CuBr2-induced charge screening on photoactive nanocolloidal polypyrrole:poly(styrene sulfonate) composite multilayer thin-film counter electrodes for high-efficiency dye-sensitized solar cells

摘要

Nanocolloidal polypyrrole (PPy):poly(styrene sulfonate) (PSS) particles were synthesized by chemical oxidative polymerization using 15 wt% of PSS. The highly processable polymer composite (PPy:PSS) was spin-coated at 4000 rpm on fluorine-doped tin oxide glass and subsequently employed as a counter electrode (CE) for dye-sensitized solar cells (DSCs). PPy:PSS multilayer (one, three, five) CEs were treated with CuBr2 salt, which enhances the efficiency of the DSCs. Optical studies reveal that a bulkier counterion hinders interchain interactions of PPy which on salt treatment shows a moderate redshift in absorption maxima. Salt-treated PPy:PSS films exhibit lower charge transfer resistance, higher surface roughness and better catalytic performance for the reduction of I-3(-), when compared with untreated films. The improved catalytic performance of salt-treated PPy:PSS multilayer films is attributed to charge screening and conformational change of PPy, along with the removal of excess PSS. Under standard AM 1.5 sunlight illumination, salt treatment is shown to boost the efficiency of multilayer PPy:PSS composite film-based DSCs, leading to enhanced power conversion efficiency of 6.18, 6.33 and 6.37% for one, three and five layers, respectively. These values are significantly higher (ca 50%) than those for corresponding devices without CuBr2 salt treatment (3.48, 2.90 and 2.01%, respectively). (c) 2016 Society of Chemical Industry