Degradation through Directional Self?Doping and Homogeneous Density of Recombination Centers Hindered by 1,8?Diiodooctane Additive in Non?Fullerene Organic Solar Cells

Non-fullerene-based organic solar cells (OSCs) have recently proven to perform with efficiencies above 18%. This is an important milestone for one of the most promising technologies in fields flexible and transparent/semitransparent photovoltaics. However, stability OSCs still a challenging issue meet industry requirements. Herein, several devices IT-4F:PM6 as active layer without 1,8-Diiodooctane (DIO) additive are characterized before after 1400 h degradation test under 1 sun white light-emitting diode (LED) illumination intensity. The optoelectronic study via impedance spectroscopy at quasi-open-circuit correlates use DIO retarded behavior overall improved device performance. In dark conditions, Mott–Schottky analysis suggests that samples develop self-doping during degradation, changing p-i-n doping profile into p–n type, likely related evolution blend demixing. These mechanisms further confirmed by drift-diffusion simulations. Space-oriented redistribution shallow trap levels (self-doping) homogeneous increase deep-trap (nonradiative recombination) shown be hindered additive.