Singlet Fission and Triplet Transfer to PbS Quantum Dots in TIPS-Tetracene Carboxylic Acid Ligands

Abstract

Singlet exciton fission allows for the generation of two triplet excitons for each photon absorbed within an organic semiconductor. Efficient harvesting of these triplets could allow for the Shockley-Queisser limit on the power conversion efficiency of single-junction photovoltaics to be broken. Here, we show that singlet fission molecules bound directly to PbS quantum dots as ligands can undergo singlet fission with near unity efficiency and can transfer triplets sequentially into the PbS with near unity efficiency. Within the PbS, the excitations recombine, giving rise of the emission of photons. This allows for the doubling of the quantum dot photoluminescence quantum efficiency when photons are absorbed by the singlet fission ligand, as compared to when directly absorbed in the quantum dot. Our approach demonstrates that it is possible to convert the exciton multiplication process of singlet fission into a photon multiplication process and provides a new path to harness singlet fission with photovoltaics.

High Photon Upconversion Efficiency with Hybrid Triplet Sensitizers by Ultrafast Hole‐Routing in Electronic‐Doped Nanocrystals

“…Triplet excitons are common in organic semiconductors, but generally inherently difficult to access because they involve spin‐forbidden electronic transitions. Nevertheless, thanks to the recently improved ability to manage spin–flip processes, [ 1,2 ] triplet excitons have been receiving significantly increased attention for their potential application in solar technologies, [ 1 ] as in the case of photon upconversion (UC) systems based on sensitized triplet–triplet annihilation (sTTA). [ 3,4 ] By sTTA, upconverted photons are generated by the radiative decay of fluorescent singlet states obtained through the fusion after collision of optically dark triplets of two annihilator molecules (often referred to also as emitters).…”

Excimer Formation in Carboxylic Acid-Functionalized Perylene Diimides Attached to Silicon Dioxide Nanoparticles

“…Recently, there has been an increase in research into the field of chromophore ligands attached to nanocrystal quantum dots 56−59 or semiconductor scaffolds, 60 in particular, the replacement of ligands that offer colloidal stability with ones that add additional optoelectronic properties. These ligands have potential applications for increased solar absorption, efficient transport of excitations, upconversion, and singlet fission.…”

High‐Yield Generation of Triplet Excited States by an Efficient Sequential Photoinduced Process from Energy Transfer to Singlet Fission in Pentacene‐Modified CdSe/ZnS Quantum Dots

“…[9] The other important point includes the far narrower fluorescences pectralr egions than those of organic dye molecules. They are thereby one of good candidates fora ne nergy donor becauseq uantum dots are easy to prepare organic-inorganic hybrid materials [10] that utilize the functionalg roups of an organic dye, such as carboxylic [11] and thiol groups. [6, 10c, 12] According to the Fçrster energy-transfer theory,t he rate constant of the energy-transfer process is proportional to the spectral overlap between the emissiono ft he donor and absorption of the acceptor and to the inverse sixth powerofthe distance betweent he donor and acceptori napoint-to-point approximation.…”