The conversion of low-energy photons into radiation of higher energy is useful for bioimaging, 3D displays and other applications. In particular, upconversion of the infrared portion of the solar spectrum, which is typically not absorbed by the light-harvesting materials used in solar technologies, allows additional photons to be harnessed and boosts the efficiency of photovoltaic and photocatalytic devices. Therefore, low power photon upconversion of non-coherent light based on sensitized triplet-triplet annihilation (sTTA) has been recently recognized as a potential viable approach towards enhancing the efficiency of sunlight-powered devices through sub-bandgap photon harvesting. The sTTA permits the conversion of light into radiation of higher energy involving a sequence of photophysical processes between two moieties, respectively a light harvester/triplet sensitizer and an annihilator/emitter. High up-conversion yields under solar irradiance can be observed in low viscosity solutions of dyes, but in solid materials, which are better suited for integration in devices, the process is usually less efficient. The ability to control triplet excitons in the solid state is therefore crucial to obtain high performance solid upconverters. In this chapter, we will discuss the results obtained in several systems, such as dye-doped polymers/nanoparticles, amorphous/crystalline supramolecular structures and many others, highlighting the materials design guidelines to obtain efficient upconverters at the solid state that can match the strict requirements of solar technologies.
Monguzzi, A. (2022). Photon Upconversion Based on Sensitized Triplet-Triplet Annihilation (sTTA) in Solids. In J. Sandby Lissau, M. Madsen (a cura di), Emerging Strategies to Reduce Transmission and Thermalization Losses in Solar Cells Redefining the Limits of Solar Power Conversion Efficiency (pp. 49-70). Springer [10.1007/978-3-030-70358-5_4].
Photon Upconversion Based on Sensitized Triplet-Triplet Annihilation (sTTA) in Solids
Monguzzi, A
2022
Abstract
The conversion of low-energy photons into radiation of higher energy is useful for bioimaging, 3D displays and other applications. In particular, upconversion of the infrared portion of the solar spectrum, which is typically not absorbed by the light-harvesting materials used in solar technologies, allows additional photons to be harnessed and boosts the efficiency of photovoltaic and photocatalytic devices. Therefore, low power photon upconversion of non-coherent light based on sensitized triplet-triplet annihilation (sTTA) has been recently recognized as a potential viable approach towards enhancing the efficiency of sunlight-powered devices through sub-bandgap photon harvesting. The sTTA permits the conversion of light into radiation of higher energy involving a sequence of photophysical processes between two moieties, respectively a light harvester/triplet sensitizer and an annihilator/emitter. High up-conversion yields under solar irradiance can be observed in low viscosity solutions of dyes, but in solid materials, which are better suited for integration in devices, the process is usually less efficient. The ability to control triplet excitons in the solid state is therefore crucial to obtain high performance solid upconverters. In this chapter, we will discuss the results obtained in several systems, such as dye-doped polymers/nanoparticles, amorphous/crystalline supramolecular structures and many others, highlighting the materials design guidelines to obtain efficient upconverters at the solid state that can match the strict requirements of solar technologies.
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