Photovoltaic performance of a perovskite solar cell is observed to decrease with increasing humidity, which might be attributed to the formation of hydrated intermediates leading to a decrease in extraction of photocarriers. However, direct evidence of the interplay between the perovskite layer and the photovoltaic performance under operating conditions (consecutive illumination) has not yet been reported. Herein, we investigated the degradation of perovskite solar cells under operating situations through in situ X-ray diffraction and in situ X-ray absorption spectroscopies, which revealed that lead hydroxide iodide (PbIOH), a new phase that has not previously been identified as the degradation product of perovskite solar cells, was formed as an end decomposition product inside the cell. The formation of PbIOH could break the interface inside and be the key reason behind the problem of reduced cell life. This work illustrates that in operando direct observation of the photo-and moisture-induced effects can provide needed insights toward realizing stable perovskite solar cells.
Experimental methods, characterization data and 1 H NMR and 13 C NMR spectra of monomers for all polymers are described below.Materials. Fluorene, 3-bromothiophene, 3-thiophenecarboxaldehyde and malononitrile were obtained from Aldrich Chemical Co. 9,9-Dihexylfluorene. 1 To a solution of 5.0 gm (30.1 mmol) of fluorene in THF (60 ml) at -78 o C was added dropwise, 25 ml (62.5 mmol) of n-butyllithium (2.5 M in hexane).The mixture was stirred at -78 o C for 1 h, and 11.5 gm (70 mmol) of 1-bromohexane in THF (15 ml) was added dropwise to the mixture. The solution was allowed to warm to room temperature and was stirred for overnight. The mixture was poured into water and extracted with ether (3 X 30 ml). The organic layer was washed with brine solution and dried over anhydrous MgSO 4 . The solvent was removed by reduced
[reaction: see text] The title compound (1) has been synthesized via sequential Pd-catalyzed amination reactions and investigated as an intrinsic fluoroionophore. The efficiency in the synthesis of 1 strongly depends on the order of couplings among the substrates. Compound 1 displays fluorescence quenching upon the binding of transition metal ions, where the binding-triggered conformational twisting and in turn the inhibition of internal charge transfer (ICT) play an important role.
A series of low band gap, highly soluble alternating conjugated copolymers, comprised of 11,11,12,12-tetrahexylindenofluorene and thiophene derivatives (P1-P4), were synthesized via Pd-catalyzed Suzuki coupling reaction with very good yields. Described here are the synthesis, thermal, optical, and electrochemical properties of these new copolymers as potential new active materials for electronic and optoelectronic device applications. P1 and P2 have electron donating non-psubstituents with ethylenedioxy and propylenedioxy bridging the 3,3 positions of the cyclopentadithiophene groups; whereas P3 and P4 have electron withdrawing psubstituents (carbonyl and pyrazine groups on P3 and P4, respectively). For the main absorptions in UV-vis spectrum, P1 and P2 displayed more red absorptions in comparison with P3 and P4. Nevertheless, much suppressed quantum yields are exhibited by P3 and P4. The behaviors of P3 can be attributed to the significant charge transfer interactions between the p-substituents and the conjugated polymer backbone that leads to a less allowed optical transition between the ground and the lowest excited state. For P4, the weak fluoresence might associate with energy transfer from indenofluorene to the low band gap thiophene-pyrazinethiophene-thiophene (T-PT-T) unit. In comparison with the corresponding polymers containing fluorene instead of indenofluorene, the use of indenofluorene exhibited mixed effects on the optical properties and improved solubility. V
A pentiptycene-derived p-phenylenediamine mimics a molecular double-rotor system that displays redox-dependent rotation rates for the amino rotors about the pentiptycene-amine C-N bond. The rotation is accelerated in the radical cation state but stopped in the di(radical cation) state. Electronic interplay of the two rotors is also discussed.
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