Synergistic effect of solvent and solid additives on morphology optimization for high-performance organic solar cells

Controlling the photoactive layer morphology towards nanoscale bi-continuous donor/acceptor interpenetrating networks is a key issue to build high-performance organic solar cells (OSCs). Due to the distinct properties between donor and acceptor materials, casting an active layer from a single solvent solution usually results in either insufficient or excessive phase separation that reduces the device performance. In comparison to the fullerene acceptors with closed-cage structures, the currently dominant non-fullerene acceptors possess the similar anisotropic pi-pi interactions with p-type organic semiconductor donors, giving rise to the complexity of the morphology regulation. Herein, we employ 4,4 '-dimethoxyoctafluorobiphenyl (OFP) with strong crystallinity as a volatile solid additive to optimize the active layer morphology of OSCs. The synergistic effect of 1-chloronaphthalene (CN) and OFP as dual additives shows supreme capability on optimizing the morphology over the conventional additive of CN, which is in favor of improving charge transport and suppressing charge recombination for higher fill factors in various systems. In particular, the PTQ10:m-BTP-C6Ph-based device processed by the additive showed a remarkable power-conversion efficiency (PCE) of 17.74%, whereas the control device processed by CN additive yielded a relatively lower PCE of 16.45%.

Automated summary

Controlling the morphology of the photoactive layer in organic solar cells is crucial for improving device performance. The use of a volatile solid additive, OFP, along with 1-chloronaphthalene shows superior capability in optimizing morphology, resulting in higher power conversion efficiency.