标题: | 具有在氧化钛上形成自组装单层结构及交联特性之碳六十衍生物其在反式高分子太阳能电池之应用;掺混含有五氟苯基之碳六十衍生物于稳定有机太阳能电池形貌之研究 Self-Assembled and Cross-Linked Fullerene Interlayer on Titanium Oxide for Highly Efficient Inverted Polymer Solar Cells |
作者: | 曹峯溢 Cao, Fong-Yi 郑彦如 Cheng, Yen-Ju 应用化学系分子科学硕博士班 |
关键字: | 有机太阳能电池;高分子太阳能电池;organic solar cell;polymer solar cell |
公开日期: | 2010 |
摘要: | 本论文分为两大主题,第一部分为具有在氧化钛上形成自组装单层结构及交联特性之碳六十衍生物在反式高分子太阳能电池之应用,第二部分为掺混含有五氟苯基之碳六十衍生物于稳定高分子太阳能电池形貌之研究。 第一部分:将两具有oxetane官能基修饰之碳六十衍生物- [6,6]-phenyl-C61-butyric oxetane ester (PCBO) 以及 [6,6]-phenyl-C61-butyric oxetane dendron ester (PCBOD) 引入反结构高分子太阳能电池的应用中。从表面接触角(surface contact angle)及X射线光电子能谱(XPS)的结果可发现具有中性特性的oxetane可利用加热、照光在氧化钛表面做阳离子开环反应产生键结。在修饰一个oxetane官能基的PCBO材料方面,其可与氧化钛表面-OH基团形成单层自组装结构。在反结构混掺系统元件B (ITO/TiOx/SA-PCBO(self-assembled PCBO)/P3HT:PCBM(1:1 w/w)/MoO3/Ag)效率可达到4.1%,相对于没有做任何修饰的标准元件A (ITO/TiOx/P3HT:PCBM (1:1 w/w)/MoO3/Ag)效率3.6%有明显地提升。其元件表现提升的原因在于其提升了激子拆解的效率以及降低载子再结合的机会,减少介面电阻,且由于自组装产生的键结,覆盖掉氧化钛表面的捕捉电子缺陷,因此效率有显着地提升。具有两个oxetane官能基的PCBOD,其不仅具有与氧化钛表面形成自组装的功能,且分子间会交联形成一紧密且坚固的结构。又交联的PCBOD为多分子层结构,因此其可以避免PCBO单分子结构覆盖不完全,造成缺陷的缺点,在修饰PCBOD材料的元件C(ITO/TiOx/C-PCBOD(crosslinking PCBOD) /P3HT:PCBM(1:1, in wt% )/MoO3 /Ag),其效率更高达4.5%。 第二部分:近期在有机太阳能电池元件的研究中,传统的P3HT:PCBM的混掺系统元件,其主动层形貌的热不稳定性为大家广为探讨的议题。随着对元件施加热能,主动层内具有较高分子迁移率的球状碳六十分子,会自发的扩散聚集,造成较大团簇甚至单晶结构,形成较差的相分离尺度,而此不适当的相分离尺度会影响主动层内激子的扩散及载子的传递。在我的研究中,设计一具有五氟苯基取代的碳六十衍生物-[6,6]-phenyl-C61-butyric pentafluorophenyl ester (PCBFP),将其掺入P3HT:PCBM的混掺系统中,利用五氟苯基与碳六十之间的作用力做物理性的聚合,进而巩固主动层的形貌,达到长时间热稳定的效果。在混掺系统为P3HT:PCBM:PCBFP(重量比例为6:5:1)的元件表现中,在150℃下加热25小时,其效率可高达3.7%。 This research contains two independent parts, the first part is self-assembled and cross-linked fullerene interlayer on titanium oxide for highly efficient inverted polymer solar cells, and the second part is morphological stabilization by incorporation of a pentafluoro phenyl-containing fullerene for highly stable oganic solar cells. In first part, we used two oxetane-functionalized fullerene derivatives, [6,6]-phenyl-C61-butyric oxetane ester (PCBO), and [6,6]-phenyl-C61-butyric oxetane dendron ester (PCBOD) in the inverted solar cells to achieve higher power conversion efficiency. We demonstrated that the oxetane functionality with neutral nature can anchor onto the TiOx surface via cationic ring-opening reaction under thermal and UV treatment, as evidenced by the contact angle measurement and x-ray photoelectron spectroscopy. The self-assembly of PCBO, functionalized with one oxetane group, on the TiOx surface forms an adhesive monolayer with intimate contact. Inverted bulk-heterojunction device B (ITO/TiOx/SA-PCBO/P3HT:PCBM(1:1, w/w)/MoO3/Ag) with this self-assembled PCBO (SA-PCBO) modifier showed an impressive power conversion efficiency of 4.1%, which outperforms the reference device A (PCE = 3.6%) without this monolayer (ITO/TiOx/P3HT:PCBM(1:1, w/w)/MoO3/Ag). This SA-PCBO modifier exerts multi-positive effects on the interface, including improvement of exciton dissociation efficiency, reduction of charge recombination, decrease of the interface contact resistance and passivation of the surface electron-traps at the interface of TiOx. Furthermore, PCBOD, containing two oxetane groups, is capable of self-assembling on the TiOx surface and simultaneously undergoing cross-linking, generating a dense, robust and pinhole-free multi-molecular interlayer to further strengthen the interface characteristics. Device C (ITO/TiOx /C-PCBOD/P3HT:PCBM(1:1, in wt%)/MoO3/Ag) incorporating this cross-linked PCBOD (C-PCBOD) interlayer delivered the highest PCE of 4.5% which represents 26% enhancement over device A. This simple and easy strategy smartly integrates the advantages of self-assembly and cross-linking in a single fullerene-based molecule, showing promise in producing highly efficient inverted PSCs. A primary area of concern for traditional P3HT:PC61BM system is the morphological instability. Upon heating, spherical PCBM with high molecular mobility tends to diffuse out of the P3HT matrix and aggregate into larger cluster or single crystals. Such a progressive phase-segregation eventually leads to micron-sized D-A domains with concomitant reduction of device efficiency. In the second part, we have designed a pentafluorophenyl-containing fullerene -[6,6]-phenyl-C61-butyric pentafluorophenyl ester (PCBFP) which was doped into the P3HT:PC61BM active layer to form a ternary blending system. Physical polymerization through the attractive quadrupole-quadrupole interaction between pentafluorophenyl groups and C60 core-structure was demonstrated to effectively prevent the thermal-driven phase separation. The device based on the P3HT:PCBM:PCBFP(6:5:1 in wt %) blend showed extremely stable device characteristics, delivering an average power conversion efficiency (PCE) of 3.7 % during the long-term thermal heating at 150 ℃ for 25 hours. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT079858505 http://hdl.handle.net/11536/48483 |
显示于类别: | Thesis |