Molecular design of transmitters for efficient photon upconversion using semiconductor nanocrystals

• Grant number: 22/06470-8
• Support Opportunities: Generation Project Research Grant
• Start date: January 01, 2024
• End date: December 31, 2028
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: Brener Rodrigo de Carvalho Vale
• Grantee: Brener Rodrigo de Carvalho Vale
• Host Institution: Instituto de Física Gleb Wataghin (IFGW). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Associated researchers: Lázaro Aurélio Padilha Junior
• Associated scholarship(s): 24/01722-4 - Molecular design of transmitters for efficient photon upconversion using semiconductor nanocrystals, BP.GR

Abstract

Photophysical processes such as singlet fission and triplet-triplet annihilation (TTA) can be efficient approaches to decrease the thermalization and transmission processes, respectively, in photovoltaic devices. Conversion of low-energy photons into high-energy ones, processes called upconversion, using incoherent light at low intensities, can be performed by storing the energy into molecular long-lived excited states. Thus, a higher energy state can be achieved by triplet energy transfer (TET), which is the same mechanism as TTA. Colloidal semiconductor nanocrystals (SNCs) have a low-lying energy singlet and triplet, which makes them very attractive to triplet sensitization. Besides, SNCs have many other attributes such as size-dependent emission and absorption spectra, high photoluminescence quantum yield, and high absorption coefficient. Triplet-triplet annihilation upconversion (TTA-UC) quantum yield started from 0.01% in 2015, nowadays, the best result is 18%. To increase this efficiency, it is necessary a molecular design approach for the transmitters, the molecule responsible for the TET process. Therefore, this project aims to develop a transmitter molecular design on the nanocrystal surface to obtain high rates of TTA and efficient photon upconversion yield. The project has four branches aligned with the same main goal. The first one is focused on the effect of functional groups of native ligands of SNCs and different functional groups of transmitters. In this approach will be studied two compositions of SNCs, such as CsPbX3 (X = Cl, Br, and I) and CIS. The second branch will be focused on the aromaticity, the position of the functional group, and the multidentate group effect. Here, two morphologies of SNC will be studied and two compositions; CsPbX3 and CdSe. While the third one consists of installing an experimental setup for time-resolved fluorescence measurements with a time resolution of ~200 fs and a broad wavelength range covering the entire visible spectrum. Finally, the fourth one is dedicated to studying the effect of the functional group of ligands and transmitters on the charge carrier trapping in CIS QDs using ultrafast x-ray absorption spectroscopy. In summary, this project will allow the development of organic/inorganic interface comprehension as well as the charge transfer process at the interface, contributing to more efficient photovoltaic devices. (AU)