Optimizing Ferroelectric Photovoltaic Performance of KBNNO Ceramics via Grain Size Engineering for next generation solar cell

This study elucidates the pivotal role of grain size engineering in enhancing the ferroelectric photovoltaic (FPV) performance of 0.9[KNbO₃] - 0.1[BaNi_1/2Nb_1/2O_3-δ] [KBNNO] ceramics. A series of samples with grain sizes varying from 10 nm to 200 nm was synthesized via tailored sintering conditions. The grain growth significantly enhances ferroelectric polarization (from 12.45 to 26.50 µC/cm²) and increases the dielectric constant (from 1876 to ~3974 at 1 Hz) while maintaining the band gap in the visible region of the solar spectrum. Concurrently, the reduction in grain boundary density suppresses charge carrier recombination and strengthens conductive pathways, as evidenced by the increase in AC conductivity (from 132 to 660 µS/cm). These improvements directly contribute to superior photovoltaic performance, with photocurrent density increasing from 26 µA/cm² to 60 µA/cm², the highest value obtained, which is more than twice the previously reported value. Collectively, grain growth is a vital design parameter for optimizing FPV performance and providing a comprehensive multiscale framework linking microstructural and functional properties in electroceramics.

Keywords: Grain Size Engineering, Ferroelectric Photovoltaics (FPV), KBNNO, Microstructure Tuning, Electroceramics