【作者】 郑巧；

【导师】 方国家；

【作者基本信息】 武汉大学 ， 凝聚态物理， 2013， 博士

【摘要】 本论文首先研究了热退火对基于一种新型窄带隙聚合物作为有机太阳能电池给体材料时器件的光电性能的影响；然后重点介绍了三种石墨烯杂化材料的制备、性能表征和它们在聚合物太阳能电池中的应用；最后介绍了如何利用液晶小分子提高聚合物太阳能电池能量转换效率方面的工作。具体内容如下：1.窄带隙聚合物作为给体材料的工作一种新型的窄带隙聚合物：环戊烯并二噻吩/噻吩酰亚胺(简称P1)取代光敏层中常见的聚3-己基噻吩(P3HT)作为聚合物太阳能电池的电子给体材料,研究热退火对P1:PCBM (C60的衍生物)混合薄膜的影响,重点探讨了基于P1:PCBM为光敏层的电池器件在不同温度退火后电池的光电性能。研究表明不经过热退火处理的电池性能最优,能量转换效率(PCE)为2.01%,Jsc,Voc和FF分别是5.97mA/cm2,0.86V和39%。利用单载流子器件测量载流子的迁移率后发现,电池经过退火后,虽然电子和空穴的迁移率都上升,但是由于电子和空穴迁移率之间的不平衡性被进一步扩大,产生空间电荷区,所以退火之后虽然吸光强度增大但仍然导致短路电流下降。从电池的能带结构分析发现,由于给体材料P1的HOMO与PCBM的LUMO之间的能量差为1.3eV,所以电池能够得到0.86V的高开路电压。2.石墨烯杂化物作为受体材料的工作用简单的水热法制备了石墨烯/氧化锌的杂化材料(简称G-ZnO),对G-ZnO材料的形貌、成分组成、晶体结构、光、电学性质做了系统表征,并将其作为电子受体材料制备了聚合物太阳能电池。重点研究了电池性能与光敏层中G-ZnO含量的关系。随着光敏层中G-ZnO含量的增加,电池的PCE先增加后降低。当G-ZnO占光敏层总质量(G-ZnO的质量加上P3HT的质量)的15%时,P3HT的晶粒大小为16.6nm左右,满足激子扩散和分离的条件,电子迁移率达到1.32×10-5cm2V-1s-1,同时电池的串联电阻Rs也达到最小值,此时电池的PCE为0.98%,V。c为0.81V,Jsc为4.92mA/cm2。3.石墨烯杂化物作为空穴传输层的工作利用水热法制备了一种氧化石墨烯的衍生物——钼离子修饰的氧化石墨烯(GO-Mo),并对GO-Mo薄膜的成分、形貌、晶体结构、表面化学态、霍尔迁移特性做了系统表征。GO-Mo薄膜具有良好的透光性,在波长为400-800nm范围内透光率超过90%。Hall测试结果表明其为P型半导体,载流子浓度为～1013cm-3, GO-Mo薄膜的载流子迁移率达到10.8cm2V-1s-1。制备了GO-Mo作为空穴传输层(简称HTL)的聚合物太阳能电池,PCE能达到2.61%,Jsc,Voc和FF分别为9.02mA/cm2、0.59V和49%,与传统的PEDOT:PSS为HTL时的PCE相当。最后还研究了不同层数的GO-Mo薄膜对电池性能的影响,由于3层的GO-Mo薄膜能够形成连续的电荷传输通道,所以此时电池的PCE最大。4.石墨烯杂化物作为阳极的工作通过水热法制备了石墨烯(简称G)和ATO (SnO2:Sb)纳米颗粒的复合物ATO/Go讨论了退火温度和退火环境对ATO/G薄膜的透光性和导电性的影响,并用ATO/G薄膜取代ITO作为电池的阳极制备了聚合物太阳能电池。ATO/G薄膜具有良好的光学透光性,在300-800nm范围内的透光率超过了90%,但是方块电阻在兆欧以上,通过牺牲薄膜透光率的方式能够降低了薄膜的方块电阻。当ATO/G薄膜在热退火后,方块电阻有一定程度的下降,并且发现在空气中的退火效果要比在Ar气中的退火效果好。为了进一步降低薄膜的方块电阻,用磁控溅射的方法在ATO/G薄膜的表面镀上10nm厚的Au,最后利用ATO/G/Au薄膜作为阳极,制备了结构为ATO/G/Au/MoO3/P3HT:PCBM/Al的聚合物太阳能电池,PCE达到1.85%。5.利用液晶小分子修饰界面提高电池光电转换效率的工作为了提高电池的PCE,把一种盘状的液晶小分子材料——六丁氧苯并菲(简称HAT4)插入空穴传输层和光敏层之间,其中空穴传输层采用了三种不同的材料。当HTL为PEDOT:PSS时,PCE提高43%；当HTL为M003时,PCE提高43%；当HTL为NiO时,PCE提高35%。讨论了利用HAT4使电池PCE提高的微观物理机制,当电池经过150℃退火后,HAT4会形成有序的六角柱状相,柱内分子电子云的相互交叠形成了一个准一维的电荷传输通道,电荷沿着柱的轴线方向传递,有效地提高了电池中载流子的迁移率从而使Jsc上升,同时研究发现HAT4薄膜的厚度对器件的PCE也有着重要的影响。更多还原

【Abstract】 Firstly, the thermal annealing effects on a novel low band-gap polymer and related polymer solar cells (PSCs) have been attentively investigated in this dissertation. Secondly, the synthetic methods of three graphene hybrid are introduced and the photoelectric properties and their applications on PSCs of these products are checked out and studied systematacially. Lastly, we introduced a method to improve the power conversion efficiency (PCE) of the PSCs by inserting a liquid crystal molecule thin layer.1. A novel low band-gap polymer as the donor in the PSCsA novel low band-gap polymer poly [(4,4-bis(2-ethyl)cyclopenta-[2,1-b:3,4-b’] dithiophene)-2,6-diyl-alt-(5-octylthieno[3,4-b]pyrrole-4,6-dione)-1,3-diyl](PCPDTTP D, P1) is used to replace P3HT as the donor material to blend with PCBM. The roles of the thermal annealing on the structure and properties of P1:PCBM films and the performances of the PSCs are investigated. The best performance is obtained in the device without annealing. The value of Jsc, Voc and FF is5.97mA/cm2,0.86V and39%respectively, resulting in the maximum PCE of2.01%. Hole and electron mobilities increase after heat treatment compared to those of devices without annealing. The values of Jsc of the cells decrease as a result of the unbalance enhancement in the charge conduction of the thermal annealed P1:PCBM layer. The energy level offset between the HOMO of P1and the LUMO of P3HT is1.3eV. Thus, a Voc as high as0.86V is obtained for this type of PSCs.2. Graphene hybrid as the acceptor in the PSCsGraphene-Zinc Oxide (G-ZnO) nanocomposites are prepared through hydro thermal approach and used as the electron acceptors in poly-(3-hexylthiophene)(P3HT)-based bulk heterojunction OSCs. The morphology, chemical composition, crystal structure and photoelectric properties of G-ZnO are investigated. The blended film which is a mixture of different weight ratio of P3HT and G-ZnO is applied as the active layer in the OSCs device. The PCE increases first and then decreases with the increase of G-ZnO content in the blended active layer. The best PCE of the device reaches to0.98%, and Voc of0.81V and Jsc of4.92mA/cm are obtained in the device with15wt%G-ZnO content (ratio to P3HT). The average crystallite size is distinctly calculated to be16.6nm in the films corresponding to15wt%G-ZnO ratio of P3HT content. This condition is favor for the diffusion and separation of the most excitons. The electron mobility reaches to1.32×10-5cm2V-1s-1in the15wt%G-ZnO blended film and the Rs reaches the lowest value, so the PCE is the maximum.3. Graphene hybrid as the hole transport layer (HTL) in the PSCsA Mo6+cation modified graphene oxide (GO) derivative of GO-Mo is synthesized by a low-temperature solution method to replace PEDOT:PSS which posesses a strong acidic nature. The composition, morphology, crystal structure, surface chemical states and Hall carrier properties are investigated systematically. The transmittance of the GO-Mo films exceeds90%at the range from400to800nm. The GO-Mo films present a p-type property with a Hall measurement and the carrier concentration is about～1013cm-3. The hole mobility of the GO-Mo film with0.1g Mo-precursor is10.8cm2V-1s-1. The best performance is obtained in the device with the HTL prepared from0.10g Mo-precursor in GO solution, which is comparable to that of using conventional PEDOT:PSS. The value of Jsc, Voc and FF is9.02mA/cm2,0.59V and49%, respectively, resulting in the maximum PCE of2.61%. The effect of the GO-Mo layer number on the device’s performance is also studied. When the layer number increases to3, the GO-Mo fragment may be enough to provide a continuous and complete interface and to form an effective charge transport pathway. Then, a great increase in the cell efficiency can be obtained.4. Graphene hybrid as the anode in the PSCsA simple and facile technique for the synthesis of ATO-graphene is proposed by using graphite oxide (GO) and ATO nanoparticles through a hydrothermal approach. The ATO/G films present good transmittance and electrical conductivity. The impact effects of different annealing temperature and atmospheres on the films are studied. The PSCs are fabricated when ATO/G is used as the anode. The transmittance of the ATO/G films exceeds92%at the range from300to800nm, but the sheet resistance is as high as MΩ. To decrease the sheet resistance, the transmittance is sacrificed. The properties of the films annealed in the air are better than that of the films annealed in Ar atmosphere. To further decrease the sheet resistance, a thin Au nanoparticle film is deposited on the surface of the ATO/G films by a magnetron sputtering system. The ATO/G films are used as the anode to fabricate the PSCs device with a structure as: ATO/G/Au/MoO3/P3HT:PCBM/Al, and the PCE reaches to1.85%.5. A liquid crystal molecule improvement the PCE of the PSCs A simple method to enhance PCE of OSCs is introduced by insertion of a discotic liquid crystalline molecule [2,3,6,7,10,11]-Hexabutoxytriphenylene (HAT4) between HTL and active layer (P3HT:PCBM). In order to further investigate how the HAT4improves the PCE of OSCs, three different p-type materials are deposited on the substrate as HTLs, including PEDOT:PSS, MoO3and NiO, respectively. Comparing with the devices without HAT4, PCE is increased by43%,43%and35%in the ones with HAT4for different HTL, respectively. The microscopic process during annealing, HAT4molecules distribute in the P3HT:PCBM blended layer changing from the discotic phase to a column phase after150℃annealing. Homeotropic alignment in columnar phases can provide a most efficient pathway for carriers along the columnar axis which is favorable for charge transport. HAT4molecules distribute in the active layer to improve the charge mobility as a result of the enhancement of Jsc. The thickness of the HAT4film takes an importance role in the performance of the cells.更多还原