Leveraging compatible iridium(III) complexes to boost performance of green solvent-processed non-fullerene organic solar cells

Abstract

In organic solar cells (OSCs), the short exciton lifetime poses a significant limitation to exciton diffusion and dissociation. Extending exciton lifetime and suppressing recombination are crucial strategies for improving the OSC performance. Herein, an effective approach is proposed by introducing the phosphorescent emitter, tris(2-(4-(tert-butyl)phenyl)-5-fluoropyridine)Iridium(III), with long-lived triplet exciton lifetime in OSCs. This research reveals that the steric structure of fac-Ir(tBufppy)3 exhibits excellent compatibility with both the donor PM6 and acceptor BTP-eC9, maintaining efficiencies of over 90% even with a 30% third component loading. Moreover, a 10% addition of fac-Ir(tBufppy)3 mitigates excessive aggregation in the acceptor BTP-eC9, optimizing the active layer morphology and improving the fill factor. Transient absorption spectroscopy and transient photoluminescence measurements demonstrate that the introduction of fac-Ir(tBufppy)3 significantly extends exciton lifetimes and suppresses recombination, which increases the short-circuit current (JSC). Ultimately, employing the non-halogenated solvent o-xylene for processing, an impressive power conversion efficiency (PCE) of 18.54% is achieved in devices based on PM6:10%fac-Ir(tBufppy)3:BTP-eC9, surpassing the efficiency of binary PM6:BTP-eC9 devices (17.41%). This work provides a promising approach to further improve the PCEs in binary OSCs by introducing a phosphorescent iridium(III) complex as the third component.