Extended Data Fig. 7: Gap states in the YbOx film and charge-carrier transport measurements.
From: Multifunctional ytterbium oxide buffer for perovskite solar cells
a, Yb 4d XPS spectra of the YbOx film with a thickness of 40 nm. b, Valence band spectra of YbOx. There exists a considerable density of gap states below the Fermi level. c, Current density−voltage characteristics of the ITO/[YbOx (2 nm)]20/Cu over temperature ranged from 120 K to 300 K. Note that the 40 nm YbOx deposition is completed by evaporating 20 alternative layers. d, The plot of conductivity against temperature. The conductivity is calculated at 26 mA cm−2, where the injected current is equal to the short-circuit current of a narrow-bandgap PSC under 1-sun illumination. Note that the pre-factor σ0 = (2.22 ± 0.47) × 10−3 S m−1, and the characteristic parameter B = 10.33 ± 0.81.
