In addition to a good perovskite light absorbing layer, the hole and electron transport layers play a crucial role in achieving high-efficiency perovskite solar cells. Here, a simple, one-step, solution-based method is introduced for fabricating high quality indium-doped titanium oxide electron transport layers. It is shown that indium-doping improves both the conductivity of the transport layer and the band alignment at the ETL/perovskite interface compared to pure TiO 2 , boosting the fill-factor and voltage of perovskite cells. Using the optimized transport layers, a high steady-state efficiency of 17.9% for CH 3 NH 3 PbI 3 -based cells and 19.3% for Cs 0.05 (MA 0.17 FA 0.83 ) 0.95 Pb(I 0.83 Br 0.17 ) 3based cells is demonstrated, corresponding to absolute efficiency gains of 4.4% and 1.2% respectively compared to TiO 2 -based control cells. In addition, a steady-state efficiency of 16.6% for a semi-transparent cell is reported and it is used to achieve a four-terminal perovskite-silicon tandem cell with a steady-state efficiency of 24.5%.

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We propose a versatile yet practical transferring technique to fabricate a high performance and extremely stable silver nanowire (AgNW) transparent electrode on arbitrary substrates. Hydroxylated poly(ethylene glycol) terephthalate (PET) or poly(dimethylsiloxane) (PDMS) deposited with AgNWs was selectively decorated to lower its polar surface energy, so that the AgNWs were easily and efficiently transferred into an epoxy resin (EPR) as a freestanding film (AgNWs-EPR) or onto various substrates. The AgNWs-EPR capped with alkanethiolate monolayers exhibits high conductivity, low roughness, ultraflexibility, and strong corrosion resistance. Using the transferring process, AgNWs-EPR was successfully constructed on rough, adhesive, flimsy, or complex curved substrates, including PET, thin optically clear adhesive, papers, a beaker, convex spherical PDMS, and leaves. A flexible touch panel enabling multitouch and a curved transparent heater on a beaker were first fabricated by using the composite film. These demonstrations suggest that the proposed technique for AgNWs is a promising strategy toward the next generation of flexible/portable/wearable electronics.

In this work, the interface electronic properties of ZnO(0001)/CH3NH3PbI3 were investigated by both X-ray and ultraviolet photoelectron spectroscopy. The CH3NH3PbI3 thin films were grown on single crystalline ZnO(0001) substrate in situ by co-evaporation of PbI2 and CH3NH3I at room temperature with various thickness from 1.5 nm to 190 nm. It was found that the conduction band minimum of ZnO lies 0.3 eV below that of CH3NH3PbI3, while the valence band maximum of ZnO lies 2.1 eV below that of CH3NH3PbI3, implying that the electrons can be effectively transported from CH3NH3PbI3 to ZnO, and the holes can be blocked in the same time. A PbI2 rich layer was initially formed at the interface of ZnO(0001)/CH3NH3PbI3 during the growth. As a consequence, an interface barrier was built up which may prevent the electron transport at the interface.

The surface magnetic domain structure of uncapped epitaxial FeRh/MgO(001) thin films was imaged by in-situ scanning electron microscopy with polarization analysis (SEMPA) at various temperatures between 122 and 450 K. This temperature range covers the temperature-driven antiferromagnetic-to-ferromagnetic phase transition in the body of the films that was observed in-situ by means of the more depth-sensitive magneto-optical Kerr effect. The SEMPA images confirm that the interfacial ferromagnetism coexisting with the antiferromagnetic phase inside the film is an intrinsic property of the FeRh(001) surface. Furthermore, the SEMPA data display a reduction of the in-plane magnetization occuring well above the phase transition temperature which, thus, is not related to the volume expansion at the phase transition. This observation is interpreted as a spin reorientation of the surface magnetization for which we propose a possible mechanism based on temperature-dependent tetragonal distortion due to different thermal expansion coefficients of MgO and FeRh.