In this study the concentration quenching phenomenon is explored for seven organic singlet emitters (Rhodamine 6G, Pyridine 2, Lumogen F Red 305, Perylene, Coumarin 102, DCM and DCJTB) in an inert host of poly(methyl methacrylate) (PMMA). Combining fluorescence lifetime and quantum yield measurements on samples of different molecular separation allows a deep decay rate analysis to be performed yielding, for each fluorophore, a monomial power law that indicates the strength and type of interaction. The fluorophores studied exhibit interactions in between that of FRET-like dipole–dipole (R−6) and surface–surface (R−2) with many lying close to that expected for surface–dipole (R−3) interactions. With no observed dependence on molecular structure it is concluded that the concentration quenching rate in singlet emitters follows a power law as kCQ = aR−3.1±0.7 with aggregation expected to increase the magnitude of the observed power.

•We identify typical errors affecting monitoring of large sets of small PV systems.•Largest errors are introduced by modeled horizontal irradiance and array’s azimuth.•Errors on typical UK system’s performance ratio and tilted irradiance are both ∼6%.•Long term: errors on orientation affect PR prediction; irradiance errors average out.•Performance ratio in UK is higher (lower) in summer (winter) than Continental Europe.Sources of error in the performance of large ensembles of spatially distributed photovoltaic generators are investigated and reported. Errors are propagated to estimate uncertainty in modeled global tilted radiation and performance ratio (PR)(PR) for the typical UK generator.Uncertainties in generators’ azimuth and elevation lead to typical monthly errors of 4% and 1% on global tilted radiation and PRPR. Interpolation of global horizontal irradiance is affected by an average 5% monthly error and the conversion to the inclined plane leads to an estimated error from 7% to 8% on tilted radiation and PRPR. This prediction has been verified against a set of twenty pyranometers on the plane of the array deployed across the UK, which gauge a 6% monthly error. Mutual cancellations lower this value to 4% for annual periodicity. The estimated monthly error on interpolated global horizontal irradiance is half of the 10% error affecting widely-used Photovoltaic Geographical Information System (PVGIS), which experiences larger errors also on the inclined plane. The assessed uncertainties impact the net present value of the investment required for deploying a PV generator; such an impact has been quantified.The yearly PRPR for the typical UK microgenerator is 84%, a value 8% (6%) higher than recent studies in France (Belgium). In winter, the typical UK performance ratio drops to 75%, because of an increase in shading. Summer performance ratio remains greater than the yearly mean, possibly reflecting the relatively short intervals during which direct sunlight heats the PV modules and the windy conditions over the British Isles. The monthly/annual error affecting the typical individual generator virtually cancel out for the whole national ensemble.

•Ultrathin molybdenum oxide films have been deposited via ultrasonic spray coating.•An ammonium molybdate tetrahydrate precursor is used to deposit from solution.•Post deposition thermal annealing causes thermal decomposition to MoO3.•OPV’s fabricated via ultrasonic spray coating show strong dependence upon annealing.•PCE’s of 4.4% achieved upon annealing MoO3 precursor at 350 °C.Polymer bulk heterojunction solar cells have been constructed using a thin film molybdenum oxide (MoOx) hole extraction layer that was fabricated by thermally annealing an ammonium molybdate tetrahydrate precursor layer deposited in air by ultrasonic spray-coating. Onto this layer was spray cast a PCDTBT:PC71BM film that acted as the active light-harvesting and charge-transporting layer. We optimise the processing steps used to convert the spray-cast MoOx precursor and show that the temperature at which it is annealed is critical to achieving high device efficiency as it both facilitates the removal of trapped solvent as well as driving its chemical conversion to MoOx. We demonstrate that by optimising the spray-casting and annealing process, we are able to create solar cell devices having a peak power conversion efficiency of 4.4%.Graphical abstract

The error in making a mean field approximation when analysing space charge limited currents in organic light emitting diodes has been assessed. Using a Poole Frenkel-like, exp(γE), field dependent mobility, space charge limited currents have been simulated using zero field mobilities from 10−10 m2/V s to 10−4 m2/V s and field dependent parameter γ from 10−7 (m/V)0.5 to 10−2 (m/V)0.5. The simulated current–voltage data has been fitted using a mean field approximation to a modified Mott–Gurney equation and the deviation of zero field mobility and γ from the real values has been calculated. It was found that for a significant range of the simulations the error in both the zero field mobility and the γ factor was invariant, but systematically underestimated by 2% and 15% respectively. We conclude that the mean field approximation is a useful method with which to assess mobility using space charge limited currents in organic semiconductor devices, but the accuracy of such an analysis can be improved by accounting for the systematic error.

In this study the concentration quenching phenomenon is explored for seven organic singlet emitters (Rhodamine 6G, Pyridine 2, Lumogen F Red 305, Perylene, Coumarin 102, DCM and DCJTB) in an inert host of poly(methyl methacrylate) (PMMA). Combining fluorescence lifetime and quantum yield measurements on samples of different molecular separation allows a deep decay rate analysis to be performed yielding, for each fluorophore, a monomial power law that indicates the strength and type of interaction. The fluorophores studied exhibit interactions in between that of FRET-like dipole–dipole (R−6) and surface–surface (R−2) with many lying close to that expected for surface–dipole (R−3) interactions. With no observed dependence on molecular structure it is concluded that the concentration quenching rate in singlet emitters follows a power law as kCQ = aR−3.1±0.7 with aggregation expected to increase the magnitude of the observed power.