有机太阳能电池给体材料设计合成与器件优化研究

发布时间：2018-01-14 02:16

本文关键词：有机太阳能电池给体材料设计合成与器件优化研究　出处：《南开大学》2014年博士论文　论文类型：学位论文

【摘要】：本论文设计并合成了一系列新型有机太阳能电池的给体材料,并对它们的热稳定性、吸收光谱、电化学性能和固态堆积状态进行了测试,同时详细研究了它们作为电子给体材料在有机太阳能电池中的光电转换性能。为了进一步提高有机小分子太阳能电池的能量转换效率,我们将研究重点转移至器件优化和机理研究。首先使用各种不同的电子传输层,将DR3TBDT作为给体材料的小分子太阳能电池的能量转换效率提高至8.32%。然后通过制备并优化翻转结构的器件,将以DRCN7T作为给体材料的翻转结构小分子太阳能电池的能量转换效率提高至8.84%。在上面的合成及器件优化过程中,我们对光电转换机理和器件寿命进行了初步的研究。最后我们基于本组在过去四年中理论计算方面的结果,对分子结构设计和性能预测提出了一些观点和看法。具体各部分内容摘要如下：一、设计并合成了两个具有相同骨架但侧链不同的异硫茚(ITN)和苯并双噻吩(BDT)的新型醌式交替共聚物PBDT-DEAITN和PBDT-DOAITN,并研究了它们的光电转换性能。这两个聚合物有非常窄的光学带隙,分别为1.52和1.58eV。将它们与PC61BM共混后制备的器件,在标准太阳光下的能量转换效率分别是1.25%和1.20%。通过薄膜X射线衍射和原子力显微镜测试观察到这两个聚合物在固体状态下堆积较差,同时用空间电荷限制电流测试得到两个聚合物都有较低的迁移率；通过理论计算优化对应聚合物单体的结构,发现PBDT-DEAITN和PBDT-DOAITN中相邻异硫茚和苯并双噻吩单元之间的二面角分别高达33.66°和34.35°,较大的二面角会导致较差的堆积和低的迁移率,进而导致低的能量转换效率。通过理论计算的二面角和偶极矩结果分析,发现给体材料具有平面性骨架有利于得到更高的光电转换性能。基于此,分子的平面性成为本组设计给体分子的重要参考依据。二、为了获得更高的开路电压,我们设计并合成了三个带有不同端基的寡聚五噻吩衍生物DCAO5T,DERHD5T和DIN5T,并将这三个给体分子分别与富勒烯衍生物进行共混制备有机太阳能电池器件,测试了其在标准太阳光下的光电转换性能。其中,基于DERHD5T的器件获得了1.08V的开路电压和4.63%的能量转换效率,这是有机太阳能电池中为数不多的开路电压可以超过1V的给体材料。同时DCAO5T和DIN5T分别获得了3.27%和4.00%的能量转换效率,开路电压分别为0.88V和0.78V。通过理论模拟研究了高开路电压的原因,发现DERHD5T与PC61BM之间的电子偶合能力最弱,从而降低了器件的反向饱和电流密度,使得开路电压有一定的提高,理论预测的开路电压和实验的结果趋势一致。上述结果证明,除了通过降低给体HOMO能级(或者提高受体材料的LUMO能级)来提高器件开路电压外,削弱给体与受体之间的电子偶合也是非常重要的途径。三、为了提高有机太阳能电池的能量转换效率,制备了基于DR3TBDT:PC71BM作为活性层的小分子太阳能电池,分别使用聚芴衍生物(PFN)、氧化锌纳米颗粒和氟化锂作为电子传输层,得到的能量转换效率分别为8.32%、7.30%和7.38%。其中,基于PFN的能量转换效率是目前基于苯并双噻吩体系小分子太阳能电池的最高效率。论文详细研究了引入不同的电子传输层对器件性能影响的原因,发现引入PFN后,能量转换效率明显提高的原因是减少了器件中的双分子复合,同时增加了活性层的有效吸光。四、在上述器件优化工作的基础上,我们制备了基于DRCN7T:PC71BM作为活性层的翻转结构小分子太阳能电池,在标准太阳光照射下,器件的能量转换效率为8.84%,对应的开路电压为0.91V,短路电流密度为14.28mA cm-2,填充因子为0.68,这也是目前基于翻转结构小分子太阳能电池的世界纪录。在相同条件下制备的正常结构器件,开路电压和填充因子没有明显变化,能量转换效率为8.06%,短路电流密度为13.07mA cm-2.通过变光强实验证实了正常结构和翻转结构器件中,电荷的复合机制基本接近,因此后者短路电流密度增加的原因主要是增加了活性层的有效吸光,这也与光学模拟的结果一致。经过封装后,制备的翻转结构器件在空气中存放103天后,器件的能量转换效率仍然在8%以上,显示了小分子太阳能电池具有良好的发展前景。五、本章比较了各种泛函和基组在光电功能材料预测方面的优点与缺点,发现B3LYP/6-31G*和PBE1PBE/6-31G*基本可以满足有机半导体的结构优化、HOMO能级、吸收光谱和电荷传输重组能等参数的预测。尤其是PBE1PBE/6-31G*的结果与实验结果吻合的较好。基于Marcus电子转移方程,我们将理论计算得到的给体空穴重组能与对应器件能量转换效率进行关联,发现给体分子的空穴重组能越小,越有利于给体与受体界面的激子分离和给体中空穴的传输与收集,进而得到更高的能量转换效率。这对以后的光电分子设计具有重大的指导意义。
[Abstract]:This paper designed and synthesized a series of novel organic solar cell material, and the thermal stability of their absorption spectra, electrochemical properties and solid state accumulation were tested, and studied them as a photoelectric conversion electron donor material in organic solar cell performance. In order to further improve the energy conversion efficiency of organic small molecular solar cells, we will study the focus to the device optimization and mechanism research. First, using a variety of different electron transport layer, DR3TBDT as the energy conversion efficiency was improved to 8.32%. for small molecule solar cell materials and devices through the preparation and optimization of flip structure, with DRCN7T as synthesis and device the optimization process to the turnover structure of small molecule material solar energy conversion efficiency was improved to 8.84%. in the above, we on the photoelectric The mechanism of conversion and the lifetime of devices have been preliminarily studied. Finally, based on the results of theoretical calculations in the past four years, we put forward some viewpoints and opinions on molecular structure design and performance prediction.
A design, and two have the same skeleton but isothianaphthene different side chains were synthesized (ITN) and benzo (BDT) thiophene double novel quinone alternating copolymer PBDT-DEAITN and PBDT-DOAITN, and studied their photoelectric conversion properties. These two polymers have very narrow optical band gap, respectively 1.52 and they will be 1.58eV. and PC61BM in the blends prepared in the standard device, the sun's light energy conversion efficiency were 1.25% and 1.20%. thin films by X ray diffraction and atomic force microscopy observed the two polymer poor accumulation in the solid state, at the same time with the space charge limited current test two polymers have migration low rate; through theoretical calculation and optimization structure of the corresponding polymer monomer, PBDT-DEAITN and PBDT-DOAITN found that the dihedral angle between adjacent isothianaphthene and benzo bithiophene units were as high as 33.66 degrees and 34.35 degrees, The larger dihedral angle will lead to poor accumulation and low mobility, which leads to low energy conversion efficiency. Through the theoretical calculation and analysis of the dihedral angle and the dipole moment results, found that donor materials with planar skeleton to obtain higher photoelectric conversion performance. Based on this, the plane of the divided sub group to design an important reference molecule.
Two, in order to obtain a higher open circuit voltage, we design and three different end groups with oligomeric five thiophene derivatives synthesized by DCAO5T, DERHD5T and DIN5T, and the three donor molecules respectively and fullerene derivatives were prepared by blending organic solar cell device, the photoelectric conversion in the standard sun performance test. The DERHD5T device based on 1.08V was obtained in the open circuit voltage and energy conversion efficiency of 4.63%, which is the organic solar cell open circuit voltage for a few more than 1V to the bulk material. The energy conversion efficiency at DCAO5T and DIN5T respectively won the 3.27% and 4%, respectively 0.88V and 0.78V. open circuit voltage study on the causes of high open circuit voltage through theoretical simulation, found between DERHD5T and PC61BM of the electronic coupling weakest, thereby reducing the device reverse saturation current density, the open circuit voltage is To some extent, the results of theoretical and experimental prediction of open circuit voltage of the same trend. The results show that, except by reducing the donor HOMO level (or increase the LUMO level of receptor materials) to improve the device open circuit voltage, weaken the way to electronic coupling between the donor and acceptor is also very important.
Three, in order to improve the energy conversion efficiency of organic solar cells, DR3TBDT:PC71BM were prepared as small molecular solar cells based on the active layer, respectively using polyfluorene derivatives (PFN), Zinc Oxide nano particles and lithium fluoride as an electron transport layer, the energy conversion efficiency were 8.32%, 7.30% and 7.38%., PFN energy conversion efficiency is the highest efficiency based on benzo bithiophene system of small molecular solar cells based on the reasons. This paper made a detailed research into the influence of different electron transport layer on the device performance, found that after the introduction of PFN, significantly improve the efficiency of energy conversion reason is to reduce the double molecular devices in the composite, while increasing the effective absorption activity layer.
Four, based on the optimization of the device, we prepared the turnover structure of small molecular solar cells DRCN7T:PC71BM as active layer based on the standard in the sunlight, the energy conversion efficiency of the device is 8.84%, the open circuit voltage corresponding to the 0.91V, the short-circuit current density was 14.28mA cm-2, the fill factor of 0.68 and the is currently the turnover structure of small molecular solar cells based on the world record. The normal structure of devices prepared under the same conditions, the open circuit voltage and the fill factor did not change significantly, the energy conversion efficiency of 8.06%, short circuit current density of 13.07mA cm-2. by changing the light intensity experiment confirmed the normal structure and turning structure device, the basic mechanism of composite charge close, so the reason for the latter to increase the short circuit current density is mainly to increase the effective absorption of the active layer, this also with the optical simulation results. After packaged, The energy conversion efficiency of the device is still more than 8% after storing for 103 days in air, showing that the small molecule solar cell has good prospects for development.
Five, this chapter compares the various functionals and basis sets in photoelectric materials forecast the advantages and disadvantages of B3LYP/6-31G* and PBE1PBE/6-31G* can meet the basic structure optimization, organic semiconductor HOMO level, prediction of absorption and charge transfer reorganization energy and other parameters. Especially the PBE1PBE/6-31G* results and the experimental results agree well with the Marcus. Based on the equation of electron transfer, we will give the calculated body hole reorganization energy and corresponding device energy conversion efficiency of the association, found that recombinant molecules can hole smaller, more conducive to the exciton separation donor and acceptor interface and to transmit and collect in the hole, and then get the higher energy conversion efficiency. Is of great significance to the photoelectric molecular design in the future.

【学位授予单位】：南开大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM914.4

【共引文献】