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Probing surface and internal nanostructures and electrical properties of organic solar cell materials.

机译：探测有机太阳能电池材料的表面和内部纳米结构以及电性能。

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摘要

Polymer:fullerene bulk heterojunction solar cells have been the subject of intense research since their discovery more than 10 years ago. The polymer:fullerene bulk heterojuction is the most efficient organic device structure due to the intimate contact between the hole (polymer) and electron (fullerene) transporting materials throughout the bulk. The morphology of the bicontinuous networks affects exciton separation, carrier transport, charge recombination, and energy conversion efficiency of the bulk device. Despite the popularity of bulk heterojuction devices, probing the morphology of the donor and acceptor networks, both at the surface of the blended film and throughout the interior of the bulk heterojuntion, has proven to be a challenge. To image the internal networks of the films, we developed a method to prepare a cross section of the bulk heterojunction device and subsequently studied it using phase imaging atomic force microscopy. The cross section was fabricated by focused ion beam and placed on an indium tin oxide (ITO) coated glass substrate for imaging. To measure the nanoscale carrier mobilities through the thickness of the film, we used conductive atomic force microscopy (C-AFM). In C-AFM, the conducting tip acts as a nanoelectrode and is able to measure the electrical properties of regions approximately 10 nm in diameter. C-AFM measures current as a function of applied voltage either at specific points on a surface or maps out the current image. We selectively probed the hole (donor) or electron (acceptor) transporting networks by controlling the work functions of the substrate and the conducting tip. By taking a large number of mobility measurements at different locations across the surface of the film, we were able to determine the homogeneity of the film's electrical properties. In addition to measuring mobilities, this technique in current imaging mode was used to identify surface structures as being composed of either hole or electron transporting material. Coupled with an inverted optical microscope, nanoscale photocurrent images and I-V curves can be obtained that help to understand the charge generation process and surface morphology.;The above techniques were used to study several different systems, including poly(3-hexylthiophene) (P3HT):[6,6]-phenyl C61-butyric acid methyl ester (PC 61BM) and poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']-dithiopene)- alt-4,7-(2,1,3-bezothiadiazole)] (PCPDTBT):[6,6]-phenyl C71-butyric acid methyl ester (PC71BM) bulk heterojunctions, and P3HT- b-P(S89BAz11)-C60, a rod-coil block copolymer composed of a P3HT block and fullerene containing block. The effect of processing conditions on the surface and internal morphology and on the charge transport characteristics of the film were studied. The processing conditions examined included thermal annealing, the use of solvent additives, and film casting technique. In general, it was found that these processing techniques can have a large impact on the morphology of the donor and acceptor networks of the device, which in turn can dramatically affect the ability of free carriers to move through the film, and thus on the overall energy conversion efficiency of the device.
机译：自从十多年前发现聚合物：富勒烯本体异质结太阳能电池以来，一直是人们研究的热点。聚合物：富勒烯本体异质结是最有效的有机器件结构，这是因为空穴（聚合物）和电子（富勒烯）传输材料在整个本体中的紧密接触。双连续网络的形态会影响激子分离，载流子传输，电荷复合以及大容量器件的能量转换效率。尽管本体异质结器件的普及，在混合薄膜的表面以及本体异质结的整个内部探测供体和受体网络的形态已被证明是一个挑战。为了对薄膜的内部网络成像，我们开发了一种制备体异质结器件截面的方法，随后使用相成像原子力显微镜对其进行了研究。通过聚焦离子束制造横截面，并将其放置在氧化铟锡（ITO）涂层的玻璃基板上进行成像。为了测量贯穿薄膜厚度的纳米级载流子迁移率，我们使用了导电原子力显微镜（C-AFM）。在C-AFM中，导电尖端充当纳米电极，并且能够测量直径大约10 nm的区域的电性能。 C-AFM在表面的特定点处测量电流或施加电压的函数，或者绘制出当前图像。我们通过控制衬底和导电尖端的功函数，有选择地探测了空穴（施主）或电子（受主）的传输网络。通过在整个薄膜表面的不同位置进行大量的迁移率测量，我们能够确定薄膜电性能的均匀性。除了测量迁移率外，该技术在当前成像模式下还被用来识别表面结构是由空穴还是电子传输材料组成。结合倒置光学显微镜，可获得纳米级光电流图像和IV曲线，有助于了解电荷产生过程和表面形态。上述技术用于研究多种不同的系统，包括聚（3-己基噻吩）（P3HT） ：[6,6]-苯基C61-丁酸甲酯（PC 61BM）和聚[2,6-（4,4-双-（2-乙基己基）-4H-环戊[2,1-b; 3， 4-b']-二噻吩）-alt-4,7-（2,1,3-bezothiadiazole）]（PCPDTBT）：[6,6]-苯基C71-丁酸甲酯（PC71BM）本体异质结和P3HT -bP（S89BAz11）-C60，一种由P3HT嵌段和含富勒烯的嵌段组成的棒-线圈嵌段共聚物。研究了加工条件对薄膜表面和内部形貌以及薄膜电荷传输特性的影响。检查的加工条件包括热退火，使用溶剂添加剂和薄膜流延技术。通常，发现这些处理技术会对设备的供体和受体网络的形态产生很大影响，进而会极大地影响自由载流子穿过薄膜的能力，从而对整个薄膜产生影响。设备的能量转换效率。

著录项

  • 作者

    Dante, Mark.;

  • 作者单位

    University of California, Santa Barbara.;

  • 授予单位 University of California, Santa Barbara.;
  • 学科 Chemistry Physical.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 195 p.
  • 总页数 195
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

  • 入库时间 2022-08-17 11:38:20

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