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Perovskite solar cells (PSC) with efficiencies > 20% have only been realized with highly expensive archetype organic hole transporting materials that can impede the large-scale deployment of PSC. Here we demonstrate PSCs achieving stabilized efficiencies of 20.3% with CuSCN as hole electron extraction layer. We developed a new method for the solution deposition of compact and highly conformal CuSCN layers that afford fast carrier extraction and collection. We also show that the notorious instability of CuSCN based PSCs is not associated with the CuSCN/perovskite interface but rather originates from the CuSCN/Au contact. By introducing a thin spacer layer between CuSCN and gold layers, the PSCs retained >95% of their initial efficiency after aging for 500 h under full-sun illumination at 60 °C, and >85% of their initial efficiency after aging at 85 °C for 1000 h. Importantly, under both continuous illumination and thermal stress, CuSCN based devices surpass the stability of spiro-OMeTAD based PSCs.One Sentence Summary: A record performance displayed by operationally stable perovskite solar cells employing all-inorganic charge extraction layers was realized after introducing a simple dynamic approach for the deposition of thin and conformal CuSCN layer onto perovskite layer and a thin spacer layer between CuSCN and gold layers, which will foster their large scale deployment.The prominence of organic-inorganic perovskite solar cells (PSC) can be credited to the unprecedented advancement in the power conversion efficiencies (PCEs), realized mostly by tailoring the formation and composition of the absorber layer (1,2). Certified PCEs >20% have been obtained while retaining the electron selective TiO 2 layer and by using either spiroOMeTAD [2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9′-spirobifluorene] or a polymerbased PTTA (poly-triarylamine) as the hole-transporting material (HTM) (2,3). However, the cost of these HTMs is prohibitively high for large-scale applications and the long-term operational and thermal instability seems to be associated with the archetype organic HTMs or their ingredients (4). One of the strategies to combat the issues of cost and instability could be the use of inexpensive inorganic hole extraction layers similar to the use of TiO 2 as an electron transporting material (5). However, obtaining stable PCEs >20% with PSCs using inorganic 2 HTMs, such as NiO, CuI, Cs 2 SnI 6 , and CuSCN when subjected to light soaking under realistic operational conditions, i.e., at maximum power point and 60°C has remained a challenge (6-9).The realization of efficiencies > 20% using PSCs with inorganic HTMs remains undoubtedly a key goal to foster the large-scale deployment of PSC. Among various inorganic hole transporting materials, CuSCN is an extremely cheap, abundant p-type semiconductor, that exhibits high hole mobility, a good thermal stability and a well-aligned work function (10). The CuSCN is intrinsically p-doped and transmits light across the entire visible and near infrared spect...

Using a novel layer-by-layer approach we have deposited metal−organic open frameworks (MOFs) based on benzenetricarboxylic acid ligands and Cu(II)-ions on a COOH-terminated organic surface. The deposited layers were characterized using a number of surface analysis techniques. XRD measurements show that the MOFs deposited using this method have the same bulk structure of HKUST-1.

Preventing the degradation of metal perovskite solar cells (PSCs) by humid air poses a substantial challenge for their future deployment. We introduce here a two-dimensional (2D) A2PbI4 perovskite layer using pentafluorophenylethylammonium (FEA) as a fluoroarene cation inserted between the 3D light-harvesting perovskite film and the hole-transporting material (HTM). The perfluorinated benzene moiety confers an ultrahydrophobic character to the spacer layer, protecting the perovskite light-harvesting material from ambient moisture while mitigating ionic diffusion in the device. Unsealed 3D/2D PSCs retain 90% of their efficiency during photovoltaic operation for 1000 hours in humid air under simulated sunlight. Remarkably, the 2D layer also enhances interfacial hole extraction, suppressing nonradiative carrier recombination and enabling a power conversion efficiency (PCE) >22%, the highest reported for 3D/2D architectures. Our new approach provides water- and heat-resistant operationally stable PSCs with a record-level PCE.

We review recent developments in the area of self-assembled monolayers (SAMs) and their applications. First, we discuss issues related to the structure, the phase transitions, the phase diagram, and the growth dynamics. We explain how the internal degrees of freedom and the multiple interactions involved can lead to a fairly rich phase behaviour even for systems which are commonly considered 'simple' model systems. Then we discuss selected problems for more complex SAM-based systems, including SAMs as substrates for growth, SAMs and molecular electronics, electrochemical applications, and 'switchable' SAMs, as well as the use of SAMs for biofunctionalized surfaces and lateral structuring.

Macromolecular crowding in biological media is an essential factor for cellular function. The interplay of intermolecular interactions at multiple time and length scales governs a fine-tuned system of reaction and transport processes, including particularly protein diffusion as a limiting or driving factor. Using quasielastic neutron backscattering, we probe the protein self-diffusion in crowded aqueous solutions of bovine serum albumin on nanosecond time and nanometer length scales employing the same protein as crowding agent. The measured diffusion coefficient DðφÞ strongly decreases with increasing protein volume fraction φ explored within 7% ≤ φ ≤ 30%. With an ellipsoidal protein model and an analytical framework involving colloid diffusion theory, we separate the rotational D r ðφÞ and translational D t ðφÞ contributions to DðφÞ. The resulting D t ðφÞ is described by short-time self-diffusion of effective spheres. Protein self-diffusion at biological volume fractions is found to be slowed down to 20% of the dilute limit solely due to hydrodynamic interactions. macromolecular crowding | quasi-elastic neutron scattering | globular proteins T he interior of biological cells is a medium with a macromolecular volume fraction of up to 40%. This crowding crucially affects reaction kinetics and equilibria in the cell (1, 2). Cellular function and structure thus cannot be understood without a systematic understanding of both phase behavior and transport processes in crowded media. Diffusion is the main transport process for systems at low Reynolds numbers, governing many dynamic processes in nature (3). From the perspective of a single tracer molecule, all other molecules act as obstacles. In vivo diffusion coefficients for globular proteins in living cells (4-7) are strongly decreased compared to the in vitro diffusion coefficient in dilute buffer solutions. Systematic measurements of the tracer diffusion of proteins dissolved in concentrated suspensions of crowding agents, i.e., other proteins or polymers, reveal a complex dependence of the slowing down on the combination of tracer molecule and crowding agent (8-10). Furthermore, macromolecular crowding is found to induce subdiffusive behavior in several cases (11,12), being suggested as a slower but more reliable diffusive search process inside the cell (13). This anomalous diffusion process has been found also in theory and simulations (12-15) suggesting a crossover from subdiffusive behavior at small times to diffusive behavior at larger times.Proteins are macromolecules generally with a nonspherical shape and a nonhomogeneous surface charge, showing specific interactions with ligands. Furthermore, proteins not only show global motions like translational and rotational diffusion but also internal and interdomain motions. Therefore, proteins pose a challenge to colloid theory (16,17). In a recent simulation study Ando and Skolnick (4) revealed that using an equivalent-sphere model for macromolecules is a reasonable approximation to describe diffusion. Moreover, ...

We have studied a series of samples of bovine serum albumin (BSA) solutions with protein concentration, c, ranging from 2 to 500 mg/mL and ionic strength, I, from 0 to 2 M by small-angle X-ray scattering (SAXS). The scattering intensity distribution was compared to simulations using an oblate ellipsoid form factor with radii of 17 x 42 x 42 A, combined with either a screened Coulomb, repulsive structure factor, SSC(q), or an attractive square-well structure factor, SSW(q). At pH = 7, BSA is negatively charged. At low ionic strength, I < 0.3 M, the total interaction exhibits a decrease of the repulsive interaction when compared to the salt-free solution, as the net surface charge is screened, and the data can be fitted by assuming an ellipsoid form factor and screened Coulomb interaction. At moderate ionic strength (0.3-0.5 M), the interaction is rather weak, and a hard-sphere structure factor has been used to simulate the data with a higher volume fraction. Upon further increase of the ionic strength (I >or= 1.0 M), the overall interaction potential was dominated by an additional attractive potential, and the data could be successfully fitted by an ellipsoid form factor and a square-well potential model. The fit parameters, well depth and well width, indicate that the attractive potential caused by a high salt concentration is weak and long-ranged. Although the long-range, attractive potential dominated the protein interaction, no gelation or precipitation was observed in any of the samples. This is explained by the increase of a short-range, repulsive interaction between protein molecules by forming a hydration layer with increasing salt concentration. The competition between long-range, attractive and short-range, repulsive interactions accounted for the stability of concentrated BSA solution at high ionic strength.

Interface energetics are of fundamental importance in organic and molecular electronics. By combining complementary experimental techniques and first-principles calculations, we resolve the complex interplay among several interfacial phenomena that collectively determine the electronic structure of the strong electron acceptor tetrafluoro-tetracyanoquinodimethane chemisorbed on copper. The combination of adsorption-induced geometric distortion of the molecules, metal-to-molecule charge transfer, and molecule-to-metal back transfer leads to a net increase of the metal work function.