Publications


Non-polar nitride single-photon sources

Journal of Optics IOP Publishing 22 (2020) 073001-073001

T Wang, RA Oliver, RA Taylor


Purcell enhancement of a deterministically coupled quantum dot in an SU-8 laser patterned photonic crystal heterostructure

Applied Physics Letters AIP Publishing 117 (2020) 043103-043103

H Shao, G Ying, S Lennon, F Brossard, J Griffiths, L Nuttall, V Osokin, E Clarke, H He, R Taylor


Revealing Factors Influencing the Operational Stability of Perovskite Light-Emitting Diodes

ACS Nano American Chemical Society (ACS) (2020) acsnano.0c03516

JH Warby, B Wenger, AJ Ramadan, RDJ Oliver, HC Sansom, AR Marshall, HJ Snaith


Understanding the Performance-Limiting Factors of Cs2AgBiBr6 Double-Perovskite Solar Cells

ACS ENERGY LETTERS 5 (2020) 2200-2207

G Longo, S Mahesh, LRV Buizza, AD Wright, AJ Ramadan, M Abdi-Jalebi, PK Nayak, LM Herz, HJ Snaith


Three-dimensional cross-nanowire networks recover full terahertz state

Science American Association for the Advancement of Science 368 (2020) 510-513

K Peng, D Jevtics, F Zhang, S Sterzl, D Damry, M Rothmann, B Guilhabert, MJ Strain, HH Tan, LM Herz, L Fu, MD Dawson, A Hurtado, C Jagadish, M Johnston

Terahertz radiation encompasses a wide band of the electromagnetic spectrum, spanning from microwaves to infrared light, and is a particularly powerful tool for both fundamental scientific research and applications such as security screening, communications, quality control, and medical imaging. Considerable information can be conveyed by the full polarization state of terahertz light, yet to date, most time-domain terahertz detectors are sensitive to just one polarization component. Here we demonstrate a nanotechnology-based semiconductor detector using cross-nanowire networks that records the full polarization state of terahertz pulses. The monolithic device allows simultaneous measurements of the orthogonal components of the terahertz electric field vector without cross-talk. Furthermore, we demonstrate the capabilities of the detector for the study of metamaterials.


Quantification of Photophysical Processes in All-Polymer Bulk Heterojunction Solar Cells

SOLAR RRL 4 (2020) ARTN 2000181

AH Balawi, Z Kan, J Gorenflot, P Guarracino, N Chaturvedi, A Privitera, S Liu, Y Gao, L Franco, P Beaujuge, F Laquai


Coarse and fine-tuning of lasing transverse electromagnetic modes in coupled all-inorganic perovskite quantum dots

Nano Research Springer Science and Business Media LLC (2020)

Y Park, G Ying, A Jana, V Osokin, CC Kocher, T Farrow, RA Taylor, KS Kim

<jats:title>Abstract</jats:title> <jats:p>Inorganic perovskite lasers are of particular interest, with much recent work focusing on Fabry-Pérot cavity-forming nanowires. We demonstrate the direct observation of lasing from transverse electromagnetic (TEM) modes with a long coherence time ∼ 9.5 ps in coupled CsPbBr<jats:sub>3</jats:sub> quantum dots, which dispense with an external cavity resonator and show how the wavelength of the modes can be controlled via two independent tuning-mechanisms. Controlling the pump power allowed us to fine-tune the TEM mode structure to the emission wavelength, thus providing a degree of control over the properties of the lasing signal. The temperature-tuning provided an additional degree of control over the wavelength of the lasing peak, importantly, maintained a constant full width at half maximum (FWHM) over the entire tuning range without mode-hopping.</jats:p>


Publisher Correction: Deciphering photocarrier dynamics for tuneable high-performance perovskite-organic semiconductor heterojunction phototransistors.

Nature communications 11 (2020) 2956-

Y-H Lin, W Huang, P Pattanasattayavong, J Lim, R Li, N Sakai, J Panidi, MJ Hong, C Ma, N Wei, N Wehbe, Z Fei, M Heeney, JG Labram, TD Anthopoulos, HJ Snaith

An amendment to this paper has been published and can be accessed via a link at the top of the paper.


On the absence of triplet exciton loss pathways in non-fullerene acceptor based organic solar cells

MATERIALS HORIZONS 7 (2020) 1641-1649

MS Kotova, G Londi, J Junker, S Dietz, A Privitera, K Tvingstedt, D Beljonne, A Sperlich, V Dyakonov


Ultrafast Charge Dynamics in Dilute-Donor versus Highly Intermixed TAPC:C60 Organic Solar Cell Blends.

The journal of physical chemistry letters (2020)

GJ Moore, M Causa', JF Martinez Hardigree, S Karuthedath, IR Ramirez, A Jungbluth, F Laquai, MK Riede, N Banerji

Elucidating the interplay between film morphology, photophysics, and device performance of bulk heterojunction (BHJ) organic photovoltaics remains challenging. Here, we use the well-defined morphology of vapor-deposited di-[4-(N,N-di-p-tolyl-amino)-phenyl]cyclohexane (TAPC):C60 blends to address charge generation and recombination by transient ultrafast spectroscopy. We gain relevant new insights to the functioning of dilute-donor (5% TAPC) fullerene-based BHJs compared to molecularly intermixed systems (50% TAPC). First, we show that intermolecular charge transfer (CT) excitons in the C60 clusters of dilute BHJs rapidly localize to Frenkel excitons prior to dissociating at the donor:acceptor interface. Thus, both Frenkel and CT excitons generate photocurrent over the entire fullerene absorption range. Second, we selectively monitor interfacial and bulk C60 clusters via their electro-absorption, demonstrating an energetic gradient that assists free charge generation. Third, we identify a fast (< 1 ns) recombination channel, whereby free electrons recombine with trapped holes on isolated TAPC molecules. This can harm the performance of dilute solar cells, unless the electrons are rapidly extracted in efficient devices.


Postpassivation of Multication Perovskite with Rubidium Butyrate

ACS Photonics American Chemical Society (ACS) (2020) acsphotonics.0c00878

JC Germino, R Szostak, SG Motti, RF Moral, PE Marchezi, HS Seleghini, LG Bonato, FL de Araújo, TDZ Atvars, LM Herz, D Fenning, A Hagfeldt, AF Nogueira


A phosphine oxide route to formamidinium lead tribromide nanoparticles

Chemistry of Materials American Chemical Society (ACS) (2020) acs.chemmater.0c00590

OJ Ashton, AR Marshall, JH Warby, B Wenger, HJ Snaith


Simple technique for determining the refractive index of phase-change materials using near-infrared reflectometry

Optical Materials Express The Optical Society 10 (2020) 1675-1675

E Gemo, S Kesava, C Ruiz De Galarreta, L Trimby, S García-Cuevas Carrillo, M Riede, A Baldycheva, A Alexeev, C Wright


Preventing phase segregation in mixed-halide perovskites: a perspective

Energy & Environmental Science Royal Society of Chemistry (RSC) (2020)

AJ Knight, LM Herz

&lt;p&gt;Halide segregation represents a severe stability problem for certain mixed-halide perovskites. Here we explore a myriad of methods for mitigating halide segregation, including several largely unexplored approaches that show significant promise.&lt;/p&gt;


A piperidinium salt stabilizes efficient metal-halide perovskite solar cells.

Science (New York, N.Y.) Nature Research 369 (2020) 96-102

Y-H Lin, N Sakai, P Da, J Wu, HC Sansom, AJ Ramadan, S Mahesh, J Liu, RDJ Oliver, J Lim, L Aspitarte, K Sharma, P Madhu, AB Morales-Vilches, PK Nayak, S Bai, F Gao, CRM Grovenor, MB Johnston, JG Labram, JR Durrant, JM Ball, B Wenger, B Stannowski, HJ Snaith

Longevity has been a long-standing concern for hybrid perovskite photovoltaics. We demonstrate high-resilience positive-intrinsic-negative perovskite solar cells by incorporating a piperidinium-based ionic compound into the formamidinium-cesium lead-trihalide perovskite absorber. With the bandgap tuned to be well suited for perovskite-on-silicon tandem cells, this piperidinium additive enhances the open-circuit voltage and cell efficiency. This additive also retards compositional segregation into impurity phases and pinhole formation in the perovskite absorber layer during aggressive aging. Under full-spectrum simulated sunlight in ambient atmosphere, our unencapsulated and encapsulated cells retain 80 and 95% of their peak and post-burn-in efficiencies for 1010 and 1200 hours at 60&#xB0; and 85&#xB0;C, respectively. Our analysis reveals detailed degradation routes that contribute to the failure of aged cells.


Faraday-cage-assisted etching of suspended gallium nitride nanostructures

AIP Advances AIP Publishing 10 (2020) 055319

GP Gough, A Sobiesierski, R Taylor, S Shabbir, S Thomas, DM Beggs, AJ Bennett

We have developed an inductively coupled plasma etching technique using a Faraday cage to create suspended gallium-nitride devices in a single step. The angle of the Faraday cage, gas mix, and chamber condition define the angle of the etch and the cross-sectional profile, which can feature undercut angles of up to 45°. We fabricate singly- and doubly-clamped cantilevers of a triangular cross section and show that they can support single optical modes in the telecom C-band.


Optical shaping of the polarization anisotropy in a laterally coupled quantum dot dimer.

Light, science & applications Springer Science and Business Media LLC 9 (2020) ARTN 100

H Kim, K Kyhm, RA Taylor, JS Kim, JD Song, S Park

We find that the emission from laterally coupled quantum dots is strongly polarized along the coupled direction [1 1&#xAF; 0], and its polarization anisotropy can be shaped by changing the orientation of the polarized excitation. When the nonresonant excitation is linearly polarized perpendicular to the coupled direction [110], excitons (X1 and X2) and local biexcitons (X1X1 and X2X2) from the two separate quantum dots (QD1 and QD2) show emission anisotropy with a small degree of polarization (10%). On the other hand, when the excitation polarization is parallel to the coupled direction [1 1&#xAF; 0], the polarization anisotropy of excitons, local biexcitons, and coupled biexcitons (X1X2) is enhanced with a degree of polarization of 74%. We also observed a consistent anisotropy in the time-resolved photoluminescence. The decay rate of the polarized photoluminescence intensity along the coupled direction is relatively high, but the anisotropic decay rate can be modified by changing the orientation of the polarized excitation. An energy difference is also observed between the polarized emission spectra parallel and perpendicular to the coupled direction, and it increases by up to three times by changing the excitation polarization orientation from [110] to [1 1&#xAF; 0]. These results suggest that the dipole-dipole interaction across the two separate quantum dots is mediated and that the anisotropic wavefunctions of the excitons and biexcitons are shaped by the excitation polarization.


Charge‐Carrier Trapping and Radiative Recombination in Metal Halide Perovskite Semiconductors

Advanced Functional Materials Wiley (2020) 2004312-2004312

MJ Trimpl, AD Wright, K Schutt, LRV Buizza, Z Wang, MB Johnston, HJ Snaith, P Müller‐Buschbaum, LM Herz


Three-dimensional cross-nanowire networks recover full terahertz state.

Science (New York, N.Y.) 368 (2020) 510-513

K Peng, D Jevtics, F Zhang, S Sterzl, DA Damry, MU Rothmann, B Guilhabert, MJ Strain, HH Tan, LM Herz, L Fu, MD Dawson, A Hurtado, C Jagadish, MB Johnston

Terahertz radiation encompasses a wide band of the electromagnetic spectrum, spanning from microwaves to infrared light, and is a particularly powerful tool for both fundamental scientific research and applications such as security screening, communications, quality control, and medical imaging. Considerable information can be conveyed by the full polarization state of terahertz light, yet to date, most time-domain terahertz detectors are sensitive to just one polarization component. Here we demonstrate a nanotechnology-based semiconductor detector using cross-nanowire networks that records the full polarization state of terahertz pulses. The monolithic device allows simultaneous measurements of the orthogonal components of the terahertz electric field vector without cross-talk. Furthermore, we demonstrate the capabilities of the detector for the study of metamaterials.


Metal composition influences optoelectronic quality in mixed-metal lead-tin triiodide perovskite solar absorbers

ENERGY & ENVIRONMENTAL SCIENCE 13 (2020) 1776-1787

MT Klug, RL Milot, JB Patel, T Green, HC Sansom, MD Farrar, AJ Ramadan, S Martani, Z Wang, B Wenger, JM Ball, L Langshaw, A Petrozza, MB Johnston, LM Herz, HJ Snaith

&#xA9; The Royal Society of Chemistry. Current designs for all-perovskite multi-junction solar cells require mixed-metal Pb-Sn compositions to achieve narrower band gaps than are possible with their neat Pb counterparts. The lower band gap range achievable with mixed-metal Pb-Sn perovskites also encompasses the 1.3 to 1.4 eV range that is theoretically ideal for maximising the efficiency of single-junction devices. Here we examine the optoelectronic quality and photovoltaic performance of the ((HC(NH2)2)0.83Cs0.17)(Pb1-ySny)I3 family of perovskite materials across the full range of achievable band gaps by substituting between 0.001% and 70% of the Pb content with Sn. We reveal that a compositional range of "defectiveness"exists when Sn comprises between 0.5% and 20% of the metal content, but that the optoelectronic quality is restored for Sn content between 30-50%. When only 1% of Pb content is replaced by Sn, we find that photoconductivity, photoluminescence lifetime, and photoluminescence quantum efficiency are reduced by at least an order of magnitude, which reveals that a small concentration of Sn incorporation produces trap sites that promote non-radiative recombination in the material and limit photovoltaic performance. While these observations suggest that band gaps between 1.35 and 1.5 eV are unlikely to be useful for optoelectronic applications without countermeasures to improve material quality, highly efficient narrower band gap absorber materials are possible at or below 1.33 eV. Through optimising single-junction photovoltaic devices with Sn compositions of 30% and 50%, we respectively demonstrate a 17.6% efficient solar cell with an ideal single-junction band gap of 1.33 eV and an 18.1% efficient low band gap device suitable for the bottom absorber in all-perovskite multi-junction cells.

Pages