Simultaneous Transport Promotion and Recombination Suppression in Perovskite Solar Cells by Defect Passivation with Li-Doped Graphitic Carbon Nitride

Among diverse strategies of improving the power conversion efficiency of perovskite solar cells (PSCs), one of the most effective pathways is to simultaneously promote charge transport and suppress charge recombination. Graphite carbon nitride (CN) is a promising additive for blocking the charge recombination in PSCs by passivating the trap states, which, however, usually leads to terrible charge transport performance as a side effect. Herein, we propose that this trade-off issue can be smoothly solved by simply replacing the intrinsic CN with its Li-doped counterpart (CN-Li). Specifically, introducing the CN-Li into perovskite films results in larger grain size with greater crystallinity, which further benefits the reduction of intrinsic defects and the elongation of the fluorescence lifetime. At the device level, the CN-Li modification not only dramatically passivates the trap states and suppresses the charge recombination but also decreases the series resistance and hence boosts the charge transport. Consequently, the CN-Li-modified PSC reaches a champion power conversion efficiency of 18.86% with a prominent short-circuit current density of 24.16 mA cm(-2). This work provides new insights into the efficiency optimization strategy of PSCs by simultaneously promoting charge transport and suppressing charge recombination.