Photoinduced p- to n-type Switching in Thermoelectric Polymer-Carbon Nanotube Composites

Dörling, Bernhard et al.UV-induced switching from p- to n-type character is demonstrated during deposition of carbon-nanotube–conjugated polymer composites. This opens the possibility to photopattern n-type regions within an otherwise p-type film, which has a potential for complementary circuitry or, as shown here, thermoelectric generators made from a single solution.The authors would like to thank Dr. Isabel Alonso (ICMAB) and Prof. Salvador Ferrer (ALBA) for assisting during the synchrotron sessions as well as for useful discussions. The authors would also like to acknowledge financial support from the Ministerio de Economía y Competitividad of Spain through projects CSD2010–00044 (Consolider NANOTHERM) and MAT2012–37776 and the European Research Council (ERC) under grant agreement nos. 637624 and 648901. C.M. gratefully acknowledges fi nancial support from Formas, the Knut and Alice Wallenberg Foundation through a Wallenberg Academy Fellowship. The transmission X-ray microscopy experiments were performed at MISTRAL beamline at ALBA Synchrotron with the collaboration of ALBA staff. A.E.B. thanks the Egyptian Ministry of Higher Education for funding through the Short-term Scientifi c Mission Postdoctoral program. The authors thank Dr. Elena Bailo (Witec) for assistance with the Raman imaging experiments.Peer reviewe

Density control on self-assembling of Ge islands using carbon-alloyed strained SiGe layers

The authors show that by deposition of 0.1 ML of carbon prior to the self-assembledgrowth of Gequantum dots on a strained Si1−xGexbuffer layer a striking decrease in dot density by two orders of magnitude from about 1011to109cm−2 occurs when the Ge content of the buffer layer increases from 0% to 64%. Their results give experimental evidence for a kinetically limited growth mechanism in which Ge adatom mobility is determined by chemical interactions among C, Si, and Ge. Thus, by adjusting the Ge content of the SiGe buffer layer onto which a carbonsubmonolayer is deposited they are able to fine tune the density of the carbon-induced Gequantum dots

Optical properties of semiconductors

In this chapter we present basic concepts which are relevant to link the results obtained from ellipsometry data analysis with fundamental properties of semiconductors for photovoltaic applications. The linear optical properties of semiconductors are best discussed in terms of the relationship between the dielectric function ε and the band structure.The authors thank the Spanish Ministry of Economy and Competitiveness (MINECO) for funding through grants CSD2010-00044, MAT2015-70850-P, and the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV- 2015-0496).Peer reviewe

Continuous lateral gradients in film morphology for position sensitive detection and organic solar cell optimization

We present a method to fabricate binary organic donor and acceptor blends exhibiting a controlled lateral gradient in morphology. Upon combining photometry, ellipsometry and Xray maps together with photoinduced absorption measurements, we show how the gradual exposure to solvent vapor results in a varying degree of polymer crystallinity for the polythiophene/soluble fullerene system along one direction. These morphologically graded samples are characterized by a spectral photoresponse that depends on the specific location in the area of the device where the light beam impinges, a property that stands as proof-of-concept for position sensitive detection. Moreover, we demonstrate that the development of graded morphologies is an effective one-step method which allows for fast performance optimization of organic solar cells. Finally, the appropriateness of eight different solvents for morphology control via vapor annealing is evaluated in a time-effective way using the advanced method, which helps to identify boiling point and solubility as the key processing parameters.The authors thank the Spanish Ministerio de Economía y Competitividad for funding through the projects MAT2009- 10642, PLE2009-0086, MAT2012-37776, and TEC2010- 21830-C02-02 as well as Ramon y Cajal contract number RYC-2009-05475. We are indebted to Ignasi Burgués (ICMAB) for assistance with evaporation and encapsulation, to Anna Crespi (ICMAB) for assistance with the X-ray measurements, to Dmitri Nassyrov (ICMAB) for his help at the early stages of this project, and to M.I. Alonso and A. Goñi (ICMAB) for fruitful discussions. We also acknowledge PCT patent with application number PCT/ES2011/070841 and publication reference WO/2012/076740.Peer reviewe

Advanced Optical Characterization of PEDOT:PSS by Combining Spectroscopic Ellipsometry and Raman Scattering

The optical properties of various PEDOT:PSS films obtained by drop casting and blade coating are analyzed by variable-angle spectroscopic ellipsometry in the visible-UV spectral range. We discuss observed differences in the optical spectra due to PSS content and DMSO treatment and correlate them to structural changes extracted from Raman measurements. In particular, we investigate the optical anisotropy of the complex refractive indices which arises from the in-plane arrangement of the PEDOT backbones, giving rise to optically uniaxial behavior with the optic axis perpendicular to the film plane. Although this is widely accepted, most investigations disregard the anisotropy for simplicity, which sometimes leads to inaccurate conclusions. In this work, we compare the results of isotropic and anisotropic analyses to clarify which kind of errors we can expect if anisotropy is not considered. Finally, the correlation between Raman scattering and ellipsometric analyses shows that not only local structural changes of the chain conformation but also the overall morphology of the composite films are significant in the interpretation of Raman spectra.The authors acknowledge funding from the Spanish Ministerio de Ciencia e Innovación (MICINN) through grants PID2019-106860GB-I00 and PID2020-119777GB-I00 and the Spanish Severo Ochoa Centre of Excellence program CEX2019-000917-S, as well as AGAUR, Generalitat de Catalunya, grant 2017-SGR-00488. M.K. is grateful to the UAB PhD program in Materials Science in which she is enrolled and the China Scholarship Council for funding (CSC 201809370071). We thank Agustín Mihi and Mariano Campoy-Quiles for their constant support and ideas.With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe

High-throughput evaluation and hyperspectral imaging of ternary organic solar cells. Dataset

The dataset here provided corresponds to the open access article with DOI 10.1002/aenm.201902417. The package contains the raw data (Raman spectra, photocurrent, photoluminescence, reflectivity) extracted from ternary organic solar cells processed following combinatorial schemes. The datasets used to build the figures of the main article are included as well to reproduce the depicted illustrations.The dataset is divided into two main folders. The "Raw data" folder contains the raw Raman, photoluminescence, absorption, reflectivity and photocurrent hyperspectral imaging data took in ternary organic solar cells. The "Figures" folder contains the data points required to reproduce the figures of the main manuscript (including the Supplementary Information).Peer reviewe

Energy-dependent dielectric tensor axes in monoclinic -3,4,9,10-perylene tetracarboxylic dianhydride

We have determined the complex dielectric tensor of single crystalline 3,4,9,10-perylene tetracarboxylic dianhydride (-PTCDA) as a function of energy in the range between 1.4 and 5.0 eV. The results obtained reflect the monoclinic symmetry of the crystal: The principal axes of the real and the imaginary part of the tensor in general do not coincide and show chromatic dispersion. Monoclinic behavior allows rotation of the components and in the plane perpendicular to the unique symmetry axis . The experimental results indicate that the energies of the optical transitions observed in the weak component coincide with energies in which a resonance effect due to coupling with the stronger component occurs. These resonances appear at energies close to electronic excitations such as the optical gap, the transport gap and the highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) peak-to-peak gap and their assignments are discussed based on theoretical calculationsWe dedicate this paper to the memory of Norbert Karl and Manuel Cardona who encouraged this work in its beginnings. MIA and MG acknowledge funding by the Spanish Ministerio de Ciencia e Innovación (MICINN) through grants PID2019-106860GB-I00 (highN) and CEX2019-000917-S (FUNFUTURE, in the framework of the Spanish Severo Ochoa Centre of Excellence program), as well as AGAUR, Spain for grant 2017-SGR-00488. FS and RS wish to acknowledge financial support from the DFG, Germany .With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe

Dataset: The photocurrent-composition dependence of binary bulk heterojunction organic solar cells-combining high throughput experimentation and artificial intelligence models

This dataset corresponds to the article: "Predicting the photocurrent-composition dependence in organic solar cells" Xabier Rodríguez-Martínez, Enrique Pascual-San-José, Zhuping Fei, Martin Heeney, Roger Guimerà and Mariano Campoy-Quiles The article was first published on 07 Jan 2021 Energy Environ. Sci., 2021 DOI: 10.1039/D0EE02958K The dataset is divided into five main folders, which are briefly described below. - The "Descriptors" folder contains the detailed lists of optoelectronic descriptors used for the different training procedures performed throughout the work, i.e., a random selection of parameters, a hand-picked selection of parameters and a median of their corresponding distributions. The database of HOMO/LUMO levels and mobilities as retrieved from literature is included as well in an Excel spreadsheet. - The "Discrete devices" folder contains the photovoltaic figures-of-merit (open-circuit voltage, short-circuit current density, fill factor and power conversion efficiency) of the devices prepared at controlled donor:acceptor ratios. In these samples, the active layer thickness was screened in a high-throughput fashion using lateral gradients. Therefore, the variations observed at a given donor:acceptor ratio are solely due to the change in active layer thickness. - The "Graded devices" folder contains Raman mapping and Light-Beam Induced Current (LBIC) data for the 2D combinatorial devices, i.e. those including and orthogonal arrangement of active layer thickness and donor:acceptor ratio gradients on a single large area substrate. - The "Figures" folder contains a Jupyter Notebook file and, alternatively, a Python script, whose full execution in a row generates the figures of the main text and its Electronic Supplementary Information. These codes are designed to run with Python 3.7.3 and Scikit-Learn v0.22.2, while accessing data from other main folders (including "Descriptors", "Discrete devices" and "Graded devices") and subfolders ("Pools" and "Supplementary data"). For this reason, either code must be executed right from their original location within the "Figures" folder while keeping the original folder labels as well. - Finally, the "Raw data" folder contains the binary files generated as per the optoelectronic characterization of the 2D combinatorial devices. These were extracted employing our WITec alpha 300 RA+ confocal Raman setup in combination with LBIC and White-Beam Induced Current (WhiteBIC) measurements. We include as well scripts compatible with GNU Octave (*.m) to display the raw data.This dataset corresponds to the open-source article with DOI 10.1039/D0EE02958K. The package contains (i) the detailed lists of optoelectronic descriptors used to feed machine-learning algorithms; (ii) the photovoltaic figures-of-merit of the organic solar cells therein fabricated; (iii) the photocurrent-composition dependence obtained in 15 different donor:acceptor organic photovoltaic blends using high-throughput combinatorial experimentation; (iv) a set of Python scripts to reproduce the figures of the main text of the article and its supplementary information; and (v) the raw data as extracted from confocal Raman imaging and photocurrent mapping.The dataset is divided into five main folders, which are briefly described in the following lines. The "Descriptors" folder contains the detailed lists of optoelectronic descriptors used for the different training procedures performed throughout the work. The "Discrete devices" folder contains the photovoltaic figures-of-merit (open-circuit voltage, short-circuit current density, fill factor and power conversion efficiency) of the devices prepared at controlled donor:acceptor ratios. The "Graded devices" folder contains Raman mapping and Light-Beam Induced Current (LBIC) data for the 2D combinatorial devices. The "Figures" folder contains a Jupyter Notebook file and, alternatively, a Python script, whose full execution in a row generates the figures of the main text and its supplementary information. Finally, the "Raw data" folder contains the binary files generated as per the optoelectronic characterization of the 2D combinatorial devices.Peer reviewe