Photon Upconversion through Triplet-Triplet Annihilation: Towards Higher Efficiency and Solid State Applications
Doctoral thesis, 2016

The sun is the only renewable energy source that can accommodate humanity’s energy needs today and in the foreseeable future. The sunlight reaching the planet’s surface is filtrated through the atmosphere, reducing its UV-light intensity in the 300-400 nm range, which indeed can be harmful to life as we know it in too large doses. However, many useful photoreactions require in practice such high-energy UV-photons, like the catalytic splitting of water to oxygen and hydrogen gas or molecular in-bond energy storage through isomerization to produce heat when reverting to the initial state. The efficiency of these applications could be improved with efficient conversion of low-energy visible to high-energy UV-light. One way to achieve this type of photon upconversion (UC) is through the process called Triplet-Triplet Annihilation (TTA) relying on the interaction between two molecules; a sensitizer and an annihilator. The sensitizer absorbs low energy visible photons as input and transfers that energy through Triplet Energy Transfer (TET) to an annihilator. Two triplet-excited annihilators can thereafter perform TTA, merging the energy equivalents of the two low-energy photons to produce one high-energy photon as output. This Thesis is focused on improving the known bimolecular UC system in fluid environment and approaching the ultimate goal of high efficiency UC in solid materials. In the fluid system I demonstrate the employment of thiol- and thioether-based compounds as scavengers for singlet excited oxygen with positive effect on UC efficiency and stability. In an attempt to aid future design and optimization of upconversion system components the anthracene is 9,10-substituted with electron withdrawing or donating groups while its TTA-UC function is evaluated revealing that substitution at para-positions leads to least perturbation of its spectroscopic properties. The ultimate goal is to achieve supramolecular TTA-UC systems capable of efficient intra-molecular TET and TTA processes and unhindered emission of the upconverted photons. As a first step, we focus on the intra-molecular TTA process with oligomers and dendrimers of 9,10-diphenylanthracene (DPA) which display positive effects on UC efficiency in solid matrix. In the second step the focus is on the intra-molecular TET process where the sensitizer-annihilator complexes are explored through Lewis base-acid coupling with orthogonal transition moments for minimum excited state short circuit effect. Additionally, kinetic simulations of the TTA-UC processes are conducted to aid understanding and optimization. Finally, one TTA-UC system is also applied to chemical in-bond energy storage.

solar energy conversion

triplet-triplet annihilation

energy transfer

fluorescence anisotropy

anti-stokes

photon upconversion

excited state

porphyrins

photochemistry

photophysics

delayed fluorescence

dendrimers

anthracene

oligomers

spectroscopy

KA-salen, Kemigården 4, Chalmers University of Technology, Göteborg
Opponent: Prof. Jacek Waluk, Department of Photochemistry and Spectroscopy, Institute of Physical Chemistry, Polish Academy of Sciences, Poland

Author

Damir Dzebo

Chalmers, Chemistry and Chemical Engineering, Chemistry and Biochemistry

Conjugated anthracene dendrimers with monomer-like fluorescence

RSC Advances,; Vol. 4(2014)p. 19846-19850

Journal article

Porphyrin-Anthracene Complexes: Potential in Triplet-Triplet Annihilation Upconversion

Journal of Physical Chemistry C,; Vol. 120(2016)p. 19018-19026

Journal article

Triplet-triplet annihilation photon-upconversion: Towards solar energy applications

Physical Chemistry Chemical Physics,; Vol. 16(2014)p. 10345-10352

Review article

Photon upconversion facilitated molecular solar energy storage

Journal of Materials Chemistry,; Vol. 1(2013)p. 8521-8524

Journal article

Intramolecular Triplet-Triplet Annihilation Upconversion in 9,10-Diphenylanthracene Oligomers and Dendrimers

Journal of Physical Chemistry C,; Vol. 120(2016)p. 23397-23406

Journal article

Dagens teknik för uppsamling av solenergi, så som solceller, fungerar oftast bäst med en specifik ljusfärg men om man på något sätt kunde få dem att fånga upp fler färger skulle de bli mer effektiva. Jag har jobbat med att omvandla grönt ljus till mer energirikt blått ljus med hjälp av molekyler. En ”antenn-molekyl” fångar upp en grön ljuspartikel och överför den till en ”omvandlar-molekyl” som har förmågan att slå ihop två gröna ljuspartiklar och ge ifrån sig den sammanlagda energin i form av en blå ljuspartikel. Om en film med dessa molekyler skulle sättas på en solcell som tar upp blått ljus skulle den fånga upp mer av solens energi då hela systemet kan ta upp både blåa och gröna ljuspartiklar. I min forskning har jag undersökt möjligheten att sätta ihop ”antenn-molekylen” med ”omvandlar-molekylen” för att få energiöverföringen mellan dem att bli mer effektiv och fungera även i fasta material. Detta är viktigt eftersom energiöverföringen störs av syremolekyler som finns i luften runtom oss. Jag visar även ett annat sätt att lösa problemet i vätska genom att använda syre-fångande molekyler istället för det mer bökiga sättet att pumpa ut syremolekyler ur vätskan. Den forskning jag gjort har bidragit med viktig information för det fortsatta arbetet med att göra energiutvinning från solen mer effektivt. Förhoppningsvis kommer vi snart fram till en bra lösning som kan ge våra barn och efterkommande generationer en mer hållbar och klimatsmartare energiutvinning.

Driving Forces

Sustainable development

Innovation and entrepreneurship

Areas of Advance

Nanoscience and Nanotechnology (SO 2010-2017, EI 2018-)

Energy

Materials Science

Subject Categories

Physical Chemistry

Chemical Sciences

Roots

Basic sciences

ISBN

978-91-7597-420-0

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie

KA-salen, Kemigården 4, Chalmers University of Technology, Göteborg

Opponent: Prof. Jacek Waluk, Department of Photochemistry and Spectroscopy, Institute of Physical Chemistry, Polish Academy of Sciences, Poland

More information

Created

10/8/2017