Modulated surface photovoltage (SPV) spectra have been correlated with the phase composition in layers of CH3NH3PbI3 (MAPbI3) prepared from MAI and PbCl2 and annealed at 100 °C. Depending on the annealing time, different compositions of MAPbI3, MAPbCl3, MACl, PbI2, and an un-identified phase were found. It has been demonstrated that evaporation of MAI and HI is crucial for the development of electronic states in MAPbI3 and that only the appearance and evolution of the phase PbI2 has an influence on electronic states in MAPbI3. With ongoing annealing, (i) a transition from p- to n-type doping was observed with the appearance of PbI2, (ii) shallow acceptor states were distinguished and disappeared in n-type doped MAPbI3, and (iii) a minimum of the SPV response related to deep defect states was found at the transition from p- to n-type doping. The results are discussed with respect to the further development of highly efficient and stable MAPbI3 absorbers for solar cells.
Modulated charge separation across (MO)/CH3NH3PbI3 and (MO)/PbI2/CH3NH3PbI3 (MO = TiO2, MoO3) interfaces was investigated by surface photovoltage (SPV) spectroscopy. Perovskite layers were deposited by solution‐based one‐step preparation and two‐step preparation methods. An unreacted PbI2 layer remained at the interface between the metal oxide and CH3NH3PbI3 for two‐step preparation. For the two‐step preparation on TiO2, the SPV signal related to absorption in CH3NH3PbI3 increased in comparison to the one‐step preparation due to electron transfer from CH3NH3PbI3 via PbI2 into TiO2 whereas the SPV signal related to defect transitions decreased. For the one‐step preparation on MoO3, holes photogenerated in CH3NH3PbI3 recombined with electrons in MoO3. In contrast, a hole transfer from CH3NH3PbI3 towards MoO3 was blocked by the PbI2 interlayer for the two‐step preparation on MoO3. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)
Medical examination gloves made of natural rubber (NR; powdered and nonpowdered) and synthetic nitrile rubber (NBR) were compared in terms of their environmental impact using life cycle assessments spanning material extraction, transportation to the glove production factory, the production process, and disposal by total incineration. ReCiPe Midpoint (H) V1.13/World Recipe H life cycle assessment method implemented using the SimaPro 9.0.0.48, was used.Single scores of each glove type and stage were determined by using weighting factors specifically obtained from a 2014 survey in Thailand. With current technologies, the overall environmental impact, or the total single score, of NR gloves was higher than of NBR gloves, because the glove production stage of NR gloves required more energy and sulfur use. In addition, the overall environmental impact of both types of gloves was found to be lower if powder coating was used rather than chlorination to reduce stickiness, and if glove production relied on natural gas for energy rather than coal. The single score approach revealed the hotspots for potential improvements for each glove type.
The hybrid perovskite methylammonium lead iodide (CH 3 NH 3 PbI 3 ) combines a band gap between 1.5 eV and 1.6 eV [1,2], a high absorption coefficient of α ~ 10 4 cm -1 at 600 nm [3] and ambipolar diffusion lengths of around 100 nm [4,5]. The combined properties allowed solar cell efficiency boosting from e.g. 3 % in 2009 [6] to over 15 % in 2013 [7,8] and 16.2 % [9] / 17.9 % [10] in 2014. Perovskite thin film preparation can be drawn back to four major techniques: 1 st a co-evaporation of organic and inorganic precursors [8], 2 nd spin coating from dissolved perovskite [11][12][13][14][15][16][17], 3 rd in a sequential deposition process [7,[18][19][20] and 4 th using spray deposition [21,22]. Individual advantages enabling high efficiency and cost-effective processing are still under debate. Discussed effects range from reliable control over morphology [7,19,20,23], influence on material properties [24,25] to the formation of passivated interfaces [26][27][28].The key reaction in the sequential deposition is the transformation reaction of an inorganic precursor layer such as PbI 2 to the final CH 3 NH 3 PbI 3 by dipping into an organic precursor solution containing CH 3 NH 3 I. Providing high surface to volume ratio, observed reaction kinetics are fast (tens of seconds) [7]. The underlying mechanism is believed to be an insertion reaction, accelerated by the layered PbI 2 crystal structure [7,18,29]. Recently a model of the intercalation process on a molecular level was proposed based on in-situ photoluminescence (PL) studies of the intercalation depending on precursor concentration (3 -15 mM), solvent polarity and size of the organic component [29]. The proposed model starts with transformation of the first PbI 2 layer to an incomplete PbI 4 2-network, while created interstices allow organic intercalation and consecutive conversion of underlying layers [29]. Intercalation kinetics matched the JohnsonMehl-Avrami-Kolmogorov (JMAK) model [29].The objective of this work was the investigation of the Abstract: Mass transport during transformation of PbI 2 infiltrated in nanoporous TiO 2 into CH 3 NH 3 PbI 3 has been investigated by Rutherford backscattering spectroscopy (RBS). Fast initial reaction kinetics were confirmed using optical ex-situ and in-situ measurements. Mapping with energy dispersive X-ray spectroscopy of the cross section of samples revealed a homogeneous PbI 2 infiltration in nanoporous TiO 2 before transformation but an accumulation of Pb and I at the surface after transformation, in accordance with a depletion of Pb and I in a near surface region. Quantitative depth profiles of Pb and I were obtained from RBS analysis. An instant degradation of CH 3 NH 3 PbI 3 to PbI 2 and volatiles upon ion radiation was found. The concentration profiles of Pb could be simulated with a one dimensional diffusion model taking into account an effective diffusion coefficient of Pb in the nanocomposite (about 1.5⋅10 -11 cm²/s) as well as a parameter considering frazzling at the surface due to formation of crystallites.
The preparation of disubstituted derivatives of [ B3Hs]-with halogen or pseudo-halogen is reported.[B,H6CI(NCBH3)]-, and [B3H6CI-(NCBH,CI)] -. N.m.r. parameters show that the ions are fluxional in solution, and B-' B coupling is poorly resolved. The thermal stabilities, and chemical and electrochemical behaviour of representative compounds are described. The molecular structures, illustrated by [ B3H6@I2] -and [ B3H6CI-(NCS)] -relate to that of [B3H8] -with trans substituents. Four molecules of [N(PPh3),] [B,H,Ct,] crystallise in space group P 2 , / c with a = 10.9552(14), b = 12.840(9), c = 24.236(5) A, and p = * The isotropic thermal parameter is defined as exp[ -8n2U(sin28)/ A*].
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