PCSI2017 Session PCSI-ThM: Grande Finale

Spin selection rules govern electronic transport and can therefore be used to identify important transport processes. Electrically detected magnetic resonancd provides an extensive toolbox for this purpose with its recently developed techniques based, e.g., on spin locking and electron double resonance. It is partucularly informative when spin pairs are studied, where the constituents can be easily distinguished spectroscopically.

In this talk, studies of the domnant spin-dependent processes in organic solar cells are summarized using bulk heterojunctions of PCBM and P3HT or PCDTBT. At low temperatures, we identify the recombination of bipolar polaron pairs as the dominant processes and determine the time constants characteristic for this recombination. With increasing temperatures, the negative PCBM polaron becomes invisible. At room temperature, we find the spin-dependent transport in P3HT/PCBM to be governed by a recombination process involving two spin species in P3HT, the positive polaron and a hitherto unreported, possibly defect-related state. We introduce electrically detected magnetic resonance as a method, briefly review its range of applications and discuss the results obtained on our organic devices as a function of temperature and bias voltage.

Sn-containing Si and Ge alloys in an emerging family of semiconductors with the potential to impact group IV materials-based devices. Indeed, the ability to independently engineer both lattice parameter and band gap holds premise to develop enhanced or novel photonic and electronic devices. The ability to incorporate Sn atoms into silicon and germanium at concentrations about one order of magnitude higher than the equilibrium solubility is at the core of these emerging class of semiconductors. Combining the unique properties of SiGeSn with the flexibility in design and fabrication offered by nanowires creates a wealth of opportunities to implement innovative devices. With this perspective, in this presentation we will address the epitaxial growth and stability of these metastable semiconductors with focus on core-shell nanowires. We will discuss their optical and electronic properties based on theoretical and experimental investigation. Strategies to integrate these nanowires in fabrication of optoelectronic devices will also be presented.