【作者】 邹业；

【导师】 邓振波；

【作者基本信息】 北京交通大学 ， 光学工程， 2012， 博士

【摘要】 本论文主要研究了有机小分子太阳能电池的器件结构对电池的光电响应特性及衰减曲线的影响。通过合理设计器件结构或控制薄膜生长方式,可以制备出具有更高光电转换效率或具有更高稳定性的有机小分子太阳能电池。具体研究内容包括：1、研究了光激活层中体异质结的厚度、体异质结结构的共掺浓度梯度变化以及基片加热技术对基于AlPcCl/C60异质结的有机小分子太阳能电池的光电响应特性的影响。研究发现：①合理控制体异质结的厚度能够优化电池的转换效率。保持光激活层的总厚度不变,当体异质结超过一定厚度的时候,虽然电池对外输出的短路电流能够继续提高,但由于器件内部的串联电阻持续增加,使得电池的填充因子不断减小,并导致器件的转换效率下降。②390K基片温度下生长AlPcCl薄膜能够有效提高基于AlPcCl/C60平面异质结结构的电池外量子效率,通过紫外/可见/红外吸收光谱、XRD衍射分析、AFM表面形貌分析等测试分析,我们认为,器件外量子效率的提高主要源自390K基片温度下生长的AlPcCl薄膜发生结晶且AlPcCl分子呈平行于基片的方向平躺排布,有利于提高器件内部的载流子输运效率；390K基片温度下生长的AlPcCl薄膜表面粗糙度增加,有利于提高光生激子的利用和解离效率。③体异质结结构的共掺浓度梯度变化辅以基片加热技术,电池能够获得更高的功率转换效率。一方面,采用体异质结共掺浓度梯度变化,使得体异质结结构器件在原具有的高激子解离效率的基础上,自由载流子复合的几率被抑制,光生载流子传输平衡性被显著提升；另一方面,体异质结结构制备过程中辅以基片加热技术,异质结薄膜发生结晶且AlPcCl分子呈现规则排布,降低了器件内部的串联电阻及提高了电池的载流子输运。2、研究了有机小分子太阳能电池的衰减规律。分别研究了采用Mo03阳极缓冲层、采用不同的TCTA给体厚度、以及采用MoO3掺杂α-NPD给体的结构对电池的衰减性能的影响。研究发现：①M003阳极缓冲层的使用,能够极大的抑制持续稳定的光照工作下电池的衰减。紫外/可见/红外吸收光谱、XRD衍射谱、AFM薄膜表面形貌分析等技术表明,M003阳极缓冲层的使用对AlPcCl薄膜的成膜方式及表面形貌没有发生明显的改变,不是导致器件衰减的主要原因；XPS薄膜表面成分分析表明,ITO电极中的氧成分扩散至有机光激活层中,是导致电池衰减的重要原因之一,MoO3阳极缓冲层的使用在一定程度上抑制了ITO电极中的氧向有机层的扩散。热刺激电流分析技术表明,器件内部的载流子聚集也是导致小分子太阳能电池衰减的重要原因之一。②增加TCTA给体的厚度容易降低器件的转换效率,但他同时能提高器件的稳定性。结合前一小节的研究结果,我们推测随着给体厚度的增加,电池的衰减受到抑制的可能原因之一是,ITO中的氧成分向有机光激活层中扩散并对电池产生衰减的作用对于给体/受体接触界面或C60受体内部有重要影响,增加给体的厚度能够降低氧成分向给体/受体接触界面或C60受体内部的扩散速度,从而降低器件的衰减。③在MoO3掺杂α-NPD的结构与受体材料之间再加入一层薄的有机给体层,既能保持器件具有较高的光电转换效率,又能获得更高的器件稳定性。可能的原因之一是MoO3掺杂α-NPD的结构使得薄膜内部产生电荷传输复合物[MoO3-:α-NPD+],有利于提高器件内部的载流子输运效率；同时,M003的应用有效抑制了ITO电极中的氧成分向光激活层中扩散。④此外,我们在试验中还发现,BCP阴极缓冲层的使用会导致器件额外的衰减。3、研究了基于AlPcCl/C60异质结的多叠层结构有机小分子太阳能电池。我们设计了合理的子电池于子电池之间的中间连接电极BCP/Ag/MoO3的结构,在五叠层结构的电池中,我们获得了3.50V之高的天路电压和2.49%的转换效率,对应的单异质结结构的电池,开路电压和转换效率分别在0.72-0.80V及1.83-2.17%的范围；在十叠层结构的电池中,我们获得了5.89V之高的天路电压。我们采用文献介绍的方法模拟了多叠层结构电池的内部光电场强度分布,并通过理论计算优化了叠层结构电池的内部结构,例如,在三叠层结构电池中,理论计算优化的结果是,器件仅通过微小的给体和受体厚度的改变,就可提高约37%的电流输出。我们期待制备的高开路电压的多叠层电池能在无面积限制且低功耗的光电子器件中得到直接运用。图62幅,表14个,参考文献267篇。更多还原

【Abstract】 This work focus on the efficiency enhancement and/or initial degradation properties of small-moleculue organic solar cells (OSCs). By optimizing OSCs device structure or control the evaporation condition of organic thin films, we can get higher power conversion efficiency (PCE) and/or higher operational stability of OSCs. Some of the interesting results have been obtained as follows.1. The effect of bulk-heterojunction thickness of photoactive layer, grade structure of bulk-heterojunction and substrate heating technology on the photovoltaic properties of small-molecule OSCs based on Aluminum phthalocyanine chloride (AlPcCl) as donor and C6o as acceptor has been systematicly studied. We found that PCE of OSCs can be enhanced by using bulk-heterojunction structure within an optimized thickness. While continuesly enhanced the bulk-heterojunction thickness, the series resistance of OSCs would also increase obviously which lead to a decreased PCE of the OSCs. By heating the substrate to390K during AlPcCl thin film evaporation, the quantum efficiency and PCE of AlPcCl/C6o planar heterojunction can be effectively improved, which is attributed to higher charge carrier transport efficiency inside the OSCs though a face-on molecule orientation of AlPcCl moleculars and a more effective exciton separation efficiency via a rougher surface of390K evaporated AlPcCl films. By heating the substrate to390K during grade structrure of AlPcCl:C60bulk heterojunction evaporation,we obtain significantly enhanced PCE of AlPcCl/C6o heterojunction OSCs, from about-2%to3.1%.2. The initial degradation properties of small-molecule OSCs under continue illumination has been investigated systematically. The impact of MoO3hole extraction buffer layer,4,4’,4"-tri(N-carbazolyl)triphenylamine (TCTA) donor layer thickness, and MoO3-doped4,4’-bis[N-(1-napthyl)-N-phenyl-amino] biphenyl (a-NPD) on the initial degradation properties of OSCs have been investigated. We found that by using MoO3as a hole extraction buffer layer, the degradation properties of OSCs under continuous illumination can be greatly inhibited. After a systematical ananlisis though UV/vis/NIR absorption, XRD, AFM and HOMO-level measurements, we found that MoO3buffer layer has no impact on film morphology of AlPcCl donor layer which was exluded to be the origin of degradation. We confirm from XPS measurement results that MoO3buffer layer has great effect on inhibiting the oxygen diffusion from ITO to organic active layer, which is suggested to be one of the important mechanisms for the OSCs. degradation. Although increasing TCTA donor layer thickness decreases PCE of OSCs, it can lead to an obviously improved stability of the device. We suppose that the diffused oxygen from ITO anode has great effect on donor/acceptor interface or C60acceptor bulk layer, which lead to the degradation. While increasing the donor layer thickness, the diffuse of oxygen from ITO anode would be partly inhibited inside donor layer. Inserting a thin layer of α-NPD between doped MoO3:α-NPD structure and C60acceptor layer can approach higher device stability without significantly decreasing the PCE of the OSCs based on a-NPD/C6o heterojunction structure. In addition, we found that BCP electron extraction buffer layer would also lead to OSCs degradation.3. OSCs based on AlPcCl as donor and C60as acceptor with a multi-tandem structure were fabricated. We demonstrated very high open-circuit voltage (Voc) and enhanced power conversion efficiency (PCE) for the multi-tandem OSCs though the using of effective BCP/Ag/MoO3intermediate connecting electrode layer. By using fivefold structure, we obtained a PCE of2.49%with a high VOC of3.50V, in comparison with PCE of-2%and Voc of0.72-0.81V for the single device. Further, we fabricated a tenfold stacked OSC showing an extremely high VOC of5.89V. The internal optical electrical field distribution inside the multi-tandem OSCs has been simulated. We also optimized the cell performance though a series theoretical calculation. The multi-tandem OSCs with very high Voc are suggested to provide potential application in area-limited low-power electronics.更多还原