The rapid development of organic-inorganic lead halide perovskites has resulted in high efficiency photovoltaic devices. However the susceptibility of these devices to degradation under environmental stress has so far hindered commercial development, requiring for example expensive device encapsulation. Herein, we have investigated the stability of CH3NH3Pb(I1-xBrx)3 [x = 0..1] thin film and solar cells under controlled humidity, light, and oxygen conditions. We show that higher bromide ratios increases tolerance to moisture, with x = 1 thin films being stable to 120 hr of moisture stress. Under light and dry air, partial bromide (x < 1) subsitution does not enhance film stability significantly, with the corresponding solar cells degrading within two hours. In contrast CH3NH3PbBr3 films show excellent stability, with device stability being limited by the organic interlayer. For these x = 1 films we show charge carriers are quenched in the presence of oxygen and form superoxide; however in contrast to perovskites containing iodide, this superoxide does not degrade the crystal. Our observations show that iodide limits the oxygen and light stability of CH3NH3Pb(I1-xBrx)3 perovskites, but that CH3NH3PbBr3 provides an opportunity to develop inherently stable high voltage photovoltaic devices and 4-terminal tandem solar cells.

Electro-Optical Materialshalide perovskite materials now exceed 20% power conversion efficiency, [1] and much progress has been made using these materials in other applications such as light-emitting diodes (LEDs) [2] and photodetectors. [3] The combination of advantageous optoelectronic properties (high absorption coefficient and long charge carrier diffusion lengths under operating conditions) and solution-based syntheses has spurred the investigation of morphological control of such materials. Time-resolved optical spectroscopies provide established methodologies to probe excited state dynamics, and have been key tools in developing our understanding of excited state dynamics of organolead halide perovskite materials. [4] Recent advances in synthetic procedures have led to the controlled formation of low dimensionality perovskite structures in order to tune their physical properties. [5] Solar cells made from layered 2D perovskites show greater moisture stability compared to devices prepared from 3D perovskites, [6] and 2D/3D mixtures have been shown to be promising for stable solar cells that retain high efficiency. [7] 0D perovskite nanoparticles (NPs) have attracted much attention to modify the optoelectronic properties of perovskite materials through quantum confinement. [8] Photophysical studies have shown that the size and morphology of perovskite crystallites influence their excited state dynamics. Key properties such as the recombination rate constants and charge carrier mobility can vary with changes

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Readily accessible tartramide ligands have been demonstrated to promote copper‐catalysed N‐arylation under mild conditions. In addition, the coupling protocol employs cheap and readily available pre‐catalyst, ligand, and base (NaOH), and overcomes many current limitations often associated with Ullmann coupling: it can be run with low catalyst loadings, does not require the use of excess amine, operates at room temperature, is fully homogeneous, and displays improved tolerance to air and moisture. Detailed kinetic studies using reaction progress kinetic analysis (RPKA) methods have provided insight into the factors influencing the reaction rate in terms of impact of ligand structure, reactant/catalyst dependence and catalyst (in)stability. These kinetic insights have been used in a quality‐by‐design approach for further optimization of the reaction protocol. The reaction scope was extended to 22 examples, showing broad applicability for a wide range of substituted aryl iodides with both primary and secondary amines.