A5088089548- Organic Electronics and Photovoltaics
- Conducting polymers and applications
- Organic Light-Emitting Diodes Research
- Molecular Junctions and Nanostructures
- Thin-Film Transistor Technologies
- Organic and Molecular Conductors Research
- Semiconductor materials and devices
- Advanced Chemical Physics Studies
- Fullerene Chemistry and Applications
- Perovskite Materials and Applications
Technische Universität Dresden
2014-2022
A key breakthrough in modern electronics was the introduction of band structure engineering, design almost arbitrary electronic potential structures by alloying different semiconductors to continuously tune gap and band-edge energies. Implementation this approach organic has been hindered strong localization states these materials. We show that influence so far largely ignored long-range Coulomb interactions provides a workaround. Photoelectron spectroscopy confirms ionization energies...
Fermi level control by doping is established since decades in inorganic semiconductors and has been successfully introduced organic semiconductors. Despite its commercial success the multi-billion OLED display business, molecular little understood, with elementary steps controversially discussed mostly-empirical-materials design. Particularly puzzling efficient carrier release, despite a presumably large Coulomb barrier. Here we quantitatively investigate as two-step process, involving...
This work addresses the effect of energy level alignment between hole-transporting material and active layer in vacuum deposited, planar-heterojunction CH3NH3PbIx−3Clx perovskite solar cells. Through a series hole-transport materials, with conductivity values set using controlled p-doping layer, we correlate their ionization potentials open-circuit voltage device. With beyond 5.3 eV, substantial decrease both current density is observed, which highlights delicate energetic balance driving...
Abstract The functionality of organic semiconductor devices crucially depends on molecular energies, namely the ionisation energy and electron affinity. Ionisation affinity values thin films are, however, sensitive to film morphology composition, making their prediction challenging. In a combined experimental simulation study zinc-phthalocyanine its fluorinated derivatives, we show that changes in as function orientation neat or mixing ratio blends are proportional quadrupole component along...
Molecular doping is a key technique for flexible and low‐cost organic complementary semiconductor technologies that requires both efficient stable p‐ n‐type doping. However, in contrast to molecular p‐dopants, highly dopants are commonly sensitive rapid degradation air due their low ionization energies ( IE s) required electron donation, e.g., = 2.4 eV tetrakis(1,3,4,6,7,8‐hexahydro‐ 2H ‐pyrimido[1,2‐ ]pyrimidinato)ditungsten(II) (W 2 (hpp) 4 ). Here, the stability of various host:W...
Efficient n-doping of organic semiconductors requires electron-donating molecules with small ionization energies, making such n-dopants usually sensitive to degradation under air exposure. A workaround consists in the usage air-stable precursor containing actual species. Here, we systematically analyze doping mechanism small-molecule o-MeO-DMBI-Cl, which releases a highly reducing o-MeO-DMBI radical upon thermal evaporation. n-Doping N,N-bis(fluoren-2-yl)-naphthalene tetracarboxylic diimide...
Charge carrier transport is a key parameter determining the efficiency of organic solar cells, and closely related to density free trapped states. For trap characterization, impedance spectroscopy suitable, non-invasive method, applicable complete semiconductor devices. In order contribute capacitive signal, traps must be filled with charge carriers. Typically, filling achieved by illuminating device or injecting carriers through application forward bias voltage. However, in both cases,...
Abstract Organic photovoltaics (PV) is an energy-harvesting technology that offers many advantages, such as flexibility, low weight and cost, well environmentally benign materials manufacturing techniques. Despite growth of power conversion efficiencies to around 19 % in the last years, organic PVs still lag behind inorganic PV technologies, mainly due high losses open-circuit voltage. Understanding improving open circuit voltage solar cells challenging, it controlled by properties a...
Abstract In modern electronics, it is essential to adapt band structures by adjusting energy levels and gaps. At first sight, this “band structure engineering” seems impossible in organic semiconductors, which usually exhibit localized electronic states instead of Bloch bands. However, the strong Coulomb interaction semiconductors allows for a continuous shift ionization (IE) over wide range mixing molecules with halogenated derivatives that different quadrupole moments. Here, effect level...
We investigate the influence of built-in voltage on performance organic bulk heterojuction solar cells that are based a p-i-n structure. Electrical doping in hole and electron transport layer allows to tune their work function hence adjust voltage: Changing concentration from 0.5 32 wt% induces shift towards levels increases voltage. To determine voltage, we use electroabsorption spectroscopy which is an evaluation spectra caused by change absorption due electric field (Stark effect). For...
The air sensitivity of n-doped layers is crucial for the long-term stability organic electronic devices. Although several air-stable and highly efficient n-dopants have been developed, reason varying between different layers, in which n-dopant molecules are dispersed, not fully understood. In contrast to previous studies that compared doped films with energy levels neat host or dopant we trace back degree integer charge transfer states (ICTCs) formed by anions cations. Our data indicate a...
In modern electronics, it is essential to create almost arbitrary band structures by adjusting the energy bands and gap. Until now, structure engineering in organic semiconductors has not been possible, since they usually exhibit localized electronic states instead of bands. a recent publication [1], we showed that possible continuously shift ionization (IE) over wide range mixing them with halogenated derivatives. This tuning mechanism based on interactions excess charges mean quadrupole...