Structural and Optical Properties of Cs2AgBiBr6 Double Perovskite

ACS ENERGY LETTERS 4 (2019) 299-305

L Schade, AD Wright, RD Johnson, M Dollmann, B Wenger, PK Nayak, D Prabhakaran, LM Herz, R Nicholas, HJ Snaith, PG Radaelli

Solubilization of Carbon Nanotubes with Ethylene-Vinyl Acetate for Solution-Processed Conductive Films and Charge Extraction Layers in Perovskite Solar Cells.

ACS applied materials & interfaces 11 (2019) 1185-1191

G Mazzotta, M Dollmann, SN Habisreutinger, MG Christoforo, Z Wang, HJ Snaith, MK Riede, RJ Nicholas

Carbon nanotube (CNT) solubilization via non-covalent wrapping of conjugated semiconducting polymers is a common technique used to produce stable dispersions for depositing CNTs from solution. Here, we report the use of a non-conjugated insulating polymer, ethylene vinyl acetate (EVA), to disperse multi- and single-walled CNTs (MWCNT and SWCNT) in organic solvents. We demonstrate that despite the insulating nature of the EVA, we can produce semitransparent films with conductivities of up to 34 S/cm. We show, using photoluminescence spectroscopy, that the EVA strongly binds to individual CNTs, thus making them soluble, preventing aggregation, and facilitating the deposition of high-quality films. To prove the good electronic properties of this composite, we have fabricated perovskite solar cells using EVA/SWCNTs and EVA/MWCNTs as selective hole contact, obtaining power conversion efficiencies of up to 17.1%, demonstrating that the insulating polymer does not prevent the charge transfer from the active material to the CNTs.

Multi-band magnetotransport in exfoliated thin films of Cu x Bi2Se3.

Journal of physics. Condensed matter : an Institute of Physics journal 30 (2018) 155302-

JA Alexander-Webber, J Huang, J Beilsten-Edmands, P Čermák, Č Drašar, RJ Nicholas, AI Coldea

We report magnetotransport studies in thin (<100 nm) exfoliated films of Cu x Bi2Se3 and we detect an unusual electronic transition at low temperatures. Bulk crystals show weak superconductivity with [Formula: see text] K and a possible electronic phase transition around 200 K. Following exfoliation, superconductivity is supressed and a strongly temperature dependent multi-band conductivity is observed for T  <  30 K. This transition between competing conducting channels may be enhanced due to the presence of electronic ordering, and could be affected by the presence of an effective internal stress due to Cu intercalation. By fitting to the weak antilocalisation conductivity correction at low magnetic fields we confirm that the low temperature regime maintains a quantum phase coherence length [Formula: see text] nm indicating the presence of topologically protected surface states.

Multi-band magnetotransport in exfoliated thin films of Cu x Bi2Se3

Journal of Physics: Condensed Matter IOP Publishing 30 (2018) 155302-155302

JA Alexander-Webber, J Huang, J Beilsten-Edmands, P Čermák, Č Drašar, RJ Nicholas, AI Coldea

Modification of the fluorinated tin oxide/electron-transporting material interface by a strong reductant and its effect on perovskite solar cell efficiency


F Pulvirenti, B Wegner, NK Noel, G Mazzotta, R Hill, JB Patel, LM Herz, MB Johnston, MK Riede, HJ Snaith, N Koch, S Barlow, SR Marder

Carbon Nanotubes for Quantum Dot Photovoltaics with Enhanced Light Management and Charge Transport

ACS PHOTONICS 5 (2018) 4854-4863

Y Tazawa, SN Habisreutinger, N Zhang, DAF Gregory, G Nagamine, SV Kesava, G Mazzotta, HE Assender, M Riede, LA Padilha, RJ Nicholas, AAR Watt

Highly Crystalline Methylammonium Lead Tribromide Perovskite Films for Efficient Photovoltaic Devices

ACS ENERGY LETTERS 3 (2018) 1233-1240

NK Noel, B Wenger, SN Habisreutinger, JB Patel, T Crothers, Z Wang, RJ Nicholas, MB Johnston, LM Herz, HJ Snaith

Carbon Nanotubes in Perovskite Solar Cells


SN Habisreutinger, RJ Nicholas, HJ Snaith

Impact of microstructure on the electron-hole interaction in lead halide perovskites


AM Soufiani, Z Yang, T Young, A Miyata, A Surrente, A Pascoe, K Galkowski, M Abdi-Jalebi, R Brenes, J Urban, N Zhang, V Bulovic, O Portugall, Y-B Cheng, RJ Nicholas, A Ho-Baillie, MA Green, P Plochocka, SD Stranks

Ultrahigh magnetic field spectroscopy reveals the band structure of the three-dimensional topological insulator Bi2Se3

PHYSICAL REVIEW B 96 (2017) ARTN 121111

A Miyata, Z Yang, A Surrente, O Drachenko, DK Maude, O Portugall, LB Duffy, T Hesjedal, P Plochocka, RJ Nicholas

Investigating the Role of 4-Tert Butylpyridine in Perovskite Solar Cells


SN Habisreutinger, NK Noel, HJ Snaith, RJ Nicholas

Two-Dimensional Excitonic Photoluminescence in Graphene on a Cu Surface.

ACS nano 11 (2017) 3207-3212

Y Park, Y Kim, CW Myung, RA Taylor, CCS Chan, BPL Reid, TJ Puchtler, RJ Nicholas, LT Singh, G Lee, C-C Hwang, C-Y Park, KS Kim

Despite having outstanding electrical properties, graphene is unsuitable for optical devices because of its zero band gap. Here, we report two-dimensional excitonic photoluminescence (PL) from graphene grown on a Cu(111) surface, which shows an unexpected and remarkably sharp strong emission near 3.16 eV (full width at half-maximum ≤3 meV) and multiple emissions around 3.18 eV. As temperature increases, these emissions blue shift, displaying the characteristic negative thermal coefficient of graphene. The observed PL originates from the significantly suppressed dispersion of excited electrons in graphene caused by hybridization of graphene π and Cu d orbitals of the first and second Cu layers at a shifted saddle point 0.525(M+K) of the Brillouin zone. This finding provides a pathway to engineering optoelectronic graphene devices, while maintaining the outstanding electrical properties of graphene.

Impact of the Halide Cage on the Electronic Properties of Fully Inorganic Cesium Lead Halide Perovskites

ACS ENERGY LETTERS 2 (2017) 1621-1627

Z Yang, A Surrente, K Galkowski, A Miyata, O Portugall, RJ Sutton, AA Haghighirad, HJ Snaith, DK Maude, P Plochocka, RJ Nicholas

Unraveling the Exciton Binding Energy and the Dielectric Constant in Single-Crystal Methylammonium Lead Triiodide Perovskite.

The journal of physical chemistry letters 8 (2017) 1851-1855

Z Yang, A Surrente, K Galkowski, N Bruyant, DK Maude, AA Haghighirad, HJ Snaith, P Plochocka, RJ Nicholas

We have accurately determined the exciton binding energy and reduced mass of single crystals of methylammonium lead triiodide using magneto-reflectivity at very high magnetic fields. The single crystal has excellent optical properties with a narrow line width of ∼3 meV for the excitonic transitions and a 2s transition that is clearly visible even at zero magnetic field. The exciton binding energy of 16 ± 2 meV in the low-temperature orthorhombic phase is almost identical to the value found in polycrystalline samples, crucially ruling out any possibility that the exciton binding energy depends on the grain size. In the room-temperature tetragonal phase, an upper limit for the exciton binding energy of 12 ± 4 meV is estimated from the evolution of 1s-2s splitting at high magnetic field.

Spatially resolved studies of the phases and morphology of methylammonium and formamidinium lead tri-halide perovskites.

Nanoscale 9 (2017) 3222-3230

K Galkowski, AA Mitioglu, A Surrente, Z Yang, DK Maude, P Kossacki, GE Eperon, JT-W Wang, HJ Snaith, P Plochocka, RJ Nicholas

The family of organic-inorganic tri-halide perovskites including MA (MethylAmmonium)PbI3, MAPbI3-xClx, FA (FormAmidinium)PbI3 and FAPbBr3 are having a tremendous impact on the field of photovoltaic cells due to the combination of their ease of deposition and high energy conversion efficiencies. Device performance, however, is known to be still significantly affected by the presence of inhomogeneities. Here we report on a study of temperature dependent micro-photoluminescence which shows a strong spatial inhomogeneity related to the presence of microcrystalline grains, which can be both bright and dark. In all of the tri-iodide based materials there is evidence that the tetragonal to orthorhombic phase transition observed around 160 K does not occur uniformly across the sample with domain formation related to the underlying microcrystallite grains, some of which remain in the high temperature, tetragonal, phase even at very low temperatures. At low temperature the tetragonal domains can be significantly influenced by local defects in the layers or the introduction of residual levels of chlorine in mixed halide layers or dopant atoms such as aluminium. We see that improvements in room temperature energy conversion efficiency appear to be directly related to reductions in the proportions of the layer which remain in the tetragonal phase at low temperature. In FAPbBr3 a more macroscopic domain structure is observed with large numbers of grains forming phase correlated regions.

Dopant-Free Planar n-i-p Perovskite Solar Cells with Steady-State Efficiencies Exceeding 18%

ACS ENERGY LETTERS 2 (2017) 622-628

SN Habisreutinger, B Wenger, HJ Snaith, RJ Nicholas

A low viscosity, low boiling point, clean solvent system for the rapid crystallisation of highly specular perovskite films


NK Noel, SN Habisreutinger, B Wenger, MT Klug, MT Horantner, MB Johnston, RJ Nicholas, DT Moore, HJ Snaith

In-situ observation of stacking fault evolution in vacuum-deposited C-60


JFM Hardigree, IR Ramirez, G Mazzotta, C Nicklin, M Riede

Quantum dot-like excitonic behavior in individual single walled-carbon nanotubes.

Scientific reports 6 (2016) 37167-

X Wang, JA Alexander-Webber, W Jia, BPL Reid, SD Stranks, MJ Holmes, CCS Chan, C Deng, RJ Nicholas, RA Taylor

Semiconducting single-walled carbon nanotubes are one-dimensional materials with great prospects for applications such as optoelectronic and quantum information devices. Yet, their optical performance is hindered by low fluorescent yield. Highly mobile excitons interacting with quenching sites are attributed to be one of the main non-radiative decay mechanisms that shortens the exciton lifetime. In this paper we report on time-integrated photoluminescence measurements on individual polymer wrapped semiconducting carbon nanotubes. An ultra narrow linewidth we observed demonstrates intrinsic exciton dynamics. Furthermore, we identify a state filling effect in individual carbon nanotubes at cryogenic temperatures as previously observed in quantum dots. We propose that each of the CNTs is segmented into a chain of zero-dimensional states confined by a varying local potential along the CNT, determined by local environmental factors such as the amount of polymer wrapping. Spectral diffusion is also observed, which is consistent with the tunneling of excitons between these confined states.

The Impact of Phase Retention on the Structural and Optoelectronic Properties of Metal Halide Perovskites

Advanced Materials Wiley: 12 months (2016)

RJ Nicholas