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Although the application of graphene-derived nanomaterials in the electron transport layer (ETL), hole transport layer (HTL), or top electrode of perovskite solar cells (PSCs) has been thoroughly studied, the effects of inserting such materials into the perovskite layer of PSCs is not well understood. In this study, pristine graphene nanofibers were introduced into the perovskite layer of PSCs for the first time. The quality of the electrospun graphene nanofibers was optimized by controlled centrifugation of graphene sheets in the precursor suspension. Under optimized conditions, the device power conversion efficiency increased from 17.51 % without graphene to 19.83 % with graphene nanofibers, representing a 13 % increase. The introduction of graphene nanofibers into the perovskite layer led to a dramatic increase in the grain size of the perovskite layer to over 2 μm, owing to improved nucleation and crystallization at the nanofiber interface, which led to much higher FF and Jsc values. The significant increases in Jsc and Voc are attributed to the improved charge-transport properties of the graphene nanofibers with superb charge conductivity introduced into the perovskite layer. The latter was independently verified by the measured electron transport time. The stability of the device was also improved. In summary, an effective approach has been developed to improve the performance of PSCs by using pure graphene nanofibers for the first time.

BACKGROUND There is a demand to develop nano-photocatalyst that has better performance than existing TiO2 nanoparticles, which are difficult to separate and reuse. RESULTS Both TiO2 and TiO2/ZnO composite nanofibers prepared using sol–gel assisted electrospinning provided higher photocatalytic oxidation (PCO) of NO than TiO2 nanoparticles of 100 nm. The nanopores formed between nano-crystallites of nanofibers were found to increase both adsorption and activity of the photocatalyst. The TiO2/ZnO composite nanofiber photocatalyst has a lower band-gap than TiO2 nanofibers, which favors photo-electron generation, because introduction of ZnO causes charge imbalance and formation of unsaturated chemical bonds on the surface, increasing the catalyst surface oxygen vacancy and generation of the oxidation radicals, thereby increasing PCO. The efficiency of PCO under irradiation containing a full spectrum of wavelengths was optimized by adding 0.10 wt% of Zn to the TiO2 photocatalyst, and this optimal amount of added dopant was in accord with X-ray photoelectron spectroscopy measurement. The activity of the nanofiber photocatalysts was improved by increasing the irradiation area and residence time; and optimized at a relative humidity of 50%. CONCLUSION The present study demonstrates that enhanced PCO of NO with photocatalyst nanofiber can be optimized under solar light irradiation. © 2014 Society of Chemical Industry

A high power conversion efficiency of 10.24% can be obtained in a dye-sensitized solar cell by incorporating multiwall carbon nanotubes inside a TiO2 nanorod photoanode. The multiwall carbon nanotubes in the nanorod can effectively collect and transport photogenerated electrons reducing the recombination as well as improving efficiency of the device.