The present results demonstrate that transparent conductive epitaxial ITO films with atomically flat and stepped surfaces are vital for the lateral growth of organic molecules, taking vanadyl phthalocyanine (VOPc) as an example. Laterally grown organic molecules on transparent conductive substrates are essential for an emerging molecular electronics technology. Further, an epitaxial layer of VOPc on ITO films would provide new information to clarify the mechanism of improved hole-injection performance in OLEDs.Experimental YSZ (111) substrate was annealed at 1350 C in air to obtain an atomically flat surface [24]. The substrate temperature was maintained at 900 C during the film growth. An ITO (In 2 O 3 doped with 10 wt.-% SnO 2 ) ceramic target was set at the center of a PLD chamber. A YSZ substrate was positioned opposite to the target. The distance between the substrate and the target was 30 mm. The background pressure of the PLD chamber was 2 10 ±6 Pa, while the oxygen pressure during the growth was fixed at 3.0 10 ±3 Pa. An ITO film was grown on the rotating substrate by focusing a KrF excimer laser beam (k = 248 nm, pulse duration 20 ns, repetition frequency 10 Hz, photon energy density~1 J cm ±2 per pulse) onto the rotating target. The growth rate was 2 nm min ±1. The ITO film used as a substrate for VOPc layer growth was placed in an ultrahigh-vacuum MBE vessel (Eiko EVA-1000) [25] and preheated at 300 C for 2 h in the vessel. The base pressure of the vessel was 1 10 ±7 Pa. The substrate temperature was kept at 150 C [26] during the VOPc layer growth, while K-cell temperature was set at 245 C. The growth rate of VOPc, monitored by a quartz oscillator, was~1 nm min ±1. The crystalline quality and orientation of VOPc and ITO were analyzed by high-resolution X-ray diffraction measurements (HR-XRD, ATX-G, Rigaku Co.). Out-of-plane XRD (separate scan of 2h and x in the horizontal plane), inplane XRD (separate scan of 2hv and u in the azimuthal plane), out-of-plane rocking curve (2h fixed x scan), and in-plane rocking curve (2hd fixed u scan) measurements were performed. Surface morphologies of the VOPc layers were observed by AFM (SPI-3800N, S.I.I.) at room temperature in air.

We describe a facile method for the formation of dynamic nanostructured surfaces based on the modification of porous anodic aluminum oxide with poly(N-isopropyl acrylamide) (PNIPAAm) via surface-initiated atom transfer radical polymerization. The dynamic structure of these surfaces was investigated by atomic force microscopy (AFM), which showed dramatic changes in the surface nanostructure above and below the aqueous lower critical solution temperature of PNIPAAm. These changes in surface structure are correlated with changes in the macroscopic wettability of the surfaces, which was probed by water contact angle measurements. Principal component analysis was used to develop a quantitative correlation between AFM image intensity histograms and macroscopic wettability. Such correlations and dynamic nanostructured surfaces may have a variety of uses.

in dramatically improved environmental and structural stability. [2,3] However, the exciton binding energy of layered phases in 2D perovskites could be as high as 300 meV although this value could be reduced with the increased thickness of inorganic layer, resulting in relatively inferior photovoltaic performance compared to 3D perovskite solar cells (PSCs). [13] Thus, it is urgent to develop more efficient organic spacers as well as device engineering to obtain both highly efficient and stable 2D PSCs for future industry application.Ruddlesden-Popper (RP) and Dion-Jacobson (DJ) structures are two main archetypes of layered 2D perovskites to date. [14][15][16][17][18][19] The general formula of a 2D RP and DJ perovskite is (L′) 2 A n−1 M n X 3n+1 and (L″)A n−1 M n X 3n+1 , where L′ and A are monovalent cations, L″ is a divalent organic cation, M is a divalent metal cation, X is a halide ion, and n is the number of corner-sharing [MX 6 ] 4− octahedral slabs. [5] Typically, a van der Waals gap exist in organic spacers between adjacent inorganic [MI 6 ] 4octahedron slabs in 2D RP perovskites. [1] 2D RP perovskites have been shown enhanced stability, while the weak interlayer interactions in 2D RP perovskites with obvious van der Waals gaps cannot sufficiently stabilize their layered structure. In contrast, charge transport and stability could be enhanced in 2D DJ perovskites, where the neighboring inorganic slabs were bridged by diammonium spacers, resulting in shortened interslab distance and eliminated van der Waals gap. [1] So far, the aliphatic diammonium spacers, such as 1,4-butanediamine (BDA) and 1,3-propanediamine (PDA), have been studied in 2D DJ perovskite devices with promising photovoltaic performance. [20][21][22] However, the electrically insulating aliphatic diammonium spacers could block efficient charge transport due to their low dielectric constant. [23] In comparison with the aliphatic spacers, the aromatic spacers typically exhibit a larger dielectric constant and better conductivity due to the delocalized π-electrons along the molecular backbone, which could weaken the dielectric confinement effect by reducing dielectric mismatch between corner-sharing inorganic slabs and adjacent organic spacer layer. [23][24][25] Recently, several aromatic diammonium cations such as pyridinium-based aromatic spacers (3AMP, 4AMP), phenyl-based aromatic spacer (PDMA) and thiophene-based aromatic spacer (ThDMA) have been developed as organic spacers in 2D DJ PSCs to enhance the device performance. [23,[26][27][28][29][30] These single aromatic ringbased bulky spacers used so far still cannot directly contribute 2D Dion-Jacobson (DJ) perovskites have become an emerging photovoltaic material with excellent structure and environmental stability due to their lacking van der Waals gaps relative to 2D Ruddlesden-Popper perovskites. Here, a fused-thiophene-based spacer, namely TTDMAI, is successfully developed for 2D DJ perovskite solar cells. It is found that the DJ perovskite using TTDMA spacer with extended π-conjuga...

2D perovskites, such as 2D Ruddlesden-Popper (RP) and 2D Dion-Jacobson (DJ) perovskites, have attracted much attention owning to their better structure and environmental stability compared with their 3D analogs. [12][13][14][15][16] However, the efficiencies of 2D PSCs are still much lower than that of state-of-theart 3D PSCs. One strategy to combine the advantages of the high stability of 2D perovskite and high efficiency of 3D perovskite is developing the 2D/3D hybrid perovskites by embedding a highly stable 2D perovskite into a 3D perovskite matrix. So far, the 2D/3D hybrid perovskites has shown great promise in high performance PSCs, which may promote the commercial application of this technology. [17][18][19][20][21] In 2017, Snaith et al. reported that the introducing of n-butylammonium (BA) cations into a mixed-cation 3D perovskite using a one-step deposition method achieved an average stabilized PCE of ≈17.5% with a 1.61-eV-bandgap perovskite. [19] In 2019, 2-thiophenemethylammonium (ThMA) was used as organic spacer to construct the 2D/3D perovskite. It was found that the ThMAI could assist the perovskite crystal growth and orientation, achieving a high efficiency of 21.49% with significantly improved film and device stability. [20] Huang et al. reported that incorporating 0.83 molar percent phenethylammonium chloride (PEACl) into perovskite inks enables highly crystalline formamidine (FA)-alloyed perovskites with extraordinary optoelectronic properties and achieving a high efficiency of 22.0%. [22] Due to the abundant and inevitable defects generated during film fabrication, the quality of the solution-processed perovskite films play a very important role for their photovoltaic properties and device stability. Although some excellent works have been done to improve the PCE and stability by developing different organic spacers, [19][20][21][22][23][24] the crystal nucleation and growth mechanism of 2D/3D perovskite is still not very clear and is largely unexplored. Moreover, the development of efficient crystal growth regulation strategies and understanding the crystallization kinetics in 2D/3D perovskite films are the path to high performance PSCs for future commercial application.In this work, we demonstrate the fabrication of high-quality 2D/3D hybrid perovskite by crystal growth regulation with 2D (NpMA) 2 PbI 4 perovskite. A 2D (NpMA) 2 PbI 4 perovskite and 1-naphthalenemethylammonium iodide (NpMAI) were introduced to the PbI 2 precursor respectively to modulate the crystal growth in 2D/3D perovskite film using a two-step deposition method. The cross-section scanning electron microscopy Reducing the electronic defects in perovskite films has become a substantial challenge to further boost the photovoltaic performance of perovskite solar cells. Here, 2D (NpMA) 2 PbI 4 perovskite and 1-naphthalenemethylammonium iodide (NpMAI) are separately introduced into the PbI 2 precursor solutions to regulate the crystal growth in a 2D/3D perovskite film using a two-step deposition method. The (NpMA) 2 PbI 4 modul...

Organic spacers play an important role in 2D/3D hybrid perovskites, which could combine the advantages of high stability of 2D perovskites and high efficiency of 3D perovskites. Here, a class of aromatic formamidiniums (ArFA) was developed as spacers for 2D/3D perovskites. It is found that the bulky aromatic spacer ArFA in 2D/3D perovskites could induce better crystalline growth and orientation, reduce the defect states, and enlarge spatially resolved carrier lifetime thanks to the multiple NH•••I hydrogen-bonding interactions between ArFA and inorganic [PbI 6 ] 4− layers. As a result, compared to the control device with efficiency of 19.02%, the 2D/3D perovskite device based on such an optimized organic salt, namely benzamidine hydrochloride (PhFACl), exhibits a dramatically improved efficiency of 22.39% along with improved long-term thermal stability under 80 °C over 1400 h. Importantly, a champion efficiency of 23.36% was further demonstrated through device engineering for PhFACl-based 2D/3D perovskite solar cells. These results indicate the great potential of this class of ArFA spacers in highly efficient 2D/3D perovskite solar cells.