影响聚合物电致发光器件旋涂膜厚因素的研究

采用正交试验设计,应用方差分析方法,研究了旋涂工艺中聚合物溶液的浓度、匀胶机的旋涂速度和加速度以及旋涂时间对所制备的薄膜厚度的影响.试验和分析结果表明:溶液浓度和旋涂速度对薄膜厚度具有显著性的影响,而旋涂加速度和旋涂时间对它的影响则不显著.使用旋涂工艺制备聚合物薄膜时,合理选择溶液浓度和旋涂速度,对于优化器件的性能具有非常重要的作用.     

不同旋涂速率对聚合物太阳电池性能的影响

以聚3己基噻吩(P3HT)和[6,6]-phenyl-C61-butyric acid methyl ester(PCBM)为活性层材料制成聚合物太阳电池,通过控制活性层旋涂速率控制活性层厚度。从不同活性层厚度器件的吸收光谱、原子力及器件各项性能参数详细分析了不同活性层旋涂速率对太阳电池性能的影响。结果表明:旋涂速率为1 000 r/min时,电池具有最佳性能,光电转换效率最高为1.54%。     

PEDOT修饰对Ag/P3HT/ITO样品载流子注入特性的改善

通过分析Ag/P3HT/ITO结构样品的载流子注入特性,研究了PEDOT(3,4-Ethylene-dioxythiophene thiophene)的界面修饰对样品薄膜注入特性的影响,其中,P3HT(Poly(3-hexyl-thiophene))薄膜采用旋涂法制备,P3HT溶液浓度为30mg/ml(氯仿为溶剂)。测试结果表明:1)P3HT的退火温度对其本身性能影响很大,退火温度越高,导电性能越差,在373K时,性能达到最佳,单位面积电流可达0.092A/cm2;2)PEDOT的界面修饰作用使Ag与P3HT功函数不匹配的问题得到明显改善。实验结果与理论分析基本吻合,样品注入特性改善比在1.15～1.30之间。同样的样品在退火温度为373K时性能达到最佳,单位面积电流可达0.106A/cm2。     

sol-gel法制备(002)高度定向的Li:ZnO薄膜

用sol-gel法在玻璃载玻片上旋涂3~9层制备氧化锌薄膜。用X射线衍射、扫描电镜等研究了掺Li、旋涂层数、溶胶的浓度以及热处理温度对氧化锌薄膜(002)定向性的影响。结果表明,溶胶中掺入一定量的Li可显著地促进ZnO沿(002)生长;浓度为0.45mol/L旋涂3层或浓度为0.25mol/L旋涂7层的样品,即使有Li的掺入也不能呈现较好的(002)定向性,这是由于薄膜太薄所致;提高热处理温度至610℃,有利于薄膜(002)高度定向。     

有机层／阴极界面修饰对体异质结聚合物太阳能电池性能的影响

通过制备四种不同结构的器件,详细分析研究了活性层／阴极界面修饰对P3HT:PCBM聚合物体异质结太阳能电池性能的影响。当在P3HT:PCBM薄膜上旋涂一层PCBM,并蒸镀0.5 nm LiF时所制备的器件的填充因子和光电转换效率都得到较大的提高。对器件的光电性能和薄膜的形貌进行深入分析,阐明界面修饰的作用机理。     

P(VDF/TrFE)聚合物薄膜光波导的实验研究

采用棱镜耦合法和偏振反射技术研究了Ｐ（ＶＤＦ／ＴｒＦＥ）聚合物薄膜光波导特性。配制适当重量比浓度的Ｐ（ＶＤＦ／ＴｒＦＥ）溶液,通过提高极化时的温度,可制成均匀透明的极化聚合物薄膜平面波导。Ｐ（ＶＤＦ／ＴｒＦＥ）成膜后薄膜内部的晶界与晶粒对于其光学性质的影响可以获得较大改善。样品用旋涂法制备。研究了制备工艺对光学特性的影响。     

聚合物发光器件的旋涂膜厚模型研究

聚合物膜厚的控制对于优化聚合物发光器件的光电性能是至关重要的.应用最小二乘法,通过对中心复合设计实验数据的拟合,建立了旋涂法制备聚合物薄膜的膜厚回归模型.测试结果表明:利用该模型所得到的预测膜厚与旋涂的实测膜厚基本相符.膜厚模型的建立,对于旋涂工艺中旋涂条件的选择、薄膜厚度的控制以及器件性能的优化具有一定的实用价值.     

用于光波导的高性能聚合物薄膜制备工艺研究

讨论了在硅基片上旋涂用于光波导的PS聚合物薄膜时,部分工艺参数,如溶液浓度、旋涂转速、溶剂挥发性、吸水性等对薄膜质量的影响,得到了薄膜厚度随浓度和转速变化的经验公式。分析了造成薄膜缺陷的原因,并对薄膜的性能如薄膜厚度、红外吸收特性和表面轮廓进行了测试。     

表面传导电子发射显示器微细结构光刻工艺的优化

研究了旋涂和光刻工艺对制备表面传导发射显示器(SED)微细结构的影响,分析正性光刻胶和旋涂工艺的作用机理,探讨光刻胶的平面旋涂工艺、曝光剂量、前烘对光刻图形的影响.借助旋涂技术将光刻胶转移在附有金属薄膜的玻璃基片上,利用紫外光对其进行曝光,通过视频显微镜、台阶仪对实验结果分析,优化实验工艺参数.结果表明,光刻胶留膜率随旋转速度增大而减少,随光刻胶的粘度增大而增大,光刻图形宽度随曝光剂量的增大而变窄,曝光剂量40～50 mJ/cm2,前烘110 ℃保温25 min条件下光刻图形边缘平整,为研制SED微细结构奠定了基础.     

BaTiO_3压电薄膜的制备及其性能研究

利用旋涂技术,在聚二甲基硅氧烷(PDMS)混合液中掺入不同质量分数(30%,50%,70%)的钛酸钡(BaTiO_3)纳米颗粒,并将混合物均匀涂在洁净的硅片表面进行旋涂处理;加热固化制得压电薄膜,并对压电薄膜进行极化处理,分别运用扫描电子显微镜(SEM),X线衍射(XRD)仪分析薄膜表面和BaTiO_3粉末。实验结果表明,薄膜内部BaTiO_3分布相对均匀,且其中BaTiO_3纳米颗粒为四方相。设计振动能量采集测试系统测试分析薄膜的输出开路电压和供电能力,分别用单悬臂梁振动和激振器敲击的形式对压电薄膜的输出特性进行研究。压电薄膜的输出电压峰-峰值与BaTiO_3的质量分数具有高度的一致性,在w(BaTiO_3)=70%时,输出电压最高,对应的峰-峰值为3.50V。     

原子层沉积薄膜之激光损伤性能分析

采用目前尚在国内鲜有报道的原子层沉积技术在熔石英和BK7玻璃基片上镀制了TiO2单层膜、AlO3单层膜以及TiO2/Al2O3增透膜,沉积温度在110℃和280℃.利用X射线粉末衍射仪对膜层微观结构进行了分析研究,并在激光损伤平台上进行了抗激光损伤阈值的测量.采用Nomarski微分干涉差显微镜和原子力显微镜对激光损伤...     

The effect of Al electrodes on the nanostructure of poly(3-hexylthiophene): Fullerene solar cell blends during thermal annealing

The presence of Al electrodes on P3HT:PCBM blended thin films significantly modifies the structure of the films during thermal annealing processes used to produce organic photovoltaic cells. In the absence of an Al electrode, thermal annealing produces very thin (0.7 nm) P3HT layers with face-on molecular stacking near the surface of the film and vertically oriented rod-like P3HT crystals in the bulk region with edge-on molecular stacking. Thermal annealing in the presence of an Al electrode makes the preferred orientation of P3HT crystals in the films less prevalent, and Al diffuses into the organic films to form an intermediate layer. The absence of very thin P3HT layers and the less favorable P3HT orientation help to form interpenetrating networks in the organic layer, resulting in better device performance in the films annealed with Al electrodes.     

On the stability of the electrical and photoelectrical properties of P3HT and P3HT:PCBM blends thin films

New photoelectrical properties of poly(3-hexylthiophene-2,5-diyl), highly regioregular (P3HT): Methanofullerene Phenyl-C₆₁-Butyric-Acid-Methyl-Ester [60] PCBM films were putted in evidence. For the first time the electrical conductivity dependencies on temperature in dark and under different illuminations were studied for the P3HT and P3HT:PCBM blend films. These dependencies shows reversible processes and a high sensitivity of the P3HT and P3HT:PCBM to light. The decrease of the resistivity at the exposure to light is of 18% for P3HT films and of 20% for P3HT:PCBM blend films, for a irradiation under 0.5 W/m² white light at room temperature. By adding the fullerene molecules, in the 1:0.8 polymer:fullerene ratio, the electrical resistivity at room temperature of the blend films decrease compared to the polymer film by 40% in dark, and by 68% under 250 W/m² white light irradiance.The decrease of the resistivity with the temperature is more pronounced in the presence of light indicating a photon activated process.The existence of the open circuit voltage was evidenced even for planar geometry photodiodes and the values of the open circuit voltage under 1000 W/m² solar light illumination are coherent with the difference between the work functions of the electrodes.     

Correlation Between Structural and Optical Properties of Composite Polymer/Fullerene Films for Organic Solar Cells

We investigate thin poly(3‐hexylthiophene‐2,5‐diyl)/[6,6]‐phenyl C₆₁ butyric acid methyl ester (P3HT/PCBM) films, which are widely used as active layers in plastic solar cells. Their structural properties are studied by grazing‐incidence X‐ray diffraction (XRD). The size and the orientation of crystalline P3HT nanodomains within the films are determined. PCBM crystallites are not detected in thin films by XRD. Upon annealing, the P3HT crystallinity increases, leading to an increase in the optical absorption and spectral photocurrent in the low‐photon‐energy region. As a consequence, the efficiency of P3HT/PCBM solar cells is significantly increased. A direct relation between efficiency and P3HT crystallinity is demonstrated.     

The chemical and structural origin of efficient p-type doping in P3HT

We investigate the chemical and structural properties of solution-processed thin films of P3HT blended with p-type dopant F4TCNQ. The maximum in-plane electrical conductivity of doped films is observed at a molar doping fraction of 0.17, in agreement with the binding mechanism of F4TCNQ:P3HT complexes. Through the use of X-ray diffraction, a previously unreported crystalline phase is observed for P3HT films doped above a critical threshold concentration. This crystalline phase involves the incorporation of F4TCNQ molecules into ordered polymer regions and ultimately improves charge dissociation, leading to higher carrier density in thin film. Finally, optical absorption and X-ray diffraction reveal that the chemical state of P3HT in solution has a dramatic impact on the electrical and structural properties of the blended films.     

Improvement of photovoltaic performance of inverted hybrid solar cells by adding single-wall carbon nanotubes in poly(3-hexylthiophene)

Solution prepared hybrid solar cells show promising low cost technology for electricity generation from sun light, although their power conversion efficiency has to be improved. One of the approaches is to increase the absorbance or charge carrier mobility of organic semiconductors. In this work, pristine single walled carbon nanotubes (SWCNT) were added into poly(3-hexylthiophene) (P3HT) solution to form P3HT:SWCNT composite films with different weight percent (wt%) of SWCNT. It is observed that optical absorbance spectra as well as the morphology of the composite films were modified by the addition of SWCNTs. This phenomenon could be explained by the π-π interaction between the conjugated polymer and carbon nanotubes. Most importantly, the electrical conductivities of the composite films increased with the SWCNT wt%. When these films were used as hole conductor layers in inverted planar hybrid solar cell, with CdS thin films as electron acceptor layers, the fill factor (FF) and open-circuit voltage (Voc) of the corresponding cells were decreased with the increase of the wt% of SWCNT. However, the short-circuit current density (Jsc) and the power conversion efficiency (PCE) showed a maximum value at about 0.4 wt% of SWCNT in P3HT. The transient photovoltage measurements (TPV) revealed that the presence of SWNCT promoted the charge recombination process at P3HT/CdS interface, and as a result, reduced the Voc. The photovoltaic performance of the hybrid solar cells could be optimized by choosing an adequate weight percentage of SWCNT in P3HT to balance the charge carrier transport and charge recombination processes at the donor-acceptor interface.     

Nanoscale imaging of dense fiber morphology and local electrical response in conductive regioregular poly(3-hexylthiophene)

We present a thermal annealing method for producing micrometer long and dense semi-crystalline fiber structures in poly(3-hexylthiophene) (P3HT) films. The thin film topology and local electrical properties are investigated by conductive atomic force microscopy (c-AFM), and three-dimensional device models are used to illustrate the effects of current spreading, anisotropic mobility and traps. In-plane current flow along high mobility fibers provides a mechanism for c-AFM contrast in fibrous films. The comparison of c-AFM results between the annealed and non-annealed P3HT films suggests that trap effects are pronounced in disordered P3HT thin films prior to thermal annealing. The methodologies we demonstrate here on the archetypal P3HT film can be generalized for understanding the correlation between structure and local electrical properties in a variety of polymer and polymer nanocomposite systems.     

High field-effect mobility from poly(3-hexylthiophene) thin-film transistors by solvent–vapor-induced reflow

Room-temperature exposure of spin-coated poly(3-hexylthiophene) (P3HT) films to ortho-dichlorobenzene vapor increases the field-effect mobility of the P3HT organic thin-film transistors (OTFTs). The mobility increases moderately with unsaturated vapor exposure, owing to increased crystallinity of the P3HT films; on the other hand, the mobility increases abruptly with saturated vapor exposure, to 0.11 cm²/V s. The saturated vapor exposure causes the P3HT films to reflow, leaving in the active area approximately 2–3 P3HT monolayers whose molecular ordering is enhanced by the flow-generated shear against the gate dielectric. Although the reflowed OTFTs degrade in air much faster than do the non-reflowed OTFTs due to the susceptibility of the ultra-thin reflowed films, they become highly stable when encapsulated, obtaining a lifetime of more than 3000 h.     

Controlled nanorubbing of polythiophene thin films for field-effect transistors

We present results obtained by applying the nanorubbing process to improve the electrical performance of regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT) thin films. Essentially, we use a scanning atomic force microscope tip to induce a controlled deformation on the surface consisting of parallel grooves with a period imposed by the scanning parameters. The optical characterization of the rubbed zones highlights an orientation of P3HT chains along the scanning direction. When the nanorubbing process is orienting the polymer chains within the channel of a field-effect transistor, we observe that the charge carrier mobility increases (decreases) when the tip scans parallel (perpendicular) to the source–drain axis. This difference likely stems from the polymer chains orientation induced by the alignment process.     

Morphological Origin of Charge Transport Anisotropy in Aligned Polythiophene Thin Films

The morphological origin of anisotropic charge transport in uniaxially strain aligned poly(3‐hexylthiophene) (P3HT) films is investigated. The macroscale field effect mobility anisotropy is measured in an organic thin film transistor (OTFT) configuration and compared to the local aggregate P3HT mobility anisotropy determined using time‐resolved microwave conductivity (TRMC) measurements. The field effect mobility anisotropy in highly aligned P3HT films is substantially higher than the local mobility anisotropy in the aggregate P3HT. This difference is attributed to preferentially aligned polymer tie‐chains at grain boundaries that contribute to macroscale charge transport anisotropy but not the local anisotropy. The formation of sharp grains between oriented crystalline P3HT, through tie chain removal by thermal annealing the strained aligned films, results in an order of magnitude drop in the measured field effect mobility for charge transport parallel to the strain direction. The field effect mobility anisotropy is cut in half while the local mobility anisotropy remains relatively constant. The local mobility anisotropy is found to be surprisingly low in the aligned films, suggesting that the π?π stacking direction supports charge carrier mobility on the same order of magnitude as that in the intrachain direction, possibly due to poor intrachain mobility through chain torsion.