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Gabriel Bernardo

Gabriel Bernardo
FEUP/LEPABE · Chemical Engineering

PhD in Materials Science - Oxford University

About

69
Publications
10,531
Reads
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Citations
Introduction
Gabriel Bernardo currently works at LEPABE (https://www.lepabe.fe.up.pt/) in the Department of Chemical Engineering, University of Porto. Gabriel does research in Materials Science, Polymer Science, Physical-Chemistry and Nanotechnology. He is currently working on the "Upscaling and morphological characterization of polymer photovoltaics" and "Polymer-based carbon membranes for gas purification".
Additional affiliations
December 2017 - present
LEPABE
Position
  • Research Assistant
July 2015 - August 2017
The University of Sheffield
Position
  • Fellow
July 2009 - June 2015
University of Minho
Position
  • Assistant Researcher
Education
October 2001 - September 2005
University of Oxford
Field of study
  • Materials Science

Publications

Publications (69)
Article
Full-text available
Over the last four years, tremendous progress has occurred in the field of organic photovoltaics (OPVs) and the champion power conversion efficiency (PCE) under AM1.5G conditions,as certified by the National Renewable Energy Laboratory (NREL), is currently 18.2%. However,these champion state-of-the-art devices were fabricated at lab-scale using hig...
Article
Full-text available
The impact of several solvent processing additives (1-chloronaphthalene, methylnaphthalene, hexadecane, 1-phenyloctane, and p-anisaldehyde), 3% v/v in o-dichlorobenzene, on the performance and morphology of poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3‴-di(2-octyldodecyl)-2,2′,5′,22033,5″,2‴-quaterthiophen-5,5‴-diyl)] (PffBT4T-2OD):[6...
Article
Perovskite solar cells (PSCs) are an emerging solar cell technology that has shown the fastest growth in power conversion efficiency (PCE). The present power conversion efficiency record of 25.5% is already comparable to crystalline silicon technology, which is attracting the research and industrial community attention. The main challenges in scali...
Article
Carbon molecular sieve membranes (CMSMs) with a remarkable separation performance and stability were prepared from an ionic liquid regenerated cellulose precursor. Extremely high selectivities to H2 and CO2 are reported (H2/CH4 > 206 000 and CO2/CH4 > 14 600) due to the precise pore size of the produced membranes. Selectivity results >3590 are repo...
Article
Full-text available
Organic photovoltaic (OPV) cells have recently undergone a rapid increase in power conversion efficiency (PCE) under AM1.5G conditions, as certified by the National Renewable Energy Laboratory (NREL), which have jumped from 11.5% in October 2017 to 18.2% in December 2020. However, the NREL certified PCE of large area OPV modules is still lagging fa...
Article
Novel carbon adsorbents for propane/propylene separation, with an unprecedented adsorption selectivity to propane – the minority component – were prepared from a phenolic resin precursor. The preparation conditions of the carbon molecular sieve adsorbents, such as pre-treatment with phosphoric acid; carbonization and post-treatment with propylene,...
Article
Full-text available
In a proof‐of‐concept study, this work demonstrates that incorporating a specifically designed block copolymer as an interfacial layer between a charge transport layer and the photoactive layer in organic solar cells can enhance the interface between these layers leading to both performance and stability improvements of the device. This is achieved...
Article
Full-text available
In the field of gas separation and purification, membrane technologies compete with conventional purification processes on the basis of technical, economic and environmental factors. In this context, there is a growing interest in the development of carbon molecular sieve membranes (CMSM) due to their higher permeability and selectivity and higher...
Article
Full-text available
The impact of fullerene side chain functionalization with thiophene and carbazole groups on the device properties of bulk-heterojunction polymer:fullerene solar cells is discussed through a systematic investigation of material blends consisting of the conjugated polymer poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3‴-di(2-octyldodecyl)...
Article
Full-text available
Fullerene derivatives are used in a wide range of applications including as electron acceptors in solution-processable organic photovoltaics. We report agglomeration of fullerene derivatives in optically opaque solutions of PC 61 BM and PC 71 BM, with concentrations ranging from 30 mg mL À1 up to 90 mg mL À1 , in different solvents with relevance t...
Article
The impact of the additive 1,8-diiodooctane on the morphology of bulk-heterojunction solar cells based on the systems P3HT:PC71BM, PTB7:PC71BM and PTB7-Th:PC71BM is studied using a combination of Small Angle Neutron Scattering (SANS) and Atomic Force Microscopy (AFM). The results clearly show that while in the P3HT:PC71BM system, the additive DIO p...
Article
Full-text available
Novel C 60 and C 70 N-methyl-fulleropyrrolidine derivatives, containing both electron withdrawing and electron donating substituent groups, were synthesized by the well-known Prato reaction. The corresponding highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) energy levels were determined by cyclic voltammetry, fro...
Article
Planet Earth is facing accelerated global warming due to greenhouse gas emissions from human activities. The United Nations agreement at the Paris Climate Conference in 2015 highlighted the importance of reducing CO2 emissions from fossil fuel combustion. Hydrogen is a clean and efficient energy carrier and a hydrogen-based economy is now widely re...
Article
Doping poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is known to improve its conductivity; however, little is known about the thin-film structure of PEDOT:PSS when doped with an asymmetrically charged dopant. In this study, PEDOT:PSS was doped with different concentrations of the zwitterion 3-(N,N dimethylmyristylammonio)prop...
Article
Monolithic assembly of dye-sensitized solar cells (M−DSSCs) is technologically attractive due to its ease of fabrication, compactness and lower production cost. However, combining cost-effective materials with high power conversion efficiency in M−DSSCs is still a challenging task. New silica-based spacer layers for M−DSSCs, derived from entirely w...
Article
We investigate the morphological development of polystyrene (PS)-C60 nanocomposites along the length of a prototype co-rotating twin-screw extruder with sampling capabilities. The effects of C60 concentration and output on the morphological evolution along the extruder are studied employing a suite of characterization techniques covering a wide ran...
Article
Full-text available
Organic photovoltaic (OPV) devices, made with semiconducting polymers, have recently attained a power conversion efficiency (PCE) over 14% in single junction cells and over 17% in tandem cells. These high performances, together with the suitability of the technology to inexpensive large-scale manufacture, over lightweight and flexible plastic subst...
Article
A hermetic laser-assisted glass frit encapsulation, at process temperature of 120 °C, was developed for perovskite solar cell application. The hermeticity and long-term stability of the sealing was examined based on standard tests for photovoltaic applications. Encapsulations using FTO (Fluorine doped Tin Oxide) coated glass substrates displayed 8....
Article
Full-text available
1,8-Diiodooctane (DIO) is an additive used in the processing of organic photovoltaics and has previously been reported, on the basis of small-angle X-ray scattering (SAXS) measurements, to deflocculate nano-aggregates of [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) in chlorobenzene. We have critically re-examined this finding in a series of...
Article
Full-text available
We have studied bulk-heterojunction (BHJ) solar cells composed of the polymer PffBT4T-2OD as electron donor and three different electron accepting fullerenes, namely PC71BM, PC61BM and indene-C60-bis-adduct (ICBA) in order to understand the impact of different fullerenes on the morphology and efficiency of the corresponding photovoltaic devices. De...
Article
Full-text available
The impact of PC61BM and PC71BM on the thermal stability of two low-bandgap conjugated polymers widely used in organic photovoltaic applications, namely PTB7 and PTB7-Th (also known as PBDTTT-EFT), was studied under nitrogen and air atmospheres. The thermal stability effect observed is mainly additive, i.e., the stability of the composites is simil...
Article
We investigated the effect of the feeding formulation (premixed powders of pure components versus solvent-blended mixture) of polystyrene–C60 composites on the dispersion and reagglomeration phenomena developing along the barrel of a twin-screw extruder. The dispersion of C60 in the PS matrix is studied over different length scales using a combinat...
Article
Full-text available
We demonstrate that the inclusion of a small amount of the co-solvent 1,8-diiodooctane in the preparation of a bulk-heterojunction photovoltaic device increases its power conversion efficiency by 20%, through a mechanism of transient plasticisation. We follow the removal of 1,8-diiodooctane directly after spin-coating using ellipsometry and ion bea...
Article
The phase behavior of [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blends with amorphous polymers with different degrees of aromaticity has been investigated by differential scanning calorimetry (DSC) and small-angle neutron scattering (SANS). The polymers investigated are the homologous series of polystyrene (PS), poly(2-vinyl-naphthalene) (P...
Article
Full-text available
The thermal stability of poly(methyl methacrylate) (PMMA) composites with the two fullerenes C60 and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), was studied over the whole composition range under nitrogen (N2) and air atmosphere using dynamic thermogravimetric analysis (TGA). The aim of this study was to compare the thermal stabilization eff...
Chapter
Fluorescence spectroscopy is a technique that allows the study of structural, morphological and dynamic phenomena in polymer systems and which has been used for decades in the study of polymer blends. The technique is particularly attractive due to its high sensitivity, with very low detection limits, allowing information to be obtained with both v...
Article
The molecular mobility of polymers in their solid or molten states allows their processing without the need for toxic, “non-friendly” solvents. In this work, the main features of solvent-free processing methods applied to conjugated polymers are reviewed taking into consideration that these materials are largely used in a broad range of (opto-)elec...
Article
Full-text available
Ribbons of poly(3-hexylthiophene) (P3HT) 0.15 and 0.30 mm thickness were extruded at the temperatures of 200 and 250 °C, i.e., below and above the melting temperature of P3HT (∼240 °C), using a small home-made extrusion device. The ribbons produced by this method are continuous and freestanding. WAXS results show that all the extruded samples are m...
Article
Full-text available
Activated anionic ring-opening polymerization of e-caprolactam (ECL) was carried out for the first time in the presence of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) to prepare polyamide 6 (PA6)-based composites comprising up to 3 wt% of this fullerene derivative. This in situ polymerization process produced high molecular weight composites...
Data
a b s t r a c t The thermal stability of poly(3-hexylthiophene) (P3HT) in its molten state was investi-gated in air and nitrogen atmospheres under no illumination conditions, with the aim of testing the feasibility of processing it using polymer melt techniques. A large set of different experimental characterization techniques was used including th...
Data
Fibers of pure poly(3-hexylthiophene) (P3HT) of 1 and 2 mm diameter, were produced from solid state processing at temperatures of 200, 150 and 100ºC, i.e. up to more than 100 ºC below the melting point of P3HT (∼240 ºC), using a small device reminiscent with the early stage polymer extrusion machines. The fibers produced by this method are continuo...
Article
Gravimetry is used to study the diffusion of a homologous series of alcohols (Cn, with n = 1, 2, 3, 4, 6, 10, and 16) in amorphous polystyrene at temperatures from 35 to 145 ºC, that is both below and above the polymer glass transition temperature of 100 ºC. All the mass uptake results are well described by a simple Fickian model (for t < t1/2) and...
Article
Full-text available
Blends of Si nanocrystals (Si-NCs) and organic semiconductors are promising materials for new optical and electronic devices processed from solutions. Here, we study how the optical properties of composite films containing Si-NCs and the organic semiconductor poly(3-hexylthiophene) (P3HT) are influenced by the composition and morphology resulting f...
Article
Full-text available
This work deals with an experimental investigation of the microstructure/morphology of spin-casted composite thin films of poly(3-hexylthiophene) (P3HT) and silicon nanocrystals (Si- NCs), in the weight proportion 1:1, which develop under different deposition conditions. The experimental parameters considered were the following: i) solvent quality;...
Article
Full-text available
Gravimetry is used to study the diffusivity of a homologous series of linear alkanes (Cn, with n = 8, 10, 12, 14 and 16) in amorphous polystyrene at temperatures ranging from 45 °C to 145 °C, i.e. both below and above the polymer glass transition temperature (100 °C). All the mass uptake results obtained are well described by a simple Fickian model...
Chapter
Full-text available
In this work we have performed a systematic study of blends of [6,6]-phenyl C61 butyric acid methyl ester (PCBM) with the following amorphous and semi-crystalline polymers: atactic polystyrene (PS), syndiotactic polystyrene (syn-PS), poly(2-vinyl-naphthalene) (P2VN), poly(9-vinyl-phenanthrene) (P9VPh), poly(vinylidene-fluoride) (PVdF) and poly(3-he...
Article
Gravimetry was used to study the diffusion of a homologous series of linear carboxylic acids (Cn, with n = 2, 6–16) in amorphous polystyrene at temperatures from 35 °C to 165 °C, that is, both below and above the polymer glass transition temperature of 100 °C. All the mass uptake results are well described by a simple Fickian model (for t < t1/2) a...
Article
Full-text available
In this work we have performed a systematic study of blends of [6,6]-phenyl C61 butyric acid methyl ester (PCBM) with the following amorphous and semi-crystalline polymers: atactic polystyrene (PS), syndiotactic polystyrene (syn-PS), poly(2-vinyl-naphthalene) (P2VN), poly(9-vinyl-phenanthrene) (P9VPh), poly(vinylidene-fluoride) (PVdF) and poly(3-he...
Article
This work describes the use of current-sensing atomic force microscopy and dynamic scaling laws to characterize the surface morphologies of polymer light-emitting diode interlayers formed by poly(9,9-dioctylfluorene), PFO, on top of poly(3,4-ethylene dioxythiophene) doped with poly(styrene sulfonic acid), PEDOT:PSS. Two types of PFO differing in mo...
Article
Full-text available
Light-emitting diodes based on blends of the two green-emitting polymers, poly(9,9-dioctylfluorene-alt-benzothiadiazole), F8BT, and poly(9,9-dioctylfluorene-alt-bithiophene), F8T2, show efficiencies that lie in between those of the devices based on the neat polymers (with a maximum efficiency of approximately 4 cd/A for the devices with magnesium c...
Article
Light-emitting diodes (LEDs), based on blue-emitting polyfluorenes are usually prone to the appearance of a contaminant green emission (centered around 520nm), leading to an apparent whitish light emission. We find that, for LEDs based on poly(9,9-dioctylfluorene), PFO, the blending with the hole transporting polyvinylcarbazole, PVK, can suppress s...
Article
Swelling behavior of a commercial linear polystyrene, containing a small amount (<5% wt) of mineral oil, has been studied in three different classes of organic solvents (alkanes, alcohols and carboxylic acids) using both gravimetry and light microscopy. A comparison has been made with the results presented in earlier publications using a different...
Article
The authors report on the performance of polymer-based light-emitting diodes, LEDs, using amorphous zinc oxide-doped indium oxide, IZO, as anode. In particular, LEDs with poly[(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] as electroluminescent layer and aluminium cathodes, show higher efficiency with this IZO anode (0.015 cd/A) than with...
Article
In this study, we show that the equilibrium saturation swelling of polystyrene by linear alkanes and linear carboxylic acids, as reported earlier (Bernardo and Vesely, Eur Polym J 2007, 43, 4983, Bernardo and Vesely, J Appl Polym Sci 2008, 110, 2393) can be correlated quantitatively using a model where only the alkyl-chain lengths and the saturated...
Article
The solubilities of seven alkanes in a matrix of uncrosslinked polystyrene were measured at several different temperatures. A gravimetric method reported earlier was used to monitor the sorption of the solvents. The experimental measurements showed unambiguously that the solubility of the alkanes diffusing into a polystyrene matrix reached a consta...
Article
Novel electroluminescent materials combining three functionalities were used as active layers in light-emitting diodes. These functionalities are brought about by the presence of three moieties: diphenylstylbeneamines, for hole transport, quinoxaline, for electron-transport, and a dehydroabietic acid methyl ester, to prevent crystallisation. The de...
Article
Full-text available
The effect of very thin polymer interlayers made of either acid-initiated cross-linkable polyfluorenes or the parent non-cross-linkable polyfluorenes, on top of poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid, on the efficiency of light-emitting diodes based on three different electroluminescent (EL) polymers is studied. We fi...
Article
Solubility diagrams of a series of carboxylic acids in a matrix of linear polystyrene have been measured using a gravimetric method on samples immersed in solvent, as reported earlier [Bernardo G, Vesely D. Eur Polym J 2007;43:938–48]. The results show that the amount of solvent, swelling the polymer, reaches an equilibrium saturation which has a u...
Article
Full-text available
The efficiency of light-emitting diodes based on poly[(2-methoxy)-5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene] increases upon formation of interlayers, on top of poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid (PEDOT:PSS), made of acid-initiated cross-linkable polyfluorenes. The use of this type of polymers allows for the form...
Article
The solubility of alcohols in a polystyrene matrix during the diffusion process was measured by a gravimetric technique. It is shown that the amount of solvent swelling the polymer reaches an equilibrium saturation, which is dependent on the system and temperature, but independent on the sample preparation. Phase diagrams, similar to those measured...
Chapter
Full-text available
The density functional theory and the cluster model approach enable the quantitative computational analysis of the adsorption of small chemical species on metal surfaces. Two studies are presented, one concerning the adsorption of acetylene on copper (100) surfaces, the other concerning the adsorption of ethylene on the (100) surfaces of nickel, pa...
Article
The density functional theory and the cluster model approach have been used to study the adsorption of the acetylene molecule on the (100) surface of copper. Five possible adsorption sites have been considered: parallel twofold bridge, perpendicular twofold bridge, threefold hollow, diagonal fourfold hollow and aligned fourfold hollow sites. For ea...
Article
Density functional theory calculations have been performed for the adsorption of the ethylene molecule on the (110) surfaces of platinum, silver and copper. The cluster model approach has been used to model the metal surfaces. For each metal surface, four adsorption sites have been considered: the atop site, the shortbridge site, the longbridge sit...
Article
The density functional theory and the cluster model approach have been used to study the adsorption of the ethylene molecule on the (100) surfaces of platinum, palladium and nickel. For each metal surface, two adsorption sites have been considered: the atop site (π) and the bridge site (di-σ). For each case, optimized geometries, adsorption energie...

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