Preparation of Single-Phase Films of CH3NH3Pb(I1-xBrx)3 with Sharp Optical Band Edges.

Organometallic lead-halide perovskite-based solar cells now approach 18% efficiency. Introducing a mixture of bromide and iodide in the halide composition allows tuning of the optical bandgap. We prepare mixed bromide-iodide lead perovskite films CH3NH3Pb(I1-xBrx)3 (0 ≤ x ≤ 1) by spin-coating from solution and obtain films with monotonically varying bandgaps across the full composition range. Photothermal deflection spectroscopy, photoluminescence, and X-ray diffraction show that following suitable fabrication protocols these mixed lead-halide perovskite films form a single phase. The optical absorption edge of the pure triiodide and tribromide perovskites is sharp with Urbach energies of 15 and 23 meV, respectively, and reaches a maximum of 90 meV for CH3NH3PbI1.2Br1.8. We demonstrate a bromide-iodide lead perovskite film (CH3NH3PbI1.2Br1.8) with an optical bandgap of 1.94 eV, which is optimal for tandem cells of these materials with crystalline silicon devices.We acknowledge funding from the Engineering and Physical Sciences Research Council (EPSRC) and the Winton Programme (Cambridge) for the Physics of Sustainability. THT acknowledges funding from Cambridge Australia Scholarships and the Cambridge Commonwealth Trust. D.C. acknowledges support from St. John's College Cambridge and the Winton Programme (Cambridge) for the Physics of Sustainability.This is the final published version. It's also available at: http://pubs.acs.org/doi/abs/10.1021/jz501332v

Atmospheric Influence upon Crystallization and Electronic Disorder and Its Impact on the Photophysical Properties of Organic–Inorganic Perovskite Solar Cells

Recently, solution-processable organic–inorganic metal halide perovskites have come to the fore as a result of their high power-conversion efficiencies (PCE) in photovoltaics, exceeding 17%. To attain reproducibility in the performance, one of the critical factors is the processing conditions of the perovskite film, which directly influences the photophysical properties and hence the device performance. Here we study the effect of annealing parameters on the crystal structure of the perovskite films and correlate these changes with its photophysical properties. We find that the crystal formation is kinetically driven by the annealing atmosphere, time and temperature. Annealing in air produces an improved crystallinity and large grain domains as compared to nitrogen. Lower photoluminescence quantum efficiency (PLQE) and shorter photoluminescence (PL) lifetimes are observed for nitrogen annealed perovskite films as compared to the air-annealed counterparts. We note that the limiting nonradiative pathways (<i>i.e</i>., maximizing PLQE) is important for obtaining the highest device efficiency. This indicates a critical impact of the atmosphere upon crystallization and the ultimate device performance

Retinoic acid signaling modulation guides in vitro specification of human heart field-specific progenitor pools.

Acknowledgements: We would like to acknowledge Birgit Campbell, Christina Scherb, and Marco Crovella for their technical assistance, Gabrielle Lederer (Cytogenetic Department, TUM) for karyotyping, Dr. Rupert Öllinger (TUM, Germany) for sequencing, Dr. David Elliott for sharing the ES03 and ES03-NKX2.5eGFP cell lines, Drs. Ed Stanley and Andrew Elefanty (MCRI, Australia) for advice in construct design and gene targeting, and Dr. Sasha Mendjan for advice and discussion. This work was supported by the European Research Council (ERC) (grant 788381 to A.Mo. and grant 261053 to K-.L.L.), the Else-Kroener-Fresenius Stiftung (EKFS, to A.G.), the German Research Foundation (grant GO3220/1-1 to A.G.; Transregio Research Unit 152 to A.Mo. and K-.L.L.; Transregio Research Unit 267 to A.Mo., K-.L.L., and P.G.), the German Centre for Cardiovascular Research (DZHK) (grant FKZ 81Z0600601 to A.Mo. and K-.L.L.; grant 81X3600607 to J.K.), the Fondazione Umberto Veronesi (to G.S.).Funder: German Centre for Cardiovascular ReserachFunder: Else Kröner-Fresenius-Stiftung (Else Kroner-Fresenius Foundation); doi: https://doi.org/10.13039/501100003042Cardiogenesis relies on the precise spatiotemporal coordination of multiple progenitor populations. Understanding the specification and differentiation of these distinct progenitor pools during human embryonic development is crucial for advancing our knowledge of congenital cardiac malformations and designing new regenerative therapies. By combining genetic labelling, single-cell transcriptomics, and ex vivo human-mouse embryonic chimeras we uncovered that modulation of retinoic acid signaling instructs human pluripotent stem cells to form heart field-specific progenitors with distinct fate potentials. In addition to the classical first and second heart fields, we observed the appearance of juxta-cardiac field progenitors giving rise to both myocardial and epicardial cells. Applying these findings to stem-cell based disease modelling we identified specific transcriptional dysregulation in first and second heart field progenitors derived from stem cells of patients with hypoplastic left heart syndrome. This highlights the suitability of our in vitro differentiation platform for studying human cardiac development and disease