Bertrand J Tremolet de Villers

• Researcher at National Renewable Energy Laboratory

Laser ablation is a scalable technique for decreasing the effective tortuosity of electrodes by selectively removing material with high precision. Applied to ≈ 110μm thick electrode coatings, this work focuses on understanding the impact of laser ablation on electrode material properties at the beginning of life and synergistic impacts of ablated c...

Due to inherent properties of the silicon (Si)-electrolyte interphase (SEI)—complexity, high reactivity and continuous evolution—it remains a poorly understood topic in advanced Si-based Li-ion battery (LiB) research, 1,2 and its detailed and real-time analysis is a great challenge. Vibrational spectroscopy, such as Raman and Fourier-transform infr...

Next-generation electrodes for rechargeable lithium-ion batteries (LiBs) promise higher energy and power storage at lower cost. For example, silicon has a theoretical capacity approximately 10 times higher compared to current state-of-the-art anodes based on graphite, 3580 mAhg ⁻¹ vs 372 mAhg ⁻¹ , respectively. ¹ On the other side of the cell, it h...

We present a study of the lithium nickel manganese cobalt oxide (LiNi0.6Mn0.2Co0.2O2, NMC622) cathode‐electrolyte interphase (CEI) during galvanostatic charging and discharging using in situ attenuated total reflectance Fourier transform infrared (ATR‐FTIR) methods to investigate the voltage dependent electrolyte solution structure changes at the i...

Acetogenic bacteria represent a class of organisms capable of converting reducing equivalents and carbon dioxide into products with carbon-carbon bonds. Materials-based bio-electrochemical approaches are attractive for supplying biological organisms directly with grid-supplied electrons to convert carbon dioxide to value-added chemicals. Carbon nan...

Silicon (Si) is a promising anode material for high-energy-density lithium-ion batteries (LIBs), but its short calendar life and poor cycling performance prevent its large-scale adoption. Introducing magnesium (Mg) salt into the electrolyte has been recently shown to form a ternary Li-Mg-Si Zintl phase upon lithiation of Si and improve the cycling...

In the last decade, cathodes based on lithium nickel manganese cobalt oxide, LiNi 1-x-y Mn x Co y O 2 , have garnered much attention due to their high theoretical capacity, up to 280mAhg ⁻¹ . ¹ In general, increasing the Ni content in these materials boosts the capacity, however this usually comes at the cost of decreased stability. ² Thus, stabili...

Silicon (Si) is a promising anode material for high energy density lithium-ion batteries (LIBs) but its poor cycling performance prevents its large-scale adoption. Introducing Mg salt into the electrolyte has shown to form a ternary Li-Mg-Si Zintl phase upon lithiation of Si and improve the cycling stability; however, its formation mechanism and im...

A trace amount of water in an electrolyte is one of the factors detrimental to the electrochemical performance of silicon (Si)-based lithium-ion batteries that adversely affect the formation and evolution of the solid electrolyte interphase (SEI) on Si-based anodes and change its properties. Thus far, a lack of fundamental and mechanistic understan...

Layered P2‐type Na0.8Mn0.5Fe0.5O2 cathode material is a promising candidate for next‐generation sodium‐ion batteries due to the economical and environmentally benign characteristics of Mn and Fe. The poor cycling stability of the material, however, is still a problem that must be solved. To address the problem, electrochemically inactive Mg²⁺ was i...

We present a novel spectroscopic technique for in-situ Raman microscopy studies of battery electrodes. By creating nanostructures on a copper mesh current collector, we were able to utilize surface-enhanced Raman spectroscopy (SERS) to monitor the evolution of the silicon anode-electrolyte interphase (SiEI). The spectra show reversible Si peak inte...

High efficiency organic photovoltaic devices have relied on the development of new donor and acceptor materials to optimize opto-electronic properties, promote free carrier generation, and suppress recombination losses. With single junction efficiencies exceeding 15%, materials development must now target long-term stability. This work focuses on t...

Long-term device stability is the most pressing issue that impedes perovskite solar cell commercialization, given the achieved 22.7% efficiency. The perovskite absorber material itself has been heavily scrutinized for being prone to degradation by water, oxygen and ultraviolet light. To date, most reports characterize device stability in the absenc...

To push perovskite solar cell (PSC) technology toward practical applications, large-area perovskite solar modules with multiple sub-cells need to be developed by fully scalable deposition approaches. Here, we demonstrate a deposition scheme for perovskite module fabrication with spray coating of a TiO2 electron transport layer (ETL) and blade coati...

The interfacial microstructure in organic bulk heterojunction solar cells can dictate photovoltaic performance. By controlling the chemical interactions of bulk heterojunction components with specific surfaces, the electrical pathways at interfaces can be precisely varied to achieve suitable electronic properties across such interfaces. This is stu...

We investigated and characterized the stability of the power output from methylammonium lead iodide perovskite photovoltaic devices produced with various hole-collecting anode configurations consisting of Au, Ag, MoOx/Au, MoOx/Ag, and MoOx/Al. The unencapsulated devices were operated under constant illumination and constant load conditions in labor...

Solvent additives such as diiodooctane (DIO) are becoming ubiquitous in processing high performance organic photovoltaic (OPV) active layers. Here, we investigate the effects of DIO on the long-term stability of the active layer by studying the photodegradation under ambient white light illumination of the polymer PTB7-Th in pure polymer thin films...

Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is less selective for holes in an inverted-architecture organic photovoltaic (OPV) than it is in a conventional-architecture OPV device due to differences between the interfacial-PSS concentration at the top and bottom of the PEDOT:PSS layer. In this work, thin layers of polysulfo...

The role of the interface between an MoOx anode interlayer and polymer:fullerene bulk heterojunction is investigated. Processing differences in the MoOx induce large variations in the vertical stratification of the bulk heterojunction films. These variations are found to be inconsistent in predicting device performance, with a much better gauge bei...

A high-yielding synthesis of a series of polyimide dendrimers, including decacyclene- and perylene-containing dendrimer D6, in which two types of polyimide dyes are present, is reported. In these constructs, the branching unit is represented by trisphenylamine, and the solubilizing chains by N-9-heptadecanyl-substituted perylene diimides. The photo...

A high-yielding synthesis of a series of polyimide dendrimers, including decacyclene- and perylene-containing dendrimer D6, in which two types of polyimide dyes are present, is reported. In these constructs, the branching unit is represented by trisphenylamine, and the solubilizing chains by N-9-heptadecanyl-substituted perylene diimides. The photo...

We report on investigations of the stability of inverted organic solar cells with ZnO electron collecting interlayer that are solution-processed from zinc acetate (ZnAc) or diethylzinc (deZn) precursors. Characterization of the respective solar cells suggests that the two materials initially function similarly in devices, however, we find that devi...

Dithienogermole-co-thieno[3,4-c]pyrroledione (DTG-TPD) polymers incorporating chemically cross-linkable sidechains are reported and their properties compared to a parent polymer with simple octyl sidechains. Two cross-linking groups and mechanisms are investigated, UV-promoted radical cross-linking of an alkyl bromide cross-linker and acid-promoted...

It is demonstrated that a combination of microsecond transient photocurrent measurements and film morphology characterization can be used to identify a charge-carrier blocking layer within polymer:fullerene bulk-heterojunction solar cells. Solution-processed molybdenum oxide (s-MoOx) interlayers are used to control the morphology of the bulk-hetero...

A novel n-type material, an alkylated decacyclene triimide (DTI), is utilized in organic photovoltaic devices as the first non-fullerene acceptor that performs efficiently with the benchmark donor polymer poly(3-hexylthiophene) (P3HT) as well as various narrow band gap polymers.

We examine the ultrafast dynamics of exciton migration and polaron production in sequentially processed ‘quasi-bilayer’ and preblended ‘bulk heterojunction’ (BHJ) solar cells based on conjugated polymer films that contain the same total amount of fullerene. We find that even though the polaron yields are similar, the dynamics of polaron production...

To understand the effects of Ag nanoparticles (NPs) on the performance of organic solar cells, we examined the properties of hybrid poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric-acid-methyl-ester:Ag NP solar cells using photoinduced charge extraction with a linearly increasing voltage. We find that the addition of Ag NPs into the active layer sig...

Light conversion and carrier transport in hybrid solar cells fabricated by spin coating poly(3-hexylthiophene) (P3HT) on ordered n-GaAs nanopillars are studied via electrical and optical characterization. The performance of hybrid nanopillar/P3HT solar cells is compared to control cells having either only P3HT or only GaAs nanopilllars. The hybrid...

In this work, we study hybrid solar cells based on poly(3-hexylthiophene)-coated GaAs nanopillars grown on a patterned GaAs substrate using selective-area metal organic chemical vapor deposition. The hybrid solar cells show extremely low leakage currents (I ≅ 45 nA @−1V) under dark conditions and an open circuit voltage, short circuit current densi...

Plastic photovoltaic devices offer a real potential for making solar energy economically viable. Unfortunately, bulk heterojunction (BHJ) solar cells fabricated from blends of the commonly used materials poly(3-hexylthiophene), P3HT, and phenyl-C61-butyric acid methyl ester, PCBM, sometimes exhibit low efficiencies even when the procedures followed...

The authors investigate how the use of different metal electrodes affects the ability of poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) films to undergo amplified spontaneous emission (ASE). High-work-function metals such as Ag or Au have little effect on the ASE threshold, but low-work-function metals such as Ca or Al compl...