An intermediate band dye-sensitised solar cell using triplet–triplet annihilation

Abstract

A new mechanism of charge photogeneration is demonstrated for the first time, based on organic molecular structures. This intermediate band approach, integrated into a dye-sensitised solar cell configuration is shown to generate charges upon illumination with low energy photons. Specifically 610 nm photoexcitation of Pt porphyrins, through a series of energy transfer steps and triplet-triplet annihilation, excites a higher energy absorption onset molecule, which is then capable of charge injection into TiO2. Transient absorption measurements reveal further detail of the processes involved.

Efficient triplet–triplet annihilation upconversion in binary crystalline solids fabricated via solution casting and operated in air

“…Triplet-triplet annihilation upconversion (TTA-UC) is an emerging technology for converting low-energy photons into higher-energy ones with light intensities close to that of sunlight, [1][2][3][4][5][6][7] which has potential uses in photovoltaic devices [8][9][10] and photocatalysis. 11,12 For these purposes, solid TTA-UC systems are preferable, so a number of efforts have been devoted to the development of solid systems such as doped polymers 13,14 and gels.…”

Green to Blue Annihilated Upconversion from a Simple Iridium(III) Sensitizer with Carboxylic Group

“…Triplet‐triplet annihilation (TTA) with multi‐chromophores system comprising a triplet sensitizer and an acceptor is an effective approach to generating upconverted fluorescence using low‐power laser (<100 mW/cm 2 , equal to the sunlight), which was firstly demonstrated by Parker and Hatchard in 1962 and has significant applications so far, such as photovoltaics, photocatalysis and bioimaging . According to the revealed mechanism, TTA‐upconversion undergoes a series of multiple quantum processes: (i) the sensitizer first absorbs one photon to the excited singlet state and goes across its triplet excited state by intersystem crossing (ISC); (ii) then, the triplet–triplet energy transfer (TTET) occurs from the sensitizer to the acceptor, and then two triplet acceptors undergo the triplet‐triplet annihilation (TTA) with the result that photon‐upconversion is produced.…”

Limiting efficiencies for intermediate band solar cells with partial absorptivity: the case for a quantum ratchet

“…Optical transitions from the RB to the VB are considered to be forbidden by symmetry and/or spatial separation of electronic wavefunctions. An example of a naturally occurring QR is dyes used for molecular upconversion solar cells , which have recently also been employed directly in IBSCs . Even though the ratchet step introduces an energy loss, such a QR configuration drastically reduces radiative recombination and can thereby increase the efficiency of an IBSC in the radiative limit .…”