Inorganic organic interfaces in hybrid solar cells

In this review, we present important concepts to describe inorganic organic interfaces in hybrid solar cells. We discuss the formation of hybrid interfaces, provide an introduction to the ground state electronic structure of the individual components, and detail the overall electronic landscape after combining into a hybrid material for different relevant cases. We then explore the impact of hybrid interfaces on photophysical processes that are crucial for the photovoltaic performance of hybrid solar cells. Within this framework, we discuss methods for hybrid interface modification toward the optimization of hybrid solar cells, such as doping, the application of interlayers, and morphological contro

Interdependence of photon upconversion performance and antisolvent processing in thin film halide perovskite sensitized triplet triplet annihilators

We prepared triplet triplet annihilation photon upconverters combining thin film methylammonium lead iodide MAPI perovskite with a rubrene annihilator in a bilayer structure. Excitation of the perovskite film leads to delayed, upconverted photoluminescence emitted from the annihilator layer, with triplet excitation of the rubrene being driven by carriers excited in the perovskite layer. To better understand the connections between the semiconductor properties of the perovskite film and the upconversion efficiency, we deliberately varied the perovskite film properties by modifying two spin coating conditions, namely, the choice of antisolvent and the antisolvent dripping time, and then studied the resulting photon upconversion performance with a standard annihilator layer. A stronger upconversion effect was exhibited when the perovskite films displayed brighter and more uniform photoluminescence. Both properties were sensitive to the antisolvent dripping time and were maximized for a dripping time of 20 s measured relative to the end of the spin coating program . Surprisingly, the choice of antisolvent had a significant effect on the upconversion performance, with anisole treated films yielding on average a tenfold increase in upconversion intensity compared to the chlorobenzene treated equivalent. This performance difference was correlated with the carrier lifetime in the perovskite film, which was 52 ns and 306 ns in the brightest chlorobenzene and anisole treated films, respectively. Since the bulk properties of the anisole and chlorobenzene treated films were virtually identical, we concluded that differences in the defect density at the MAPI rubrene interface, linked to the choice of antisolvent, must be responsible for the differing upconversion performanc

A new geodemographic classification of commuting flows for England and Wales

This paper aims to contribute to the area of geodemographic research through the development of a new and novel flow-based classification of commuting for England and Wales. In doing so, it applies an approach to the analysis of commuting in which origin-destination flow-data, collected as part of the 2011 census of England and Wales, are segmented into groups based on shared similarities across multiple demographic and socioeconomic attributes. K-means clustering was applied to 49 flow-based commuter variables for 513,892 interactions that captured 18.4 million of the 26.5 million workers recorded as part of the 2011 census of England and Wales. The final classification resulted in an upper-tier of nine ‘Supergroups’ which were subsequently partitioned to derive a lower-tier of 40 ‘Groups’. A nomenclature was developed and associated pen-portraits derived to provide basic signposting to the dominant characteristics of each cluster. Analysis of a selection of patterns underlying the nine-fold Supergroup configuration revealed a highly variegated structure of commuting in England and Wales. The classification has potentially wide-ranging descriptive and analytical applications within research and policy domains and the approach would be equally transferable to other countries and contexts where origin-destination data is disaggregated based on commuter characteristics

Increased upconversion performance for thin film solar cells a trimolecular composition

Photochemical upconversion based on triplet triplet annihilation TTA UC is employed to enhance the short circuit currents generated by two varieties of thin amp; 64257;lm solar cells, a hydrogenated amorphous silicon a Si H solar cell and a dye sensitized solar cell DSC . TTA UC is exploited to harvest transmitted sub bandgap photons, combine their energies and re radiate upconverted photons back towards the solar cells. In the present study we employ a dual emitter TTA UC system which allows for signi amp; 64257;cantly improved UC quantum yields as compared to the previously used single emitter TTA systems. In doing so we achieve record photo current enhancement values for both the a Si H device and the DSC, surpassing 10 3 mA cm 2 sun 2 for the amp; 64257;rst time for a TTA UC system and marking a record for upconversion enhanced solar cells in general. We discuss pertinent challenges of the TTA UC technology which need to be addressed in order to achieve its viable device application

Crystalline silicon solar cells with tetracene interlayers the path to silicon singlet fission heterojunction devices

Singlet exciton fission is an exciton multiplication process that occurs in certain organic materials, converting the energy of single highly-energetic photons into pairs of triplet excitons. This could be used to boost the conversion efficiency of crystalline silicon solar cells by creating photocurrent from energy that is usually lost to thermalisation. An appealing method of implementing singlet fission with crystalline silicon is to incorporate singlet fission media directly into a crystalline silicon device. To this end, we developed a solar cell that pairs the electron-selective contact of a high-efficiency silicon heterojunction cell with an organic singlet fission material, tetracene, and a PEDOT:PSS hole extraction layer. Tetracene and n-type crystalline silicon meet in a direct organic-inorganic heterojunction. In this concept the tetracene layer selectively absorbs blue-green light, generating triplet pairs that can dissociate or resonantly transfer at the organo-silicon interface, while lower-energy light is transmitted to the silicon absorber. UV photoemission measurements of the organic-inorganic interface showed an energy level alignment conducive to selective hole extraction from silicon by the organic layer. This was borne out by current-voltage measurements of devices subsequently produced. In these devices, the silicon substrate remained well-passivated beneath the tetracene thin film. Light absorption in the tetracene layer created a net reduction in current for the solar cell, but optical modelling of the external quantum efficiency spectrum suggested a small photocurrent contribution from the layer. This is a promising first result for the direct heterojunction approach to singlet fission on crystalline silicon

Optical and Spin Properties of NV Center Ensembles in Diamond Nano Pillars

Nitrogen vacancy NV color centers in diamond are excellent quantum sensors possessing high sensitivity and nano scale spatial resolution. Their integration in photonic structures is often desired, since it leads to an increased photon emission and also allows the realization of solid state quantum technology architectures. Here, we report the fabrication of diamond nano pillars with diameters up to 1000 nm by electron beam lithography and inductively coupled plasma reactive ion etching in nitrogen rich diamonds type Ib with [100] and [111] crystal orientations. The NV centers were created by keV He ion bombardment and subsequent annealing, and we estimate an average number of NVs per pillar to be 4300 300 and 520 120 for the [100] and [111] samples, respectively. Lifetime measurements of the NVs excited state showed two time constants with average values of amp; 964;1 amp; 8776; 2 ns and amp; 964;2 amp; 8776; 8 ns, which are shorter as compared to a single color center in a bulk crystal amp; 964; amp; 8776; 10 ns . This is probably due to a coupling between the NVs as well as due to interaction with bombardment induced defects and substitutional nitrogen P1 centers . Optically detected magnetic resonance measurements revealed a contrast of about 5 and average coherence and relaxation times of T2 [100] 420 40 ns, T2 [111] 560 50 ns, and T1 [100] 162 11 amp; 956;s, T1 [111] 174 24 amp; 956;s. These pillars could find an application for scanning probe magnetic field imagin

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)= 7 TeV using 35 pb-1 of ATLAS data

A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<=|eta|<2.37 in the transverse energy range 45<=E_T<400GeV. The results are based on an integrated luminosity of 35 pb-1, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.Comment: 7 pages plus author list (18 pages total), 2 figures, 4 tables, final version published in Physics Letters