Introduction of co-additives to form well dispersed photoactive layer to improve performance and stability of organic solar cells

•4-Fluorobenzaldehyde used as co-additives in the fullerene and non-fullerene systems.•Co-additives allowed the formation of a well-distributed molecular order.•Co-additives formed more favorable structure for charge transport.•Co-additives maintained the phase by preventing aggregation.•The device with co-additives exhibit more stable at ambient atmosphere conditions. We fabricated organic solar cells (OSCs) based on bulk-heterojunction photoactive layers with fullerene (PTB7:PC71BM) and non-fullerene (PBDB-T:ITIC) systems by introducing 1,8-diiodooctane (DIO) and 4-fluorobenzaldehyde (4-FBA) as co-additives, respectively. Introduction of the co-additives led to a uniform surface morphology of photoactive layer and formed well distributed interpenetrating networks between donors and acceptors. Carrier recombination were reduced due to the favorable structure for charge transport. Consequently, the devices with co-additives achieved an enhanced performance with a PCE of 8.5% (JSC = 16.4 mA/cm2 and FF = 68.3%) in the fullerene system, and a PCE of 10.1% (JSC = 16.9 mA/cm2 and FF = 67.8%) in the non-fullerene system. In addition, the devices with co-additives showed improved stabilities compared to those with single additives. Correspondingly, the reduction ratio of PCE at ambient atmosphere conditions decreased from 17.07% to 10.59% in the fullerene system, and 34.02% to 24.75% in the non-fullerene system.