Free Charge Carrier Generation by Visible-Light-Absorbing Organic Spacers in Ruddlesden-Popper Layered Perovskites.

Incorporating organic semiconductor building blocks as spacer cations into layered hybrid perovskites provides an opportunity to develop new materials with novel optoelectronic properties, including nanoheterojunctions that afford spatial separation of electron and hole transport. However, identifying organics with suitable structure and electronic energy levels to selectively absorb visible light has been a challenge in the field. In this work, we introduce a new lead-halide-based Ruddlesden-Popper perovskite structure based on a visible-light-absorbing naphthalene-iminoimide cation (NDI-DAE).

Excited-State Dynamics of MAPbBr: Coexistence of Excitons and Free Charge Carriers at Ultrafast Times.

Methylammonium lead tribromide perovskite (MAPbBr) is an important material, for example, for light-emitting applications and tandem solar cells. The relevant photophysical properties are governed by a plethora of phenomena resulting from the complex and relatively poorly understood interplay of excitons and free charge carriers in the excited state. In this study, we combine transient spectroscopies in the visible and terahertz range to investigate the presence and evolution of excitons and free charge carriers at ultrafast times upon excitation at various photon energies and densities.

Electrochemical Doping in Ordered and Disordered Domains of Organic Mixed Ionic-Electronic Conductors.

Conjugated polymers are increasingly used as organic mixed ionic-electronic conductors in electrochemical applications for neuromorphic computing, bioelectronics, and energy harvesting. The design of efficient electrochemical devices relies on large modulations of the polymer conductivity, fast doping/dedoping kinetics, and high ionic uptake. In this work, structure-property relations are established and control of these parameters by the co-existence of order and disorder in the phase morphology is demonstrated.

Correction: Bipolarons rule the short-range terahertz conductivity in electrochemically doped P3HT.

Correction for 'Bipolarons rule the short-range terahertz conductivity in electrochemically doped P3HT' by Demetra Tsokkou , , 2022, DOI: 10.1039/d1mh01343b.

Bipolarons rule the short-range terahertz conductivity in electrochemically doped P3HT.

Doping of organic semiconductor films enhances their conductivity for applications in organic electronics, thermoelectrics and bioelectronics. However, much remains to be learnt about the properties of the conductive charges in order to optimize the design of the materials. Electrochemical doping is not only the fundamental mechanism in organic electrochemical transistors (OECTs), used in biomedical sensors, but it also represents an ideal playground for fundamental studies.

Ultrafast Charge Transfer Dynamics at the Origin of Photoconductivity in Doped Organic Solids.

In spite of their growing importance for optoelectronic devices, the fundamental properties and photophysics of molecularly doped organic solids remain poorly understood. Such doping typically leads to a small fraction of free conductive charges, with most electronic carriers remaining Coulombically bound to the ionized dopant. Recently, we have reported photocurrent for devices containing vacuum-deposited TAPC (1,1-bis(4-bis(4-methylphenyl)aminophenyl)cyclohexane) doped with MoO, showing that photoexcitation of charged TAPC molecules increases the concentration of free holes that contribute to conduction.

Polaron Photoconductivity in the Weak and Strong Light-Matter Coupling Regime.

We investigate the potential for cavity-modified electron transfer in a doped organic semiconductor through the photocurrent that arises from exciting charged molecules (polarons). When the polaron optical transition is strongly coupled to a Fabry-Perot microcavity mode, we observe polaron polaritons in the photoconductivity action spectrum and find that their magnitude depends differently on applied electric field than photocurrent originating from the excitation of uncoupled polarons in the same cavity. Crucially, moving from positive to negative detuning causes the upper and lower polariton photocurrents to swap their field dependence, with the more polaronlike branch resembling that of an uncoupled excitation.

Comparing the excited-state properties of a mixed-cation-mixed-halide perovskite to methylammonium lead iodide.

Organic-inorganic perovskites are one of the most promising photovoltaic materials for the design of next generation solar cells. The lead-based perovskite prepared with methylammonium and iodide was the first in demonstrating high power conversion efficiency, and it remains one of the most used materials today. However, perovskites prepared by mixing several halides and several cations systematically yield higher efficiencies than "pure" methylammonium lead iodide (MAPbI) devices.

Tetraphenylhexaazaanthracenes: 16π Weakly Antiaromatic Species with Singlet Ground States.

Tetraphenylhexaazaanthracene, TPHA-1, is a fluorescent zwitterionic biscyanine with a closed-shell singlet ground state. TPHA-1 overcomes its weak 16π antiaromaticity by partitioning its π system into 6π positive and 10π negative cyanines. The synthesis of TPHA-1 is low yielding and accompanied by two analogous TPHA isomers: the deep red, non-charge-separated, quinoidal TPHA-2, and the deep green TPHA-3 that partitions into two equal but oppositely charged 8π cyanines.

Tin Oxide Nanowires: The Influence of Trap States on Ultrafast Carrier Relaxation.

We have studied the optical properties and carrier dynamics in SnO(2) nanowires (NWs) with an average radius of 50 nm that were grown via the vapor-liquid solid method. Transient differential absorption measurements have been employed to investigate the ultrafast relaxation dynamics of photogenerated carriers in the SnO(2) NWs. Steady state transmission measurements revealed that the band gap of these NWs is 3.

Low Temperature Growth of In2O3and InN Nanocrystals on Si(111) via Chemical Vapour Deposition Based on the Sublimation of NH4Cl in In.

Indium oxide (In2O3) nanocrystals (NCs) have been obtained via atmospheric pressure, chemical vapour deposition (APCVD) on Si(111) via the direct oxidation of In with Ar:10% O2at 1000 °C but also at temperatures as low as 500 °C by the sublimation of ammonium chloride (NH4Cl) which is incorporated into the In under a gas flow of nitrogen (N2). Similarly InN NCs have also been obtained using sublimation of NH4Cl in a gas flow of NH3. During oxidation of In under a flow of O2the transfer of In into the gas stream is inhibited by the formation of In2O3around the In powder which breaks up only at high temperatures, i.

Femtosecond Carrier Dynamics in In(2)O(3) Nanocrystals.

We have studied carrier dynamics in In(2)O(3) nanocrystals grown on a quartz substrate using chemical vapor deposition. Transient differential absorption measurements have been employed to investigate the relaxation dynamics of photo-generated carriers in In(2)O(3) nanocrystals. Intensity measurements reveal that Auger recombination plays a crucial role in the carrier dynamics for the carrier densities investigated in this study.