Passivation of interstitial and vacancy mediated trap-states in triple-cation perovskite solar cells
Published at Journal of Power Sources [Elsevier]
Ultraviolet ozone (UVO) treatment reduces interstitial and vacancy mediated traps of ZnO film.
UVO treated ZnO ETL based perovskite solar cell (PSC) demonstrates 16.73% efficiency.
Perovskite film on UVO treated ZnO exhibits higher inter-particle connectivity and large grain.
UVO treatment reduces microstrain and dislocation density values of PSCs.
UVO treated ZnO based PSC retains 88% of its initial efficiency even after a month.
The work reports the concurrent passivation of interstitial and oxygen vacancy mediated defect states in low temperature processed ZnO electron transport layer (ETL) via Ultraviolet-Ozone (UVO) treatment for fabricating highly efficient (maximum efficiency: 16.70%), triple cation based MA0.57FA0.38Rb0.05PbI3 (MA: methyl ammonium, FA: formamidinium, Rb: rubidium) perovskite solar cell (PSC). Under UV exposure, ozone decomposes to free atomic oxygen and intercalates into the interstitial and oxygen vacancy induced defect sites in the ZnO lattice matrix, which contributes to suppressed trap-assisted recombination phenomena in perovskite device. UVO treatment also reduces the content of functional hydroxyl group on ZnO surface, that increases the inter-particle connectivity and grain size of perovskite film on UVO treated ZnO ETL. Owing to this, the perovskite film atop UVO treated ZnO film exhibits reduced micro-strain and dislocation density values, which contribute to the enhanced photovoltaic performance of PSC with modified ZnO ETL. The modified PSCs exhibit higher recombination resistance (RRec) ∼40% compared to pristine ZnO ETL based control devices. Adding to the merit, the UVO treated ZnO PSC also demonstrates superior device stability, retaining about 88% of its initial PCE in the course of a month-long, systematic degradation study.