Tailoring vertical phase distribution of quasi-two-dimensional perovskite films via surface modification of hole-transporting layer

Abstract

Vertical phase distribution plays an important role in the quasi-two-dimensional perovskite solar cells. So far, the driving force and how to tailor the vertical distribution of layer numbers have been not discussed. In this work, we report that the vertical distribution of layer numbers in the quasi-two-dimensional perovskite films deposited on a hole-transporting layer is different from that on glass substrate. The vertical distribution could be explained by the sedimentation equilibrium because of the colloidal feature of the perovskite precursors. Acid addition will change the precursors from colloid to solution that therefore changes the vertical distribution. A self-assembly layer is used to modify the acidic surface property of the hole-transporting layer that induces the appearance of desired vertical distribution for charge transport. The quasi-two-dimensional perovskite cells with the surface modification display a higher open-circuit voltage and a higher efficiency comparing to reference quasi-two-dimensional cells.

Understanding the Interplay of Binary Organic Spacer in Ruddlesden–Popper Perovskites toward Efficient and Stable Solar Cells

“…However, in contrast to the front excitation (Figure d), we observe several extra emission peaks at higher energy (ascribed to small‐ n phases) when excited from the back side (Figure e). Such a difference observed in PL spectra excited from the front and back side indicates that the small‐ n phases have a preference to situate at the bottom of the RPP film near the substrate while the large‐ n (close to ∞) phases are located the upper surface of the film, which is highly consistent with previous reports 13a,14b,15. This spatial phase distribution can create a cascade energy band diagram (Figure S7, Supporting Information), which energetically facilitates photo‐induced electron transfer from small‐ n to large‐ n phases and hole transfer in the opposite direction.…”

“…Grazing‐incidence wide‐angle X‐ray scattering measurements are carried out to further probe the crystal orientation of the RPP films. As displayed in Figure g, the 0% BA film exhibits sharp and discrete Bragg spots rather than Debye–Scherrer rings, indicative of the formation of highly oriented crystalline grains 1b,15. By contrast, the narrower and more focused Bragg spots in both 50 and 100% BA films strongly manifest that the incorporation of a BA spacer can further enhance the vertical orientation of crystal domains (Figure h,i), consistent with the strengthened alignment of crystalline grains as observed in the cross‐sectional SEM images (Figure a–c).…”

Engineering Multiphase Metal Halide Perovskites Thin Films for Stable and Efficient Solar Cells

“…Discerning FA (CH 5 N 2 , MW = 172) and EA (C 2 H 8 N, MW = 173) cations is difficult since they have similar molecular weights. However, it has been reported by previous works that bulky cations in 2D/3D perovskites are likely to accumulate at the buried interface . X‐ray photoelectron spectroscopy measurement shows an identical surface chemical composition of EA‐FACs and FACs film (Table S1, Supporting Information), which may indicate that EA falls to the buried interface.…”

Incorporation of Hydrogen Molybdenum Bronze in Solution‐Processed Interconnecting Layer for Efficient Nonfullerene Tandem Organic Solar Cells

“…That would decrease the device performance; (2) there might be interaction between the PEDOT:PSS and the nonfullerene active layer of PM6:IT‐4F. PEDOT:PSS is a complicated system with high acidity having a pH value of 1–2 and strong oxidation property . Hydrogen bond between the F atoms in active layer and hydrogen in the acidic PEDOT:PSS might induce unfavorable vertical phase segregation of the PEDOT:PSS for charge transport.…”