The impact of reabsorption effect on composition analysis of organic semiconductors

Reabsorption is one of the most fundamental optical phenomena, but it has rarely been considered in spectroscopy-based composition analysis for organic semiconductors. Here, we take four state-of-the-art organic solar cell (OSC) materials as examples, and systematically investigate the influence of reabsorption on photoluminescence emission and excitation spectra by both experimental studies and optical simulations. We find that the overlap between absorption and emission spectra of these OSC materials is strong enough for them to be affected by the reabsorption effect, and the effect becomes more obvious between different species in the multi-components systems. Moreover, three features of the reabsorption effect and the reabsorption strength are identified, with which we have successfully analyzed the composition in a range of OSC materials in both solution and solid-state films. Our work not only provides an important understanding of the largely overlooked feature of reabsorption in the widely used spectroscopic techniques but also offers an effective toolbox for the composition analysis of organic semiconductors.