Abstract:
Wide-bandgap lead bromide perovskites such as FAPbBr 3 are promising candidates for tandem
solar cells and high-voltage optoelectronic applications, yet their performance is limited by
surface and bulk defects that induce severe nonradiative recombination and limit stability. In this
work, we present a defect passivation and crystallization control strategy by incorporating
poly(methyl methacrylate) (PMMA) into the antisolvent during FAPbBr 3 film fabrication.
PMMA treatment leads to improved film morphology with larger grains, reduced surface
roughness, and enhanced crystallinity. FTIR analysis reveals that the carbonyl groups in PMMA
coordinate with undercoordinated Pb 2+ ions, effectively passivating electronic trap states.
Photothermal deflection spectroscopy (PDS) shows reduced sub-bandgap absorption and lower
Urbach energy, indicating suppressed deep-level defects and reduced energetic disorder.
Enhanced photoluminescence intensity, prolonged carrier lifetimes, and decreased trap densities
further confirm suppressed nonradiative recombination. As a result, PMMA treatment increases
Voc by over 100 mV and improves power conversion efficiency by more than 1%, achieving a
Voc of up to 1.510 V with reduced hysteresis and improved ambient stability. These findings
demonstrate the effectiveness of polymer-assisted strategies for improving both efficiency and
stability of wide-bandgap perovskite solar cells, offering a pathway toward high-voltage and
tandem photovoltaic applications.
