潜在和实际应用。Ho³⁺掺杂倍半氧化物陶瓷具有宽的吸收和发射光谱、高热导率以及低声子能量等优点,是一类重要的 2 μm 波段激光材料。通过材料固溶原理,可以实现光谱更加宽化,这使其有可能成为一类性能优异的中红外固体激光材料。本文以商业Y₂O₃、Sc₂O₃以及Ho₂O₃粉体为原料,添加少量ZrO₂(原子比为0~1.0%)作为烧结助剂,采用真空预烧,结合热等静压烧结的工艺,成功制备出高透明的0.5%Ho∶(Y_0.7Sc_0.3)₂O₃陶瓷。研究了ZrO₂掺杂浓度(0~1.0％)对Ho∶(Y_0.7Sc_0.3)₂O₃激光陶瓷致密化过程和光学性能的影响。通过添加ZrO₂有效抑制了高温下Ho∶(Y_0.7Sc_0.3)₂O₃陶瓷晶粒的生长,掺杂1.0％ZrO₂的Ho∶(Y_0.7Sc_0.3)₂O₃陶瓷经1 690 ℃下真空预烧结4 h和1 600 ℃/190 MPa热等静压烧结3 h后,其透过率在1 100 nm处达到79.1％(厚度为4.4 mm),接近理论透过率。     

Optical properties of hydrogenated amorphous silicon films doped with fluorinated gases

Doped amorphous silicon films were prepared by plasma-enhanced chemical vapour deposition of silane and hydrogen mixtures, using phosphorus pentafluoride (PF₅) and boron trifluoride (BF₃) as dopant precursors. The films were studied by UV-vis spectroscopy and their photo and dark conductivity were measured, the latter as a function of temperature. The optical gap of the n-type samples, doped with PF₅, diminished as the concentration of this gas in the plasma was increased. However, the optical gap of p-type samples, doped with BF₃, did not show any appreciable optical gap decrease as the concentration of BF₃ was varied from 0.04% to 4.7%. The dark conductivity of the p-type films at these extremes of the doping range were 7.6 × 10⁻¹⁰ and 3.5 × 10⁻¹ Ω⁻¹ cm⁻¹, respectively.     

Synthesis and electrochromic behavior of lithium-doped WO3 films

The electrochromic properties of amorphous peroxotungsten films prepared via the sol–gel route were determined. By means of the addition of LiCF₃SO₃ to the precursor solutions, films with different electrochemical properties were obtained. The electrochromic properties of the films were investigated using in situ spectroelectrochemical method and impedance measurements in propylene carbonate (PC) with 0.1 M LiClO₄ as electrolyte. During the cathodic polarization at −0.7 V, a blue color was observed with a reversible variation between 25% and 80% of the transmittance in the visible and near infrared range in the 5 mol% doped film. It reached a maximum cathodic charge density of 8 mC/cm². The bleaching process in the lithium-doped films was complete, whereas in the films without Li⁺, a residual color was observed. The impedance response of the WO₃ films showed the influence of the doping level on the electronic conduction and ionic transport of Li⁺ through the films.     

Growth of laser single-crystals Er:YVO4 by floating zone method

High optical quality Er³⁺:YVO₄ laser crystals have been grown by using the floating zone method (FZ). The spectroscopic properties and 3 μm lasing of Er³⁺:YVO₄ were investigated. It is found that the Er³⁺ concentration has a negative effect on the emission of the transition ⁴I_13/2→⁴I_15/2(1.55 μm ), and a positive effect on that of the ⁴I_11/2→⁴I_13/2 transition (2.68 μm). With direct upper-state pumping and a plane-concave cavity a self-terminating laser was achieved at the wavelength of 2.724 μm in the 30 at% Er³⁺ doped sample.     

Growth of InP in chemical beam epitaxy with high purity tertiarybutylphosphine

InP layers were grown by chemical beam epitaxy (CBE) using high purity thermally precracked tertiarybutylphosphine (TBP) and trimethylindium (TMI) as the source of the group III element. For optimized substrate temperature and V/III ratio, InP films of good electrical and optical quality have been obtained; the n-type background carrier concentration is (1–2) × 10¹⁵ cm^-3, with a Hall mobility at 77 K being μ₇₇ = 45,000 cm² V^-1 s^-1. Given the low value of the V/III ratio, and according to mass spectrosc measurements, the phosphorus species giving rise to epitaxy is expected to be the dimer P₂. The TBP consumption in CBE is very low when compared to organometallic vapour phase epitaxy (OMVPE), typicaly below 0.25 g/μm of InP layer.     

Laser precipitation of SnO2 nanocrystals in glass and energy transferred-fluorescence of Eu ions

SnO₂ nanoparticles having an average particle size of 5 nm were precipitated in a transparent glass by irradiation with an 800 nm femtosecond laser. Glass was prepared to co-dope Sn⁴⁺ and Eu³⁺ ions by a sol–gel method, followed by heating in H₂ gas atmosphere to form the Sn⁰₂ point defects with a molecular-like electronic structure in the twofold-coordinated Sn atoms. Upon laser irradiation, the Sn⁰₂ defects react with oxygen, forming SnO₂ nanocrystals. When excited at the energy corresponding to the absorption edge of the SnO₂ nanocrystals, the energies, which are absorbed by the quantum-dot effect in the nanosized crystals, are efficiently transferred to the Eu³⁺ ions, resulting in the large enhanced fluorescence intensities from the Eu³⁺ ions. The observed phenomenon suggests application to high-density memory devices.     

Formation of LiNbO3 films by hydrolysis of metal alkoxides

Homogeneous, crack-free, thin films of crystalline LiNbO₃ were synthesized above 250°C on Si(100) substrates by the dip-coating method using a double alkoxide solution. The coating solution, which was prepared by the controlled partial hydrolysis of the double alkoxide, gave stoichiometric LiNbO₃ crystalline films at temperatures as low as 250°C. The concentration of the alkoxide solution influenced both of thickness and quality of films. Crystallinity of thin film top-coated directly on the substrate affected the crystallization state of films coated on the film remarkably. Films crystallized on -Al₂O₃(0001) showed preferred orientation along the c-axis, while the preferred orientation could not be observed on Si(100) substrates.     

Hexagonal AlN films grown on nominal and off-axis Si(0 0 1) substrates

Nucleation and growth of wurtzite AlN layers on nominal and off-axis Si(0 0 1) substrates by plasma-assisted molecular beam epitaxy is reported. The nucleation and the growth dynamics have been studied in situ by reflection high-energy electron diffraction. For the films grown on the nominal Si(0 0 1) surface, cross-sectional transmission electron microscopy and X-ray diffraction investigations revealed a two-domain film structure (AlN¹ and AlN²) with an epitaxial orientation relationship of [0 0 0 1]_AlN || [0 0 1]_Si and AlN¹ || AlN² || [1 1 0]_Si. The epitaxial growth of single crystalline wurtzite AlN thin films has been achieved on off-axis Si(0 0 1) substrates with an epitaxial orientation relationship of [0 0 0 1]_AlN parallel to the surface normal and 0 1 1 0_AlN || [1 1 0]_Si.     

不同形貌TiO2薄膜的可控制备及其光电化学性能研究

采用水热法在FTO(fluorine-doped tin oxide)基底上制备不同形貌的锐钛矿结构TiO₂薄膜。通过不断增大反应前驱物中盐酸浓度,TiO₂薄膜由球状颗粒薄膜逐渐演变生长成大面积高能(001)面裸露的TiO₂纳米片阵列薄膜。通过对形貌演化规律及X射线衍射图谱变化规律进行分析,提出了不同形貌TiO₂薄膜的生长演化机制,并对盐酸在其中的作用进行了说明。为了进一步改善TiO₂薄膜的性能,采用连续离子层吸附反应法对不同形貌的TiO₂薄膜进行CdS量子点敏化。采用紫外可见吸收光谱分析法和三电极体系对复合薄膜的光吸收性能和光电化学(PEC)性能进行了研究,实验数据显示CdS/TiO₂复合薄膜的光电化学性能皆明显优于单纯TiO₂薄膜,而且纳米片阵列薄膜的性能明显优于其他形貌薄膜,说明了大面积高能(001)面裸露的TiO₂纳米片阵列薄膜的性能优越性。     

Growth and properties of (Pb0.90La0.10)TiO3 thick films prepared by RF magnetron sputtering with a PbO buffer layer

The (Pb_0.90La_0.10)TiO₃ [PLT] thick films (3.0 μm) with a PbO buffer layer were deposited on the Pt(1 1 1)/Ti/SiO₂/Si(1 0 0) substrates by RF magnetron sputtering method. The PLT thick films comprise five periodicities, the layer thicknesses of (Pb_0.90La_0.10)TiO₃ and PbO in one periodicity are fixed. The PbO buffer layer improves the phase purity and electrical properties of the PLT thick films. The microstructure and electrical properties of the PLT thick films with a PbO buffer layer were studied. The PLT thick films with a PbO buffer layer possess good electrical properties with the remnant polarization (P_r=2.40 μC cm⁻²), coercive field (E_c=18.2 kV cm⁻¹), dielectric constant (ε_r=139) and dielectric loss (tan δ=0.0206) at 1 kHz, and pyroelectric coefficient (9.20×10⁻⁹ C cm⁻² K⁻¹). The result shows the PLT thick film with a PbO buffer layer is a good candidate for pyroelectric detector.