Sohoni Siddhartha, Ghosh Indranil, Nash Geoffrey T, Jones Claire A, Lloyd Lawson T, Li Beiye C, Ji Karen L, Wang Zitong, Lin Wenbin, Engel Gregory S
Department of Chemistry, The University of Chicago, Chicago, IL, USA.
The Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL, USA.
Nat Commun. 2024 Sep 27;15(1):8280. doi: 10.1038/s41467-024-52341-2.
Photon absorption is the first process in light harvesting. Upon absorption, the photon redistributes electrons in the materials to create a Coulombically bound electron-hole pair called an exciton. The exciton subsequently separates into free charges to conclude light harvesting. When two excitons are in each other's proximity, they can interact and undergo a two-particle process called exciton-exciton annihilation. In this process, one electron-hole pair spontaneously recombines: its energy is lost and cannot be harnessed for applications. In this work, we demonstrate the creation of two long-lived excitons on the same chromophore site (biexcitons) at room temperature in a strongly coupled H-aggregated zinc phthalocyanine material. We show that exciton-exciton annihilation is suppressed in these H- aggregated chromophores at fluences many orders of magnitudes higher than solar light. When we chemically connect the same aggregated chromophores to allow exciton diffusion, we observe that exciton-exciton annihilation is switched on. Our findings demonstrate a chemical strategy, to toggle on and off the exciton-exciton annihilation process that limits the dynamic range of photovoltaic devices.
光子吸收是光捕获的第一步。吸收光子后，光子会在材料中重新分布电子，从而形成一个由库仑力束缚的电子 - 空穴对，即激子。激子随后分离成自由电荷，完成光捕获过程。当两个激子彼此靠近时，它们会相互作用并经历一个称为激子 - 激子湮灭的双粒子过程。在这个过程中，一个电子 - 空穴对会自发复合：其能量损失，无法用于应用。在这项工作中，我们展示了在室温下，在强耦合的H聚集酞菁锌材料中，在同一发色团位点上产生两个长寿命激子（双激子）。我们表明，在这些H聚集发色团中，激子 - 激子湮灭在比太阳光高许多数量级的光通量下受到抑制。当我们化学连接相同的聚集发色团以允许激子扩散时，我们观察到激子 - 激子湮灭被开启。我们的发现展示了一种化学策略，用于开启和关闭限制光伏器件动态范围的激子 - 激子湮灭过程。
