posted on 2024-02-14, 08:33authored byM. Alevli, N. Gungor, P. Kavak, N. Sahin, A. Corcor, I. Topal, K. Esmer, E. Cakmakci, C. Deger, I. Yavuz
We
study the structural and electronic mechanisms of potassium
(K+) incorporation in the FAPbI3 perovskite
layer. The K+ ions in FAPbI3 perovskite solar
cells lead to higher power conversion efficiency (PCE), lower trap
density, and faster charge transfer. K+ eliminates the I–V hysteresis for 5% K-doped perovskite.
Moreover, the phase stability is reduced by K+ incorporation.
The enhancement in PCE and reduced stability are attributed to the
passivation of deep-level charge traps and increased carrier mobility
and lower phase change activation energy, respectively, and in all
cases, KFA antisite formation is revealed, by density functional
theory (DFT) calculations, to be the main source. KFA has
reduced the electron–phonon coupling of charge transport and
the activation energy barrier for the cubic-to-hexagonal phase transformation,
which accelerates phase degradation. Our key findings will enable
the future design and optimization of high-efficiency and stable mixed-perovskite
solar cells.