Exciton-to-biexciton transition in quasi-one-dimensional organics

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Abstract
In the previous paper we demonstrated novel multiexcitons in a neutral mixed‐stack charge‐transfer solid. The lowest multiexciton, the biexciton, has recently been of interest also in the context of quasi‐one‐dimensional organic materials that are different from the mixed‐stack solids. The nature and strength of the optical transition from the exciton to the two‐exciton states is of importance in understanding photoinduced absorption as well as two‐photon absorption. We show that within the diverse theoretical models that describe these different classes of materials, the excited state absorption from the optical exciton to the two‐exciton states changes in a fundamental way upon the formation of the biexciton. The identical nature of the exciton absorption within these models is a consequence of one dimensionality.