ZnO nanostructures with different morphologies (nanowires, nanodisks, and nanostars) were synthesized hydrothermally. Gas sensing properties of the as-grown nanostructures were investigated under thermal and UV activation. The performance of the ZnO nanodisk gas sensor was found to be superior to that of other nanostructures (Sg ∼ 3700% to 300 ppm ethanol and response time and recovery time of 8 and 13 s). The enhancement in sensitivity is attributed to the surface polarities of the different structures on the nanoscale. Furthermore, the selectivity of the gas sensors can be achieved by controlling the UV intensity used to activate these sensors. The highest sensitivity value for ethanol, isopropanol, acetone, and toluene are recorded at the optimal UV intensity of 1.6, 2.4, 3.2, and 4 mW/cm2, respectively. Finally, the UV activation mechanism for metal oxide gas sensors is compared with the thermal activation process. The UV activation of analytes based on solution processed ZnO structures pave the way for better quality gas sensors.

Flexible, fullerene-free organic solar cells with an efficiency exceeding 2% were fabricated by a roll-coating process and compared with fullerene-based devices.

Recent developments in solution processable single junction polymer solar cells have led to a significant improvement in power conversion efficiencies from ∼5% to beyond 9%. While much of the initial efficiency improvements were driven through judicious design of donor polymers, it is the engineering of device architectures through the incorporation of inorganic nanostructures and better processing that has continued the efficiency gains. Inorganic nano-components such as carbon nanotubes, graphene and its derivatives, metal nanoparticles and metal oxides have played a central role in improving device performance and longevity beyond those achieved by conventional 3G polymer solar cells. The present work aims to summarise the diverse roles played by the nanosystems and features in state of the art next generation (4G) polymer solar cells. The challenges associated with the engineering of such devices for future deployment are also discussed.

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The solution to the all polymer solar cell that breaks the 10% efficiency barrier keeps getting closer, with ever more scrutiny on each component in the active device for better performance. Much effort has been expended on the hole transport layers and photo-active polymer blends in these solution deposited photovoltaic cells. In this study we examine the merits of incorporating solution deposited metal oxide and hybrid metal oxide/reduced graphene oxide (RGO) based electron transport layers (ETL) with a view to providing further improvements to the PV cell architecture. Low bandgap active layer blends of [3,4-b]thiophene/benzodithiophene (PTB7) and [6,6]-phenyl C70 butyric acid methyl fullerene (PC 70 BM) with efficiencies in excess of 7% are fabricated and the performance of four different ETL material systems based on TiO 2 , ZnO, TiO 2 /RGO, ZnO/RGO are compared to thermally evaporated optimised reference bathocuproine (BCP) PV devices. Hybrid metal oxide/RGO ETL incorporated solution processed devices show an improved device performance compared to metal oxide only devices, with the performance comparable to the thermally evaporated BCP with fill factors of 68% and short circuit currents reaching 15 mA/cm 2 . The enhanced performance of the RGO incorporated hybrid ETL points the way for novel transport layers for all solution processed devices. BodyGrowing concerns with regards to the diminishing supply of fossil fuels and the impact of such non-renewables on global warming has made solar energy generation an important area of research. Of the many types of solar-energy converting systems, organic photovoltaics have attracted significant interest due to their low cost, light weight and the printable nature on flexible substrates.