Oxysalt based synergistic dual interfacial engineering for high performance p-i-n structured perovskite solar cells

Inverted perovskite solar cells (IPeSCs) have attracted extensive attention due to low-temperature processability and prospects for scale-up production. However, the power conversion efficiency (PCE) of IPeSCs lags compared to normal architecture, which is mainly due to inadequate interfaces of charge transport layers, viz electron and hole transport layers (ETL and HTL) and perovskite that suffers from carrier recombination paving the way for bulk recombination impeding the PCE and long-term stability of small devices. It is crucial to introduce an effective technique to reduce the interfacial non-radiative recombination losses at both interfaces of the perovskite layer. In this work, we demonstrated a multifunctional strategy to passivate the interface defects via the interactions and synergistic effect of anions and cations produced from sodium nitrate (NaNO₃), a π-conjugated oxysalt, at HTL/perovskite and ETL/perovskite interfaces. The synergistic effect of cation and anion bonding and interaction was confirmed by various experimental studies that decreased defect densities and improved the transfer of charges. The synergistic effect with double-side passivated devices showed a champion PCE of 21.53% as compared to pristine (19.08%), bottom (20.16%), and top (20.83%) passivated devices. The π-conjugated oxysalt also improved the IPeSC stability by building a moisture-resistant interface. This work signifies the effect of chemical bonding engineering via cations and anions at dual-perovskite interfaces for synergistically enhanced PCE and long-term stability of IPeSCs.