Photochemistry of P3HT and PC60BM in toluene solution: Evidence of T–T energy transfer

• Photochemistry of P3HT/PC60BM mixture in toluene was studied by laser flash photolysis.
• Excitation of the mixture leads to energy transfer from polymer triplet state to fullerene.
• Quantum yields of polymer and fullerene triplet state formation were estimated.
• No evidence of electron transfer from P3HT triplet state to PC60BM was observed.

Photochemical properties of regioregular poly(3-hexylthiophene) (P3HT), fullerene derivative [6,6]-phenyl C61-butyric acid methyl ester (PC60BM) and their 1:1 mixture in argon-saturated toluene solution were studied by optical spectroscopy and nanosecond laser flash photolysis (λex = 532 nm). Separate excitation of components leads to formation of corresponding triplet state of fullerene (3PC60BM*, λmax = 710 nm, ϵmax = 22400 M−1 cm−1, φT = 0.29) and polymer (3P3HT*, λmax = 850 nm, ϵ750 nm ≤ 105 M−1 cm−1, φT ≥ 0.19). Excitation of P3HT/PC60BM mixture leads to effective energy transfer from 3P3HT* to the ground state of fullerene with a formation of 3PC60BM*. No evidence of ion-radical P3HT+ and PC60BM− formation was obtained though electron transfer between 3P3HT* and 1PC60BM is energetically favorable in studied system. Presumably ultrafast back electron transfer takes place in geminate P3HT+/PC60BM− pair with regeneration of the ground states of P3HT and PC60BM.

Figure optionsDownload as PowerPoint slide