Formamidinium lead
trioiodide (FAPbI3) is a promising
perovskite for single-junction solar cells. However, FAPbI3is metastable at room temperature and can cause intrinsic quantum
confinement effects apparent through a series of above-bandgap absorption
peaks. Here, we explore three common solution-based film-fabrication
methods, neatN,N-dimethylformamide
(DMF)–dimethyl sulfoxide (DMSO) solvent, DMF-DMSO with methylammonium
chloride, and a sequential deposition approach. The latter two offer
enhanced nucleation and crystallization control and suppress such
quantum confinement effects. We show that elimination of these absorption
features yields increased power conversion efficiencies (PCEs) and
short-circuit currents, suggesting that quantum confinement hinders
charge extraction. A meta-analysis of literature reports, covering
244 articles and 825 photovoltaic devices incorporating FAPbI3films corroborates our findings, indicating that PCEs rarely
exceed a 20% threshold when such absorption features are present.
Accordingly, ensuring the absence of these absorption features should
be the first assessment when designing fabrication approaches for
high-efficiency FAPbI3solar cells.