Influence of static disorder of charge transfer state on voltage loss in organic photovoltaics

Spectroscopic measurements of charge transfer (CT) states provide valuable insight into the voltage losses in organic photovoltaics (OPVs). Correct interpretation of CT-state spectra depends on knowledge of the underlying broadening mechanisms, and the relative importance of molecular vibrational broadening and variations in the CT-state energy (static disorder). Here, we present a physical model, that obeys the principle of detailed balance between photon absorption and emission, of the impact of CT-state static disorder on voltage losses in OPVs. We demonstrate that neglect of CT-state disorder in the analysis of spectra may lead to incorrect estimation of voltage losses in OPV devices. We show, using measurements of polymer:non-fullerene blends of different composition, how our model can be used to infer variations in CT-state energy distribution that result from variations in film microstructure. This work highlights the potential impact of static disorder on the characteristics of disordered organic blend devices. Charge transfer state provides insight into energy loss in organic photovoltaics, which is dictated by molecular vibrations and static disorder. Here, the authors propose a method for exploring the effect of donor/acceptor interface microstructure on charge transfer state characteristics and device performance.

Automated summary

Charge transfer state provides insight into the energy loss in organic photovoltaics, influenced by molecular vibrations and static disorder. The authors propose a method for exploring the effect of donor/acceptor interface microstructure on charge transfer state characteristics and device performance.