Radiation induced solid-state polymerization of acetylenedicarboxylic acid was carried out at room temperature in open atmosphere and under vacuum conditions. The gray colored powder polymer obtained was insoluble in most common solvents but only partially soluble in DMSO and THF. The limiting conversion to polymer was about 5%. The polymer was characterized by IR, UV, DP-MS, DSC, TGA, and XRD. The mechanism of polymerization was elucidated from the available data. Polymerization followed a free radical mechanism. However, before the addition of monomer molecules to the growing chain, at least one of the carboxylic groups of the monomer breaks away as CO or CO 2 . The formation of side group cyclization takes place. At least one of the bonds in the side cyclic group is an etheric bond. The DSC, TGA, and XRD results showed that the polymer was partially crystalline and showed no melting up to 1200 C. The mechanism of polymerization and assigned chain structure was studied by the direct pyrolysis mass spectrometric method.The crystal structure of monomer and polymer was investigated by the XRD method. Both monomer and crystalline polymer were monoclinic with similar cell parameters. Thus, the polymerization follows a topotactic mechanism. The unpolymerized monomer retains its crystal Downloaded by [DUT Library] at 12:28 06 October 2014 structure and, therefore, CO or CO 2 in the monomer molecule has to be eliminated before polymerization could take place.
This contribution demonstrates the effects of mole ratio, concentration of perovskite components and fullerene derivatives used as electron transport layer (ETL) on the stability and performances of inverted perovskite solar cells (PSCs). C60, C70, PC61BM and PC71BM are selected as ETL materials. Methylammonium iodide (MAI):Lead (II) iodide (PbI 2 ):Lead(II) chloride (PbCl 2 ) are used to form MAPb 2 I 2 Cl which is a mixed halogen perovskite structure. The fabricated perovskite device containing PCBM with optimized concentration and mole ratio gives high power conversion efficiency (PCE) of 9.07% with an open-circuit voltage (Voc) of 0.91 V, short circuit current density of 14.1 mA/cm 2 , and fill factor of 0.71. The lifetime characteristics and the stability are found significantly dependent on the fullerene type. The devices containing PC61BM and PC71BM are able to maintain 50% and 30% of its initial performances, respectively, even after 1100 hours. Overall, the obtained results represent an important step understanding the impacts on the p-i-n type perovskite lifetimes.
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