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ACS Energy Letters

Bernhard M H Weninger, Fokko M Mulder
No abstract text is available yet for this article.
February 8, 2019: ACS Energy Letters
Maryna I Bodnarchuk, Simon C Boehme, Stephanie Ten Brinck, Caterina Bernasconi, Yevhen Shynkarenko, Franziska Krieg, Roland Widmer, Beat Aeschlimann, Detlef Günther, Maksym V Kovalenko, Ivan Infante
Colloidal lead halide perovskite nanocrystals (NCs) have recently emerged as versatile photonic sources. Their processing and luminescent properties are challenged by the lability of their surfaces, i.e., the interface of the NC core and the ligand shell. On the example of CsPbBr3 NCs, we model the nanocrystal surface structure and its effect on the emergence of trap states using density functional theory. We rationalize the typical observation of a degraded luminescence upon aging or the luminescence recovery upon postsynthesis surface treatments...
January 11, 2019: ACS Energy Letters
Andrés F Gualdrón-Reyes, Seog Joon Yoon, Eva M Barea, Said Agouram, Vicente Muñoz-Sanjosé, Ángel M Meléndez, Martha E Niño-Gómez, Iván Mora-Seró
Mixed halide perovskites are one of the promising candidates in developing solar cells and light-emitting diodes (LEDs), among other applications, because of their tunable optical properties. Nonetheless, photoinduced phase segregation, by formation of segregated Br-rich and I-rich domains, limits the overall applicability. We tracked the phase segregation with increasing crystalline size of CsPbBr3- x I x and their photoluminescence under continuous-wave laser irradiation (405 nm, 10 mW cm-2 ) and observed the occurrence of the phase segregation from the threshold size of 46 ± 7 nm...
January 11, 2019: ACS Energy Letters
Mojtaba Abdi-Jalebi, Zahra Andaji-Garmaroudi, Andrew J Pearson, Giorgio Divitini, Stefania Cacovich, Bertrand Philippe, Håkan Rensmo, Caterina Ducati, Richard H Friend, Samuel D Stranks
Halide perovskites passivated with potassium or rubidium show superior photovoltaic device performance compared to unpassivated samples. However, it is unclear which passivation route is more effective for film stability. Here, we directly compare the optoelectronic properties and stability of thin films when passivating triple-cation perovskite films with potassium or rubidium species. The optoelectronic and chemical studies reveal that the alloyed perovskites are tolerant toward higher loadings of potassium than rubidium...
November 9, 2018: ACS Energy Letters
Moritz H Futscher, Akshay Rao, Bruno Ehrler
Singlet fission, an exciton multiplication process in organic semiconductors that converts one singlet exciton into two triplet excitons, is a promising way to reduce thermalization losses in conventional solar cells. One way to harvest triplet excitons is to transfer their energy into quantum dots, which then emit photons into an underlying solar cell. We simulate the performance potential of such a singlet fission photon multiplier combined with a silicon base cell and compare it to a silicon-based tandem solar cell...
October 12, 2018: ACS Energy Letters
Thomas R Hopper, Andrei Gorodetsky, Jarvist M Frost, Christian Müller, Robert Lovrincic, Artem A Bakulin
The rapid relaxation of above-band-gap "hot" carriers (HCs) imposes the key efficiency limit in lead-halide perovskite (LHP) solar cells. Recent studies have indicated that HC cooling in these systems may be sensitive to materials composition, as well as the energy and density of excited states. However, the key parameters underpinning the cooling mechanism are currently under debate. Here we use a sequence of ultrafast optical pulses (visible pump-infrared push-infrared probe) to directly compare the intraband cooling dynamics in five common LHPs: FAPbI3 , FAPbBr3 , MAPbI3 , MAPbBr3 , and CsPbBr3 ...
September 14, 2018: ACS Energy Letters
Eline M Hutter, Tom J Savenije
The relationship between the dipole moment of the methylammonium cation and the optoelectronic properties of lead halide perovskites remains under debate. We show that both the temperature-dependent charge carrier mobility and recombination kinetics are identical for methylammonium and cesium lead iodide, indicating that the role of the monovalent cation is subordinate to the lead iodide framework. From the observation that for both perovskites the electron-hole recombination is thermally activated, we speculate that the bandgap is slightly indirect...
September 14, 2018: ACS Energy Letters
Min Lu, Xiaoyu Zhang, Xue Bai, Hua Wu, Xinyu Shen, Yu Zhang, Wei Zhang, Weitao Zheng, Hongwei Song, William W Yu, Andrey L Rogach
Lead halide perovskite nanocrystals are currently under intense investigation as components of solution-processed light-emitting devices (LEDs). We demonstrate LEDs based on Ag doped-passivated CsPbI3 perovskite nanocrystals with external quantum efficiency of 11.2% and an improved stability. Ag and trilayer MoO3 /Au/MoO3 structure were used as cathode and anode, respectively, which reduce the electron injection barrier and ensure the high transparency and low resistance of the anode. Silver ions diffuse into perovskite film from the Ag electrode, as confirmed by the elemental mapping, the presence of Ag 3d peaks in the X-ray photoelectron spectrum, and the peak shift in the X-ray diffraction patterns of CsPbI3 ...
July 13, 2018: ACS Energy Letters
Yue Zhang, Lu Gao, Emiel J M Hensen, Jan P Hofmann
The evaluation of the stability of emerging earth-abundant metal phosphide electrocatalysts by solely electrochemical current-potential sweeps is often not conclusive. In this study, we investigated Co2 P to evaluate its stability under both acidic (0.5 M H2 SO4 ) and alkaline (1.0 M KOH) hydrogen evolution (HER) conditions. We found that the electrochemical surface area (ECSA) of Co2 P only slightly increased in acidic conditions but almost doubled after electrolysis in alkaline electrolyte. The surface composition of the electrode remained almost unchanged in acid but was significantly altered in alkaline during current-potential sweeps...
June 8, 2018: ACS Energy Letters
Ming Ma, Kai Liu, Jie Shen, Recep Kas, Wilson A Smith
In this work, the highly selective and stable electrocatalytic reduction of CO2 to CO on nanostructured Ag electrocatalysts is presented. The Ag electrocatalysts are synthesized by the electroreduction of Ag2 CO3 formed by in situ anodic-etching of Ag foil in a KHCO3 electrolyte. After 3 min of this etching treatment, the Ag2 CO3 -derived nanostructured Ag electrocatalysts are capable of producing CO with up to 92% Faradaic efficiency at an overpotential as low as 290 mV, which surpasses all of the reported Ag catalysts at identical conditions to date...
June 8, 2018: ACS Energy Letters
Wouter Vijselaar, Roald M Tiggelaar, Han Gardeniers, Jurriaan Huskens
Most photoanodes commonly applied in solar fuel research (e.g., of Fe2 O3 , BiVO4 , TiO2 , or WO3 ) are only active and stable in alkaline electrolytes. Silicon (Si)-based photocathodes on the other hand are mainly studied under acidic conditions due to their instability in alkaline electrolytes. Here, we show that the in-diffusion of nickel into a 3D Si structure, upon thermal annealing, yields a thin (sub-100 nm), defect-free nickel silicide (NiSi) layer. This has allowed us to design and fabricate a Si microwire photocathode with a NiSi interlayer between the catalyst and the Si microwires...
May 11, 2018: ACS Energy Letters
Yuljae Cho, Bo Hou, Jongchul Lim, Sanghyo Lee, Sangyeon Pak, John Hong, Paul Giraud, A-Rang Jang, Young-Woo Lee, Juwon Lee, Jae Eun Jang, Henry J Snaith, Stephen M Morris, Jung Inn Sohn, SeungNam Cha, Jong Min Kim
In a quantum dot solar cell (QDSC) that has an inverted structure, the QD layers form two different junctions between the electron transport layer (ETL) and the other semiconducting QD layer. Recent work on an inverted-structure QDSC has revealed that the junction between the QD layers is the dominant junction, rather than the junction between the ETL and the QD layers, which is in contrast to the conventional wisdom. However, to date, there have been a lack of systematic studies on the role and importance of the QD heterojunction structure on the behavior of the solar cell and the resulting device performance...
April 13, 2018: ACS Energy Letters
Dorottya Hursán, Csaba Janáky
Isotopic labeling experiments were performed to better understand the electrochemical reduction of carbon dioxide on nitrogen-doped porous carbon electrodes. By using nonequilibrated solutions of selectively labeled initial carbon sources (i.e., 13 CO2 and H13 CO3 - ), bicarbonate anion was identified as the predominant source of the carbon monoxide reduction product.
March 9, 2018: ACS Energy Letters
Franziska Krieg, Stefan T Ochsenbein, Sergii Yakunin, Stephanie Ten Brinck, Philipp Aellen, Adrian Süess, Baptiste Clerc, Dominic Guggisberg, Olga Nazarenko, Yevhen Shynkarenko, Sudhir Kumar, Chih-Jen Shih, Ivan Infante, Maksym V Kovalenko
Colloidal lead halide perovskite nanocrystals (NCs) have recently emerged as versatile photonic sources. Their processing and optoelectronic applications are hampered by the loss of colloidal stability and structural integrity due to the facile desorption of surface capping molecules during isolation and purification. To address this issue, herein, we propose a new ligand capping strategy utilizing common and inexpensive long-chain zwitterionic molecules such as 3-( N , N -dimethyloctadecylammonio)propanesulfonate, resulting in much improved chemical durability...
March 9, 2018: ACS Energy Letters
Tanmay Banerjee, Kerstin Gottschling, Gökcen Savasci, Christian Ochsenfeld, Bettina V Lotsch
Covalent organic frameworks (COFs) are a new class of crystalline organic polymers that have garnered significant recent attention as highly promising H2 evolution photocatalysts. This Perspective discusses the advances in this field of energy research while highlighting the underlying peremptory factors for the rational design of readily tunable COF photoabsorber-cocatalyst systems for optimal photocatalytic performance.
February 9, 2018: ACS Energy Letters
David Kiefer, Alexander Giovannitti, Hengda Sun, Till Biskup, Anna Hofmann, Marten Koopmans, Camila Cendra, Stefan Weber, L Jan Anton Koster, Eva Olsson, Jonathan Rivnay, Simone Fabiano, Iain McCulloch, Christian Müller
N-doping of conjugated polymers either requires a high dopant fraction or yields a low electrical conductivity because of their poor compatibility with molecular dopants. We explore n-doping of the polar naphthalenediimide-bithiophene copolymer p(gNDI-gT2) that carries oligoethylene glycol-based side chains and show that the polymer displays superior miscibility with the benzimidazole-dimethylbenzenamine-based n-dopant N-DMBI. The good compatibility of p(gNDI-gT2) and N-DMBI results in a relatively high doping efficiency of 13% for n-dopants, which leads to a high electrical conductivity of more than 10-1 S cm-1 for a dopant concentration of only 10 mol % when measured in an inert atmosphere...
February 9, 2018: ACS Energy Letters
Jarvist Moore Frost, Lucy D Whalley, Aron Walsh
Halide perovskites show unusual thermalization kinetics for above-bandgap photoexcitation. We explain this as a consequence of excess energy being deposited into discrete large polaron states. The crossover between low-fluence and high-fluence "phonon bottleneck" cooling is due to a Mott transition where the polarons overlap ( n ≥ 1018 cm-3 ) and the phonon subpopulations are shared. We calculate the initial rate of cooling (thermalization) from the scattering time in the Fröhlich polaron model to be 78 meV ps-1 for CH3 NH3 PbI3 ...
December 8, 2017: ACS Energy Letters
Francisco Palazon, Carmine Urso, Luca De Trizio, Quinten Akkerman, Sergio Marras, Federico Locardi, Ilaria Nelli, Maurizio Ferretti, Mirko Prato, Liberato Manna
Perovskite-related Cs4 PbBr6 nanocrystals present a "zero-dimensional" crystalline structure where adjacent [PbBr6 ]4- octahedra do not share any corners. We show in this work that these nanocrystals can be converted into "three-dimensional" CsPbBr3 perovskites by extraction of CsBr. This conversion drastically changes the optoelectronic properties of the nanocrystals that become highly photoluminescent. The extraction of CsBr can be achieved either by thermal annealing (physical approach) or by chemical reaction with Prussian Blue (chemical approach)...
October 13, 2017: ACS Energy Letters
Jimin Wang, Mikhail Askerka, Gary W Brudvig, Victor S Batista
Photosystem II (PSII) oxidizes water to produce oxygen through a four-step photocatalytic cycle. Understanding PSII structure-function relations is important for the development of biomimetic photocatalytic systems. The quantum mechanics/molecular mechanics (QM/MM) analysis of substrate water binding to the oxygen-evolving complex (OEC) has suggested a rearrangement of water ligands in a carousel mechanism around a key Mn center. Here, we find that the most recently reported X-ray free-electron laser (XFEL) crystallographic data obtained for the dark-stable S1 state and the doubly flashed S3 state at 2...
October 13, 2017: ACS Energy Letters
Quinten A Akkerman, Daniele Meggiolaro, Zhiya Dang, Filippo De Angelis, Liberato Manna
CsPbI3 nanocrystals are still limited in their use because of their phase instability as they degrade into the yellow nonemitting δ-CsPbI3 phase within a few days. We show that alloyed CsPb x Mn1- x I3 nanocrystals have essentially the same optical features and crystal structure as the parent α-CsPbI3 system, but they are stable in films and in solution for periods over a month. The stabilization stems from a small decrease in the lattice parameters slightly increasing the Goldsmith tolerance factor, combined with an increase in the cohesive energy...
September 8, 2017: ACS Energy Letters
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