Influence of alkyne spacers on the performance of thiophene-based donors in bulk-heterojunction organic photovoltaic cells
Influence of alkyne spacers on the performance of thiophene-based donors in bulk-heterojunction organic photovoltaic cells
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DOI：
10.1016/j.dyepig.2021.109152
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发表时间：
2021-01
影响因子：
4.5
通讯作者：
John Marques dos Santos;Marios Neophytou;A. Wiles;Calvyn T Howells;R. S. Ashraf;I. McCulloch;G. Cooke
中科院分区：
文献类型：
--
作者：
John Marques dos Santos;Marios Neophytou;A. Wiles;Calvyn T Howells;R. S. Ashraf;I. McCulloch;G. Cooke
对可再生能源日益增长的需求促使人们加强了对利用丰富的太阳能的研究。利用共轭聚合物给体材料制备的溶液处理有机太阳能电池是有机光伏发电的早期发展方向。最近，使用小分子供体制造的有机太阳能电池变得越来越有吸引力，因为这些系统比它们的聚合物对应物具有优势。这些包括可重复合成和更准确地发展结构-活性关系的能力。在这里，我们报道了基于噻吩的小分子给体的合成，并用于研究炔π-间隔剂对溶液可加工体积异质结（BHJ）有机OPV电池的光学、电子和光伏性能的影响。此外，我们比较了3,4-乙烯二氧噻吩（EDOT）单元代替这些衍生物的端噻吩的添加。我们发现含有炔基的化合物表现出较差的电荷转移和蓝移uv -可见光谱，而加入EDOT单元增加了非炔基衍生物的电荷转移，导致吸光度红移。DFT计算预测，不含炔单元的化合物具有较高的电荷分离/迁移率和较低的电荷生成。事实上，缺少炔间隔物的化合物具有更高的jscvalue和更高的pce。含有EDOT的化合物表现出较差的性能，这可能是由于不利的形态和较高的HOMO水平，导致较低的Voc。因此，最简单的5T-1分子表现出最高的3.24%的性能，是含炔的5TA-1的1.6倍，是含edot衍生物的2.9倍。本研究表明，炔间隔剂会对轨道相互作用、电荷转移和OPV性能产生不利影响，而EDOT单元由于其辅助给能，可以提供更大的电荷转移。然而，需要仔细设计，以确保更高的voc值和有利的形貌在噻吩基溶液可处理的opv。
The ever-increasing demand for renewable energy has led to the intensification of research focused upon harnessing the abundant energy from sunlight. Solution processed organic solar cells fabricated using conjugated polymer donor materials dominated the early development of organic photovoltaics (OPV). More recently, organic solar cells fabricated using small molecule donors have become increasingly attractive due to the advantages these systems have over their polymeric counterparts. These include reproducible synthesis and the ability to more accurately develop structure-activity relationships. Here, we report the synthesis of thiophene based small molecule donors that have been used to investigate the influence of alkyne π-spacers on the optical, electronic and photovoltaic properties of solution-processable bulk-heterojunction (BHJ) organic OPV cells. Additionally, we compare the addition of 3,4-ethylenedioxythiophene (EDOT) units in place of the end-thiophene of these derivatives. We found that the compounds featuring alkyne moieties displayed poor charge transfer and blue-shifted UV–vis spectra, whereas the incorporation of the EDOT units increased charge transfer for the non-alkyne derivative resulting in red-shifted absorbance. DFT calculations predicted higher charge separation/mobility and lower charge generation for the compounds without alkyne units. Indeed, greater Jscvalues and higher PCEs were found for the compounds lacking alkyne spacers. EDOT containing compounds showed poor performance which is likely due to an unfavourable morphology and higher HOMO level, leading to lower Voc. Hence, the simplest 5T-1 molecule showed the highest performance of 3.24%, which is c.a. 1.6x that of the alkyne-containing 5TA-1 and c.a. 2.9x that of the EDOT-containing derivative. This study demonstrates that alkyne spacers can be detrimental to orbital interactions, charge transfer and OPV performance, and that the EDOT unit can be added to provide greater charge transfer due to its auxiliary donating ability. However, careful design is required to ensure higher Vocvalues and a favourable morphology in thiophene-based solution-processable OPVs.