Energy, Environment and Water Research Center, The Cyprus Institute, P,O, Box 27456, 1645, Nicosia, Cyprus.
Nanoscale Res Lett. 2009 Sep 3;4(12):1475-80. doi: 10.1007/s11671-009-9423-6.
Nowadays, organic solar cells have the interest of engineers for manufacturing flexible and low cost devices. The considerable progress of this nanotechnology area presents the possibility of investigating new effects from a fundamental science point of view. In this letter we highlight the influence of the concentration of fullerene molecules on the ultrafast transport properties of charged electrons and polarons in P3HT/PCBM blended materials which are crucial for the development of organic solar cells. Especially, we report on the femtosecond dynamics of localized (P2at 1.45 eV) and delocalized (DP2at 1.76 eV) polaron states of P3HT matrix with the addition of fullerene molecules as well as the free-electron relaxation dynamics of PCBM-related states. Our study shows that as PCBM concentration increases, the amplified exciton dissociation at bulk heterojunctions leads to increased polaron lifetimes. However, the increase in PCBM concentration can be directly related to the localization of polarons, creating thus two competing trends within the material. Our methodology shows that the effect of changes in structure and/or composition can be monitored at the fundamental level toward optimization of device efficiency.
如今，有机太阳能电池引起了工程师们的兴趣，因为它们可以制造出灵活且低成本的设备。该纳米技术领域的显著进展为从基础科学角度研究新效应提供了可能性。在这封信件中，我们强调了富勒烯分子浓度对 P3HT/PCBM 混合材料中带电电子和极化子超快输运性质的影响，这对于有机太阳能电池的发展至关重要。特别是，我们报告了在富勒烯分子的添加下，P3HT 基质中局域（P2at 1.45 eV）和离域（DP2at 1.76 eV）极化子态的飞秒动力学以及与 PCBM 相关的自由电子弛豫动力学。我们的研究表明，随着 PCBM 浓度的增加，在体异质结中放大的激子解离导致极化子寿命增加。然而，PCBM 浓度的增加可以直接与极化子的局域化相关，从而在材料中产生两种竞争趋势。我们的方法表明，可以在基本水平上监测结构和/或组成变化的影响，以优化器件效率。
