Device engineering of non-fullerene organic photovoltaics with extrapolated operational T80 lifetime over 45,000 h in air

Abstract

The efficiency and stability of organic solar cells (OSCs) is often restricted by the metastable photoactive and charge transport layers. Here, we report the acquiring of stable photovoltaics via vacuum-assisted thermal annealing (VTA), which not only enhances the molecular packing of donor and acceptor but also restrains the over-growth of photovoltaic molecules and leads to a slender fibrillar network, resulting in enhanced charge transport and suppressed carrier recombination. In situ ellipsometry measurements reveal that VTA can remove the trapped solvents and reduce the free volume of the photoactive layer, leading to slower structural relaxation during operation and therefore superior morphological and operational stability. As a result, the VTA-treated D18:L8-BO and PM6:L8-BO OSCs exhibit superior PCEs of 19.7% and 19.2%, respectively, with an ITO/PEDOT:PSS/active layer/PDINN/Ag structure, and a PCE of 18.0% with a T80 lifetime of 45,200 h for the ITO/MoO3/PM6:L8-BO/C60/BCP/Ag-structured device, corresponding to an unprecedented lifetime of 30 years.