Virkki Kirsi, Tervola Essi, Medel Maria, Torres Tomás, Tkachenko Nikolai V
Laboratory of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, FI-33101 Tampere, Finland.
Departamento de Química Orgánica, Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid, Spain.
ACS Omega. 2018 May 7;3(5):4947-4958. doi: 10.1021/acsomega.8b00600. eCollection 2018 May 31.
Understanding the primary processes of charge separation (CS) in solid-state dye-sensitized solar cells (DSSCs) and, in particular, analysis of the efficiency losses during these primary photoreactions is essential for designing new and efficient photosensitizers. Phthalocyanines (Pcs) are potentially interesting sensitizers having absorption in the red side of the optical spectrum and known to be efficient electron donors. However, the efficiencies of Pc-sensitized DSSCs are lower than that of the best DSSCs, which is commonly attributed to the aggregation tendency of Pcs. In this study, we employ ultrafast spectroscopy to discover why and how much does the aggregation affect the efficiency. The samples were prepared on a standard fluorine-doped tin oxide (FTO) substrates covered by a porous layer of TiO nanoparticles, functionalized by a Pc sensitizer and filled by a hole transporting material (Spiro-MeOTAD). The study demonstrates that the aggregation can be suppressed gradually by using co-adsorbates, such as chenodeoxycholic acid (CDCA) and oleic acid, but rather high concentrations of co-adsorbate is required. Gradually, a few times improvement of quantum efficiency was observed at sensitizer/co-adsorbate ratio Pc/CDCA = 1:10 and higher. The time-resolved spectroscopy studies were complemented by standard photocurrent measurements of the same sample structures, which also confirmed gradual increase in photon-to-current conversion efficiency on mixing Pc with CDCA.
了解固态染料敏化太阳能电池（DSSC）中电荷分离（CS）的主要过程，尤其是分析这些初级光反应过程中的效率损失，对于设计新型高效光敏剂至关重要。酞菁（Pc）是潜在有趣的敏化剂，在光谱的红端有吸收，并且已知是有效的电子供体。然而，Pc敏化DSSC的效率低于最佳DSSC，这通常归因于Pc的聚集倾向。在本研究中，我们采用超快光谱来探究聚集为何以及在多大程度上影响效率。样品制备在标准的氟掺杂氧化锡（FTO）衬底上，该衬底覆盖有TiO纳米颗粒的多孔层，用Pc敏化剂进行功能化，并填充有空穴传输材料（Spiro-MeOTAD）。研究表明，通过使用共吸附剂，如鹅去氧胆酸（CDCA）和油酸，可以逐渐抑制聚集，但需要相当高浓度的共吸附剂。逐渐地，在敏化剂/共吸附剂比例Pc/CDCA = 1:10及更高时，观察到量子效率提高了几倍。时间分辨光谱研究通过对相同样品结构的标准光电流测量得到补充，这也证实了将Pc与CDCA混合时光子到电流转换效率的逐渐增加。
