Multiexciton generation in organic materials promises to overhaul the technology of organic photovoltaics by amplifying the quantum yield of charge generation. A collaborative study led by scientists at TIFR Mumbai, JNU New Delhi and IACS Kolkata have shown that organic chromophores which do not energetically satisfy the multi-exciton generation condition can still be coaxed to carry high quantum yield energy harvesting by chemically synthesizing molecular dimers.

The molecular equivalent of multi-exciton generation in organic molecules is known as singlet fission. Singlet fission is defined as a photophysical process by which two triplet excitons can be generated in organic chromophores at the cost of one absorbed photon. However only a few classes of chromophores which have triplet energies half the singlet energy can successfully host singlet fission. In this work, the scientists show for the first time that napthalenediimide (NDI) whose triplet energies do not satisfy this criteria, can still harvest triplets via singlet fission due to construction of a highly contorted novel NDI dimer.

These results have now been published in the journal Chemical Science. The TIFR group includes graduate student Mr. Arup Kundu and Prof. Jyotishman Dasgupta from the Department of Chemical Sciences.