Manipulating Electron Density Distribution of Nicotinamide Derivatives Toward Defect Passivation In Perovskite Solar Cells

摘要

The design of additives mainly involves selection of functional groups withcoordination relationships with defects in perovskite materials. However, it isparticularly important to further adjust the geometrical configuration andelectronic structure of an additive. Here, the nicotinamide (NA) and itsderivative 6-Methylnicotinamide (CNA) with electron-donor functional groupsare comparatively analyzed to investigate the effect of molecular dipole andelectronic configuration on the defect passivation of perovskite absorbers andthe photovoltaic properties of perovskite solar cells (PSCs). Theoreticalcalculations demonstrate that the CNA molecule with its large moleculardipole combine with the undercoordinated Pb~(2+) ions in perovskite to form ahigher binding energy, which is beneficial to improve the formation energy ofPb-related defects. Experimental characterization confirms that the CNAmolecule significantly enhances the coordination effect between acylaminoand undercoordinated defective Pb~(2+) cations, which is conducive to obtainhigh-quality, low-defect density of state, large grain size, and smooth surfaceperovskite absorbers. Thanks to the electronic configuration and electroniccloud distribution of CAN molecules, the PSCs yield impressive efficiency ashigh as 24.33% with excellent environmental storage, heat, and lightstabilities. This research provides a research basis for designing additiveswith steric-charge-dependence to assist perovskite photovoltaics.