Upscaling of perovskite solar cells to module scale and affording long-term stability have been recognized as the most important challenges for commercialization of this emerging photovoltaic technology. In a perovskite solar module (PSM), each interface within the device contributes to the efficiency and stability. Here, we employ a holistic interface stabilization strategy by modifying all the relevant layers and interfaces, namely the perovskite layer, charge transporting layers and the device encapsulation to improve the efficiency and stability of PSMs. The treatments were selected to be compatible with low-temperature scalable processing and the module scribing steps. Our unencapsulated PSM achieved a reverse-scan efficiency of 16.6% with a designated area of 22.4 cm 2 . The encapsulated PSM retained approximately 86% 2 of the initial performance after continuous operation for 2000 h under AM 1.5G light illumination, with translates into a T 90 lifetime of 1570 h and an estimated T 80 lifetime of 2680 h.

Solution processability of nanocrystals coated with a stable monolayer of organic ligands (nanocrystal-ligands complexes) is the starting point for their applications, which is commonly measured by their solubility in media. A model described in the other report (10.1021/acs.nanolett.6b00737) reveals that instead of offering steric barrier between inorganic cores, it is the rotation/bending entropy of the C-C σ bonds within typical organic ligands that exponentially enhances solubility of the complexes in solution. Dramatic ligand chain-length effects on the solubility of CdSe-n-alkanoates complexes shall further reveal the power of the model. Subsequently, "entropic ligands" are introduced to maximize the intramolecular entropic effects, which increases solubility of various nanocrystals by 10(2)-10(6). Entropic ligands can further offer means to greatly improve performance of nanocrystals-based electronic and optoelectronic devices.

In the past decade, the efficiency of perovskite solar cells quickly increased from 3.8% to 25.2%. The quality of perovskite films plays vital role in device performance. The films fabricated by solution‐process are usually polycrystalline, with significantly higher defect density than that of single crystal. One kind of defect in the films is uncoordinated Pb2+, which is usually generated during thermal annealing process due to the volatile organic component. Another detrimental kind of defect is Pb0, which is often observed during the film fabrication process or solar cell operation. Because the open circuit voltage has a close relation with the defect density, it is thus desirable to passivate these two kinds of defects. Here, a molecule with multiple ligands is introduced, which not only passivates the uncoordinated Pb2+ defects, but also suppresses the formation of Pb0 defects. Meanwhile, such a treatment improves the energy level alignment between the valence band of perovskite and the highest occupied molecular orbital of spiro‐OMeTAD. As a result, the performance of perovskite solar cells significantly increases from 19.0% to 21.4%.

We study the Kitaev model in a [001] magnetic field employing the mean field theory in the Majorana fermion representation. The mean field Hamiltonian of the system has the Bogoliubov de-Gennes (BdG) form of a 2D superconductor. We discover a robust gapless regime in intermediate magnetic field for both gapless and gapped anti-ferromagnetic Kitaev model with Jx = Jy before the system is polarized in high magnetic field. A topological phase transition connecting two gapless phases with a nodal line phase takes place at a critical magnetic field hc 1 in this regime. While the nodal line phase at hc 1 disappears when the mirror symmetry Jx = Jy is broken, the nodal point gapless phase can exist at intermediate fields even without the mirror symmetry. We reveal that the phase evolution of the system in the magnetic field is driven by the competition between the magnetic field and the particle-hole asymmetry of the normal state of the BdG Hamiltonian, which results in the robust intermediate gapless phase for the anti-ferromagnetic case. For ferromagnetic case, there is no intermediate phase transition before polarization. The above phase diagrams are confirmed by dynamical mean field theory results. arXiv:1806.04184v2 [cond-mat.str-el] 3 Sep 2018