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Papers by Paul Winget

SID Symposium Digest of Technical Papers

This work discusses how some of Schrödinger's latest innovations in digital chemical simulati... more This work discusses how some of Schrödinger's latest innovations in digital chemical simulation accelerate materials discovery in displays. We will describe simulation tools to explore OLED materials degradation, film morphology from evaporative and solution molecular deposition, spectral predictions for light‐emitting processes, and excited state energy transfer.

clicking here. colleagues, clients, or customers by , you can order high-quality copies for your ... more clicking here. colleagues, clients, or customers by , you can order high-quality copies for your If you wish to distribute this article to others here. following the guidelines can be obtained by Permission to republish or repurpose articles or portions of articles ): May 7, 2012 www.sciencemag.org (this information is current as of The following resources related to this article are available online at

Sid's Digest Of Technical Papers, Jun 1, 2022

This work demonstrates an active learning (AL) workflow for identifying promising material candid... more This work demonstrates an active learning (AL) workflow for identifying promising material candidates for organic lightemitting diodes (OLEDs) based on multiple optoelectronic parameters while minimizing the number of physics‐based computations to explore an extensive library. This work paves the way for efficient computational materials screening before laborious synthesis, and device fabrication.

Molecular Pharmaceutics, Sep 27, 2021

Amorphous solid dispersions (ASDs) are commonly used to orally deliver small-molecule drugs that ... more Amorphous solid dispersions (ASDs) are commonly used to orally deliver small-molecule drugs that are poorly water-soluble. ASDs consist of drug molecules in the amorphous form which are dispersed in a hydrophilic polymer matrix. Producing a high-performance ASD is critical for effective drug delivery and depends on many factors such as solubility of the drug in the matrix and the rate of drug release in aqueous medium (dissolution), which is linked to bioperformance. Often, researchers perform a large number of design iterations to achieve this objective. A detailed molecular-level understanding of the mechanisms behind ASD dissolution behavior would aid in the screening, designing, and optimization of ASD formulations and would minimize the need for testing a wide variety of prototype formulations. Molecular dynamics and related types of simulations, which model the collective behavior of molecules in condensed phase systems, can provide unique insights into these mechanisms. To study the effectiveness of these simulation techniques in ASD formulation dissolution, we carried out dissipative particle dynamics simulations, which are particularly an efficient form of molecular dynamics calculations. We studied two stages of the dissolution process: the early-stage of the dissolution process, which focuses on the dissolution at the ASD/water interface, and the late-stage of the dissolution process, where significant drug release would have occurred and there would be a mixture of drug and polymer molecules in a predominantly aqueous environment. Experimentally, we used Fourier transform infrared spectroscopy to study the interactions between drugs, polymers, and water in the dry and wet states and the chromatographic technique to study the rate of drug and polymer release. Both experiments and simulations provided evidence of polymer microstructures and drug-polymer interactions as important factors for the dissolution behavior of the investigated ASDs, consistent with previous work by Pudlas et al. (Eur. J. Pharm. Sci. 2015, 67, 21-31). As experimental and simulation results are consistent and complementary, it is clear that there is significant potential for combined experimental and computational research for a detailed understanding of ASD formulations and, hence, formulation optimization.

Sid's Digest Of Technical Papers, Apr 1, 2023

We have entered a paradigm-changing era in the way chemists innovate. Many fields, such as automo... more We have entered a paradigm-changing era in the way chemists innovate. Many fields, such as automotive engineering and particle physics, rely today on accurate simulation before experimentation. In recent years, chemistry has entered a new phase of chemical solution design powered by a rich set of physics-based and augmented intelligence capabilities. This talk will present select case studies illustrating some of our latest physics-based simulation technology for developing and optimizing OLED materials. We will also introduce an enterprise informatics platform (LiveDesignTM) focused on chemical discovery, enabling multidisciplinary teams to amplify their development cycle with collaboration on a global scale.

Chemistry of Materials, Apr 12, 2017

N-Heterocyclic carbenes (NHCs) bind strongly to gold and other metals. This work experimentally p... more N-Heterocyclic carbenes (NHCs) bind strongly to gold and other metals. This work experimentally probes the effect of NHCs on the work function (WF) of gold for the first time, theoretically analyzes the origin of this effect, and examines the effectiveness of NHC-modified gold as an electron-injecting electrode. UV photoelectron spectroscopy shows the WF of planar gold is reduced by nearly 2 eV to values of 3.3−3.5 eV. This effect is seen for NHCs with various heterocyclic cores, and with either small or large N,N′substituents. DFT calculations indicate the WF reduction results from both the interface dipole formed between the NHC and the gold and from the NHC molecular dipole. For N,N′-diisopropyl-NHCs, an important contributor to the former is charge transfer associated with coordination of the carbene carbon atom to gold. In contrast, the carbene carbon of N,N′-2,6-diisopropylphenyl-NHCs is not covalently bound to gold, resulting in a lower interface dipole; however, a larger molecular dipole partially compensates for this. Single-layer C 60 diodes with NHC-modified gold as the bottom electrode demonstrate high rectification ratios and show that these electrodes can act as effective electron-injecting contacts, suggesting they may be useful for a variety of materials applications.

Science and Technology of Advanced Materials, Aug 1, 2014

Solid oxide fuel cells (SOFCs) efficiently generate electricity, but high operating temperatures ... more Solid oxide fuel cells (SOFCs) efficiently generate electricity, but high operating temperatures (T op > 800°C) limit their utility. Reducing T op requires mixed ion-electron conducting (MIEC) cathode materials. Density functional theory is used here to investigate the role of potassium substitutions in the MIEC material Sr 1−x K x FeO 3 (SKFO). We predict that such substitutions are endothermic. SrFeO 3 and SKFO have nearly identical metallic electronic structures. Oxygen vacancy formation energies decrease by ∼0.2 eV when x K increases from 0 to 0.0625. SKFO is a promising SOFC MIEC cathode material; however, further experimental investigations must assess its long-term stability at the desired operating temperatures.

Acs Symposium Series, Jun 14, 2022

We present eight new parameterizations of the SM5.42R solvation model: in particular we present p... more We present eight new parameterizations of the SM5.42R solvation model: in particular we present parameterizations for HF/MIDI!, HF/6-31G*, HF/6- 31+G*, HF/cc-pVDZ, AM1, PM3, BPW91/MIDI!, and B3LYP/MIDI!. Two of the new cases are parameterized using the reaction-field operator presented previously, and six of the new cases are parameterized with a simplified reaction-field operator; results obtained by the two methods are compared for selected examples. For a training set of 2135 data for 275 neutral solutes contain- ing H, C, N, O, F, S, P, Cl, Br, and I in 91 solvents (water and 90 nonaqueous solvents), seven of the eight new parameterizations give mean unsigned errors in the range 0.43-0.46 kcal/mol, and the eighth - for a basis set containing diÄuse functions - gives a mean unsigned error of 0.53 kcal/mol. The mean unsigned error for 49 ionic solutes (containing the same elements) in water is 3.5-3.9 kcal/mol for the Hartree-Fock, Becke-Perdew- Wang-1991 and Becke three-parameter Lee-Yang-Parr cases and 4.1 and 4.0 kcal/mol for parameterized model 3 and Austin model 1, respectively. The methods are tested for sensitivity of solvation free energies to geometry and for predicting partition coeÅcients of carbonates, which were not included in the training set.

SID Symposium Digest of Technical Papers

We have entered a paradigm-changing era in the way chemists innovate. Many fields, such as automo... more We have entered a paradigm-changing era in the way chemists innovate. Many fields, such as automotive engineering and particle physics, rely today on accurate simulation before experimentation. In recent years, chemistry has entered a new phase of chemical solution design powered by a rich set of physics-based and augmented intelligence capabilities. This talk will present select case studies illustrating some of our latest physics-based simulation technology for developing and optimizing OLED materials. We will also introduce an enterprise informatics platform (LiveDesignTM) focused on chemical discovery, enabling multidisciplinary teams to amplify their development cycle with collaboration on a global scale.

SID Symposium Digest of Technical Papers

This work demonstrates an active learning (AL) workflow for identifying promising material candid... more This work demonstrates an active learning (AL) workflow for identifying promising material candidates for organic lightemitting diodes (OLEDs) based on multiple optoelectronic parameters while minimizing the number of physics‐based computations to explore an extensive library. This work paves the way for efficient computational materials screening before laborious synthesis, and device fabrication.

Molecular Pharmaceutics, 2021

Amorphous solid dispersions (ASDs) are commonly used to orally deliver small-molecule drugs that ... more Amorphous solid dispersions (ASDs) are commonly used to orally deliver small-molecule drugs that are poorly water-soluble. ASDs consist of drug molecules in the amorphous form which are dispersed in a hydrophilic polymer matrix. Producing a high-performance ASD is critical for effective drug delivery and depends on many factors such as solubility of the drug in the matrix and the rate of drug release in aqueous medium (dissolution), which is linked to bioperformance. Often, researchers perform a large number of design iterations to achieve this objective. A detailed molecular-level understanding of the mechanisms behind ASD dissolution behavior would aid in the screening, designing, and optimization of ASD formulations and would minimize the need for testing a wide variety of prototype formulations. Molecular dynamics and related types of simulations, which model the collective behavior of molecules in condensed phase systems, can provide unique insights into these mechanisms. To study the effectiveness of these simulation techniques in ASD formulation dissolution, we carried out dissipative particle dynamics simulations, which are particularly an efficient form of molecular dynamics calculations. We studied two stages of the dissolution process: the early-stage of the dissolution process, which focuses on the dissolution at the ASD/water interface, and the late-stage of the dissolution process, where significant drug release would have occurred and there would be a mixture of drug and polymer molecules in a predominantly aqueous environment. Experimentally, we used Fourier transform infrared spectroscopy to study the interactions between drugs, polymers, and water in the dry and wet states and the chromatographic technique to study the rate of drug and polymer release. Both experiments and simulations provided evidence of polymer microstructures and drug-polymer interactions as important factors for the dissolution behavior of the investigated ASDs, consistent with previous work by Pudlas et al. (Eur. J. Pharm. Sci. 2015, 67, 21-31). As experimental and simulation results are consistent and complementary, it is clear that there is significant potential for combined experimental and computational research for a detailed understanding of ASD formulations and, hence, formulation optimization.

Chemistry of Materials, 2017

N-Heterocyclic carbenes (NHCs) bind strongly to gold and other metals. This work experimentally p... more N-Heterocyclic carbenes (NHCs) bind strongly to gold and other metals. This work experimentally probes the effect of NHCs on the work function (WF) of gold for the first time, theoretically analyzes the origin of this effect, and examines the effectiveness of NHC-modified gold as an electron-injecting electrode. UV photoelectron spectroscopy shows the WF of planar gold is reduced by nearly 2 eV to values of 3.3−3.5 eV. This effect is seen for NHCs with various heterocyclic cores, and with either small or large N,N′substituents. DFT calculations indicate the WF reduction results from both the interface dipole formed between the NHC and the gold and from the NHC molecular dipole. For N,N′-diisopropyl-NHCs, an important contributor to the former is charge transfer associated with coordination of the carbene carbon atom to gold. In contrast, the carbene carbon of N,N′-2,6-diisopropylphenyl-NHCs is not covalently bound to gold, resulting in a lower interface dipole; however, a larger molecular dipole partially compensates for this. Single-layer C 60 diodes with NHC-modified gold as the bottom electrode demonstrate high rectification ratios and show that these electrodes can act as effective electron-injecting contacts, suggesting they may be useful for a variety of materials applications.

Journal of physics. Condensed matter : an Institute of Physics journal, Jan 12, 2016

The electronic structure of inorganic semiconductor interfaces functionalized with extended π-con... more The electronic structure of inorganic semiconductor interfaces functionalized with extended π-conjugated organic molecules can be strongly influenced by localized gap states or point defects, often present at low concentrations and hard to identify spectroscopically. At the same time, in transparent conductive oxides such as ZnO, the presence of these gap states conveys the desirable high conductivity necessary for function as electron-selective interlayer or electron collection electrode in organic optoelectronic devices. Here, we report on the direct spectroscopic detection of a donor state within the band gap of highly conductive zinc oxide by two-photon photoemission spectroscopy. We show that adsorption of the prototypical organic acceptor C60 quenches this state by ground-state charge transfer, with immediate consequences on the interfacial energy level alignment. Comparison with computational results suggests the identity of the gap state as a near-surface-confined oxygen vac...

Chemistry of Materials, 2015

We present a comprehensive investigation, via first-principles density functional theory 2 (DFT) ... more We present a comprehensive investigation, via first-principles density functional theory 2 (DFT) calculations, of various surface terminations of magnetite, Fe 3 O 4 (111), a major 3 iron oxide which has also a number of applications in electronics and spintronics. We 4 compare the thermodynamic stability and electronic structure among the different 5 surfaces terminations. Interestingly, we find that surfaces modified with point defects 6 and adatoms are close in surface energy and in the oxygen-rich and oxygen-poor 7 regimes can be more stable than bulk-like terminations. These surfaces show different 8

SID Symposium Digest of Technical Papers

Organic light‐emitting diodes (OLEDs) are fabricated using a stepwise process, where layers are d... more Organic light‐emitting diodes (OLEDs) are fabricated using a stepwise process, where layers are deposited on top of previous layers. Each of these deposition steps introduces changes to the film structure, both in the crystal structure and in the growth direction. These changes in film structure have dramatic influences on the overall performance of practical devices.

SID Symposium Digest of Technical Papers

This work discusses how some of Schrödinger's latest innovations in digital chemical simulati... more This work discusses how some of Schrödinger's latest innovations in digital chemical simulation accelerate materials discovery in displays. We will describe simulation tools to explore OLED materials degradation, film morphology from evaporative and solution molecular deposition, spectral predictions for light‐emitting processes, and excited state energy transfer.

clicking here. colleagues, clients, or customers by , you can order high-quality copies for your ... more clicking here. colleagues, clients, or customers by , you can order high-quality copies for your If you wish to distribute this article to others here. following the guidelines can be obtained by Permission to republish or repurpose articles or portions of articles ): May 7, 2012 www.sciencemag.org (this information is current as of The following resources related to this article are available online at

Sid's Digest Of Technical Papers, Jun 1, 2022

This work demonstrates an active learning (AL) workflow for identifying promising material candid... more This work demonstrates an active learning (AL) workflow for identifying promising material candidates for organic lightemitting diodes (OLEDs) based on multiple optoelectronic parameters while minimizing the number of physics‐based computations to explore an extensive library. This work paves the way for efficient computational materials screening before laborious synthesis, and device fabrication.

Molecular Pharmaceutics, Sep 27, 2021

Amorphous solid dispersions (ASDs) are commonly used to orally deliver small-molecule drugs that ... more Amorphous solid dispersions (ASDs) are commonly used to orally deliver small-molecule drugs that are poorly water-soluble. ASDs consist of drug molecules in the amorphous form which are dispersed in a hydrophilic polymer matrix. Producing a high-performance ASD is critical for effective drug delivery and depends on many factors such as solubility of the drug in the matrix and the rate of drug release in aqueous medium (dissolution), which is linked to bioperformance. Often, researchers perform a large number of design iterations to achieve this objective. A detailed molecular-level understanding of the mechanisms behind ASD dissolution behavior would aid in the screening, designing, and optimization of ASD formulations and would minimize the need for testing a wide variety of prototype formulations. Molecular dynamics and related types of simulations, which model the collective behavior of molecules in condensed phase systems, can provide unique insights into these mechanisms. To study the effectiveness of these simulation techniques in ASD formulation dissolution, we carried out dissipative particle dynamics simulations, which are particularly an efficient form of molecular dynamics calculations. We studied two stages of the dissolution process: the early-stage of the dissolution process, which focuses on the dissolution at the ASD/water interface, and the late-stage of the dissolution process, where significant drug release would have occurred and there would be a mixture of drug and polymer molecules in a predominantly aqueous environment. Experimentally, we used Fourier transform infrared spectroscopy to study the interactions between drugs, polymers, and water in the dry and wet states and the chromatographic technique to study the rate of drug and polymer release. Both experiments and simulations provided evidence of polymer microstructures and drug-polymer interactions as important factors for the dissolution behavior of the investigated ASDs, consistent with previous work by Pudlas et al. (Eur. J. Pharm. Sci. 2015, 67, 21-31). As experimental and simulation results are consistent and complementary, it is clear that there is significant potential for combined experimental and computational research for a detailed understanding of ASD formulations and, hence, formulation optimization.

Sid's Digest Of Technical Papers, Apr 1, 2023

We have entered a paradigm-changing era in the way chemists innovate. Many fields, such as automo... more We have entered a paradigm-changing era in the way chemists innovate. Many fields, such as automotive engineering and particle physics, rely today on accurate simulation before experimentation. In recent years, chemistry has entered a new phase of chemical solution design powered by a rich set of physics-based and augmented intelligence capabilities. This talk will present select case studies illustrating some of our latest physics-based simulation technology for developing and optimizing OLED materials. We will also introduce an enterprise informatics platform (LiveDesignTM) focused on chemical discovery, enabling multidisciplinary teams to amplify their development cycle with collaboration on a global scale.

Chemistry of Materials, Apr 12, 2017

N-Heterocyclic carbenes (NHCs) bind strongly to gold and other metals. This work experimentally p... more N-Heterocyclic carbenes (NHCs) bind strongly to gold and other metals. This work experimentally probes the effect of NHCs on the work function (WF) of gold for the first time, theoretically analyzes the origin of this effect, and examines the effectiveness of NHC-modified gold as an electron-injecting electrode. UV photoelectron spectroscopy shows the WF of planar gold is reduced by nearly 2 eV to values of 3.3−3.5 eV. This effect is seen for NHCs with various heterocyclic cores, and with either small or large N,N′substituents. DFT calculations indicate the WF reduction results from both the interface dipole formed between the NHC and the gold and from the NHC molecular dipole. For N,N′-diisopropyl-NHCs, an important contributor to the former is charge transfer associated with coordination of the carbene carbon atom to gold. In contrast, the carbene carbon of N,N′-2,6-diisopropylphenyl-NHCs is not covalently bound to gold, resulting in a lower interface dipole; however, a larger molecular dipole partially compensates for this. Single-layer C 60 diodes with NHC-modified gold as the bottom electrode demonstrate high rectification ratios and show that these electrodes can act as effective electron-injecting contacts, suggesting they may be useful for a variety of materials applications.

Science and Technology of Advanced Materials, Aug 1, 2014

Solid oxide fuel cells (SOFCs) efficiently generate electricity, but high operating temperatures ... more Solid oxide fuel cells (SOFCs) efficiently generate electricity, but high operating temperatures (T op > 800°C) limit their utility. Reducing T op requires mixed ion-electron conducting (MIEC) cathode materials. Density functional theory is used here to investigate the role of potassium substitutions in the MIEC material Sr 1−x K x FeO 3 (SKFO). We predict that such substitutions are endothermic. SrFeO 3 and SKFO have nearly identical metallic electronic structures. Oxygen vacancy formation energies decrease by ∼0.2 eV when x K increases from 0 to 0.0625. SKFO is a promising SOFC MIEC cathode material; however, further experimental investigations must assess its long-term stability at the desired operating temperatures.

Acs Symposium Series, Jun 14, 2022

We present eight new parameterizations of the SM5.42R solvation model: in particular we present p... more We present eight new parameterizations of the SM5.42R solvation model: in particular we present parameterizations for HF/MIDI!, HF/6-31G*, HF/6- 31+G*, HF/cc-pVDZ, AM1, PM3, BPW91/MIDI!, and B3LYP/MIDI!. Two of the new cases are parameterized using the reaction-field operator presented previously, and six of the new cases are parameterized with a simplified reaction-field operator; results obtained by the two methods are compared for selected examples. For a training set of 2135 data for 275 neutral solutes contain- ing H, C, N, O, F, S, P, Cl, Br, and I in 91 solvents (water and 90 nonaqueous solvents), seven of the eight new parameterizations give mean unsigned errors in the range 0.43-0.46 kcal/mol, and the eighth - for a basis set containing diÄuse functions - gives a mean unsigned error of 0.53 kcal/mol. The mean unsigned error for 49 ionic solutes (containing the same elements) in water is 3.5-3.9 kcal/mol for the Hartree-Fock, Becke-Perdew- Wang-1991 and Becke three-parameter Lee-Yang-Parr cases and 4.1 and 4.0 kcal/mol for parameterized model 3 and Austin model 1, respectively. The methods are tested for sensitivity of solvation free energies to geometry and for predicting partition coeÅcients of carbonates, which were not included in the training set.

SID Symposium Digest of Technical Papers

We have entered a paradigm-changing era in the way chemists innovate. Many fields, such as automo... more We have entered a paradigm-changing era in the way chemists innovate. Many fields, such as automotive engineering and particle physics, rely today on accurate simulation before experimentation. In recent years, chemistry has entered a new phase of chemical solution design powered by a rich set of physics-based and augmented intelligence capabilities. This talk will present select case studies illustrating some of our latest physics-based simulation technology for developing and optimizing OLED materials. We will also introduce an enterprise informatics platform (LiveDesignTM) focused on chemical discovery, enabling multidisciplinary teams to amplify their development cycle with collaboration on a global scale.

SID Symposium Digest of Technical Papers

This work demonstrates an active learning (AL) workflow for identifying promising material candid... more This work demonstrates an active learning (AL) workflow for identifying promising material candidates for organic lightemitting diodes (OLEDs) based on multiple optoelectronic parameters while minimizing the number of physics‐based computations to explore an extensive library. This work paves the way for efficient computational materials screening before laborious synthesis, and device fabrication.

Molecular Pharmaceutics, 2021

Amorphous solid dispersions (ASDs) are commonly used to orally deliver small-molecule drugs that ... more Amorphous solid dispersions (ASDs) are commonly used to orally deliver small-molecule drugs that are poorly water-soluble. ASDs consist of drug molecules in the amorphous form which are dispersed in a hydrophilic polymer matrix. Producing a high-performance ASD is critical for effective drug delivery and depends on many factors such as solubility of the drug in the matrix and the rate of drug release in aqueous medium (dissolution), which is linked to bioperformance. Often, researchers perform a large number of design iterations to achieve this objective. A detailed molecular-level understanding of the mechanisms behind ASD dissolution behavior would aid in the screening, designing, and optimization of ASD formulations and would minimize the need for testing a wide variety of prototype formulations. Molecular dynamics and related types of simulations, which model the collective behavior of molecules in condensed phase systems, can provide unique insights into these mechanisms. To study the effectiveness of these simulation techniques in ASD formulation dissolution, we carried out dissipative particle dynamics simulations, which are particularly an efficient form of molecular dynamics calculations. We studied two stages of the dissolution process: the early-stage of the dissolution process, which focuses on the dissolution at the ASD/water interface, and the late-stage of the dissolution process, where significant drug release would have occurred and there would be a mixture of drug and polymer molecules in a predominantly aqueous environment. Experimentally, we used Fourier transform infrared spectroscopy to study the interactions between drugs, polymers, and water in the dry and wet states and the chromatographic technique to study the rate of drug and polymer release. Both experiments and simulations provided evidence of polymer microstructures and drug-polymer interactions as important factors for the dissolution behavior of the investigated ASDs, consistent with previous work by Pudlas et al. (Eur. J. Pharm. Sci. 2015, 67, 21-31). As experimental and simulation results are consistent and complementary, it is clear that there is significant potential for combined experimental and computational research for a detailed understanding of ASD formulations and, hence, formulation optimization.

Chemistry of Materials, 2017

N-Heterocyclic carbenes (NHCs) bind strongly to gold and other metals. This work experimentally p... more N-Heterocyclic carbenes (NHCs) bind strongly to gold and other metals. This work experimentally probes the effect of NHCs on the work function (WF) of gold for the first time, theoretically analyzes the origin of this effect, and examines the effectiveness of NHC-modified gold as an electron-injecting electrode. UV photoelectron spectroscopy shows the WF of planar gold is reduced by nearly 2 eV to values of 3.3−3.5 eV. This effect is seen for NHCs with various heterocyclic cores, and with either small or large N,N′substituents. DFT calculations indicate the WF reduction results from both the interface dipole formed between the NHC and the gold and from the NHC molecular dipole. For N,N′-diisopropyl-NHCs, an important contributor to the former is charge transfer associated with coordination of the carbene carbon atom to gold. In contrast, the carbene carbon of N,N′-2,6-diisopropylphenyl-NHCs is not covalently bound to gold, resulting in a lower interface dipole; however, a larger molecular dipole partially compensates for this. Single-layer C 60 diodes with NHC-modified gold as the bottom electrode demonstrate high rectification ratios and show that these electrodes can act as effective electron-injecting contacts, suggesting they may be useful for a variety of materials applications.

Journal of physics. Condensed matter : an Institute of Physics journal, Jan 12, 2016

The electronic structure of inorganic semiconductor interfaces functionalized with extended π-con... more The electronic structure of inorganic semiconductor interfaces functionalized with extended π-conjugated organic molecules can be strongly influenced by localized gap states or point defects, often present at low concentrations and hard to identify spectroscopically. At the same time, in transparent conductive oxides such as ZnO, the presence of these gap states conveys the desirable high conductivity necessary for function as electron-selective interlayer or electron collection electrode in organic optoelectronic devices. Here, we report on the direct spectroscopic detection of a donor state within the band gap of highly conductive zinc oxide by two-photon photoemission spectroscopy. We show that adsorption of the prototypical organic acceptor C60 quenches this state by ground-state charge transfer, with immediate consequences on the interfacial energy level alignment. Comparison with computational results suggests the identity of the gap state as a near-surface-confined oxygen vac...

Chemistry of Materials, 2015

We present a comprehensive investigation, via first-principles density functional theory 2 (DFT) ... more We present a comprehensive investigation, via first-principles density functional theory 2 (DFT) calculations, of various surface terminations of magnetite, Fe 3 O 4 (111), a major 3 iron oxide which has also a number of applications in electronics and spintronics. We 4 compare the thermodynamic stability and electronic structure among the different 5 surfaces terminations. Interestingly, we find that surfaces modified with point defects 6 and adatoms are close in surface energy and in the oxygen-rich and oxygen-poor 7 regimes can be more stable than bulk-like terminations. These surfaces show different 8

SID Symposium Digest of Technical Papers

Organic light‐emitting diodes (OLEDs) are fabricated using a stepwise process, where layers are d... more Organic light‐emitting diodes (OLEDs) are fabricated using a stepwise process, where layers are deposited on top of previous layers. Each of these deposition steps introduces changes to the film structure, both in the crystal structure and in the growth direction. These changes in film structure have dramatic influences on the overall performance of practical devices.