Shaping the nanoworld: From precursors to functional nanocrystals

Shedding Light on Electrochemically Doped Semiconductors: Photochemical Stabilization of the Charge Density in Quantum Dots and Organic Semiconductors

To utilize the full potential of semiconductor materials in device applications including solar cells, LEDs, and lasers, the ability to precisely and controllably tune the charge carrier concentration and hence the doping density is crucial. The conventional methods such as impurity doping with thermal diffusion or ion implantation, have been...

Electrode/electrolyte interfaces in (photo-)electrochemical devices

Climate change, due to the continued emissions of carbon dioxide into our atmosphere and subsequent warming of the planet, is an existential crisis facing humanity. The rising temperature is are resulting in the melting of our ice caps and glaciers, influencing the weather patterns, are making many parts of the world unliveable and are driving...

It's a Trap: Studying the quantum dot surface on an atomistic scale

Due to their size-dependent properties, high photoluminescence quantum yield and relatively cheap solution-based processing, colloidal quantum dots (QDs) are of great interest for application in optoelectronic devices. However, the efficiency of these devices is often limited by the presence of trap states: localized electronic states that lead...

Structural and Excited State Dynamics in Hybrid Halide Perovskites

During the last decade perovskite materials have rapidly emerged, and are currently among the most promising candidates as materials for solar cells and other opto-electronic applications. Although our knowledge related to these materials has advanced rapidly in last few years there are still many unknown aspects and many challenges remain....

Doping on Demand: Permanent electrochemical doping of colloidal quantum dots and organic semiconductors

Control over the charge carrier density of semiconductor materials is essential for various electronic devices. Unfortunately, common electronic doping methods have not always been successful for new generations of semiconductors, such as organic semiconductors and colloidal quantum dots. Therefore, a new doping method that offers a great...

Shedding light on the nanoscale: carrier dynamics and photogeneration in Quantum Dot systems

The generation of excited carrier via light absorption (photogeneration) and their ability to propagate in space in Quantum Dot (QD) films affect critically the performance of QD-based optoelectronic devices. The work performed in this thesis is aimed at increasing the understanding of fundamental processes occurring in QD solutions and QD films...

Light-induced Charge Carrier Dynamics in Metal Halide Perovskites

Metal halide perovskites (MHPs) are interesting candidates for application in photovoltaic devices. During the past decade the efficiency of perovskite solar cells has improved enormously exceeding now values over 24%. In an MHP absorber layer, charge carriers are generated on optical excitation, and decay by band-to-band recombination or by...

Carrier multiplication and cooling in semiconductor quantum dots

In semiconductor quantum dots (QDs), charge carrier cooling is in direct competition with carrier multiplication (CM), a process in which one absorbed photon excites two or more electrons that may improve the light conversion efficiency of photovoltaic devices. CM by an initially hot charge carrier occurs in competition with cooling, with the...

Photoconductivity of Quantum Dot Films Towards Third-Generation Solar Cells

Colloidal semiconductor nanoparticles, also called quantum dots, have unique opto-electronic properties that make them promising candidates for many applications such as solar cells, light–emitting diodes, lasers, or biological imaging. One of the most interesting features is that the bandgap energy can be tuned by changing the particle size....