Zimmermann Jochen, Mulet Roberto, Scholes Gregory D, Wellens Thomas, Buchleitner Andreas
Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Str. 3, 79104 Freiburg, Germany.
J Chem Phys. 2014 Nov 14;141(18):184104. doi: 10.1063/1.4901336.
Materials capable to perform upconversion of light transform the photon spectrum and can be used to increase the efficiency of solar cells by upconverting sub-bandgap photons, increasing the density of photons able to generate an electron-hole pair in the cell. Incoherent solar radiation suffices to activate upconverters based on sensitized triplet-triplet annihilation, which makes them particularly suited for this task. This process requires two molecular species, sensitizers absorbing low energy photons, and emitters generating higher frequency photons. Successful implementations exist in solutions and solids. However, solid upconverters exhibit lower efficiency than those in solution, which poses a serious problem for real applications. In the present work, we suggest a new strategy to increase the efficiency of sensitized upconverters that exploits the solid nature of the material. We show that an upconversion model system with molecules distributed as clusters outperforms a system with a random distribution of molecules, as used in current upconverters. Our simulations reveal a high potential for improvement of upconverter systems by exploring different structural configurations of the molecules. The implementation of advanced structures can push the performance of solid upconverters further towards the theoretical limit and a step closer to technological application of low power upconversion.
能够进行光上转换的材料可改变光子光谱，并可通过对亚带隙光子进行上转换来提高太阳能电池的效率，从而增加能够在电池中产生电子 - 空穴对的光子密度。非相干太阳辐射足以激活基于敏化三重态 - 三重态湮灭的上转换器，这使其特别适合此项任务。此过程需要两种分子物种，即吸收低能光子的敏化剂和产生更高频率光子的发射体。在溶液和固体中均有成功的实例。然而，固体上转换器的效率低于溶液中的上转换器，这给实际应用带来了严重问题。在本工作中，我们提出了一种利用材料的固体性质来提高敏化上转换器效率的新策略。我们表明，分子以团簇形式分布的上转换模型系统优于当前上转换器中使用的分子随机分布的系统。我们的模拟揭示了通过探索分子的不同结构构型来改进上转换器系统的巨大潜力。先进结构的实现可将固体上转换器的性能进一步推向理论极限，并更接近低功率上转换的技术应用。
