1. Topics ACOPhys “Opening Week” Get-together by examples 1.) Organic Optoelectronics 2.) Electronic Structure of Organic Materials 3.) Plastic Solar Cell 4.) Random Matrix Theory and Excitons in Disordered Quantum Wells Planning next steps

2. Get-together by means of examples: Discussing Quantum Wells and Wires Prof. Gerhard Gobsch, “Applied Physics” Prof. Erich Runge, “Computational Physics” Technical University of Ilmenau, Institute of Physics

3. Semiconductors : An energy gap separates states of mobile electrons from states of mobile holes in the so-called valence band, which is otherwise occupied by electrons. What happens if electrons and holes meet ? What happens at the interface of two semiconductors ? Energy Position

4. Light Emitting Diodes (LED) + Semiconductor quantum well lasers... and the hairy details as presented by the world‘s best-known expert The simple view of a theoretical physicist... Energy Position Nobel prize 2000: Kroemer und Alferov

5. http://britneyspears.ac/physics/fplasers/images/dhlaser.jpg Light Emitting Diodes (LED) + Semiconductor quantum well lasers... and the hairy details as presented by the world‘s best-known expert

6. The Gallium Nitride Revolution: LEDs and lasers based on InGaN / GaN quantum wells Does the revolution eat its children? ‘‘Long reign the OLED’’

7. Band gaps of hexagonal nitride compounds

8. What about Quantum Mechanics ?

9. http://www.almaden.ibm.com/ almaden/media/image_mirage.html Electrons show wave-like properties,...... some of them are easily explained...... and some are a bit harder to get used to... Energy Position What about Quantum Mechanics ?

10. 0 1 eV 2 eV 3 eV 4 eV Infra redUltraviolet CdSe nano spheres covered with ZnSe act as quantum dots http://www.evidenttech.com/products/core_shell_evidots/overview.php 2 nm: Lake Placid Blue5 nm: Maple-Red Orange conf h  2m L E 2 ~ ~ 2 2 Confinement energy... some of them are easily explained...

11. Excitons Enhanced particle-particle interaction: e-h bound state... some of them are easily explained... 100 meV 2-20 nm 1.5 eV E B = 5 meV

12. Computation of quantum wire excitons

13. Disorder-free structures, exciton parameters Dispersion of multi-subband QWR excitons low-energy states of 10 7 X 10 7 matrix electron-hole correlation decomposition into valence-band orbitals dispersion relation and exciton mass M X spin-splitting, polarization anisotropy A. Siarkos, E. Runge, PRB 61, 16854 (2000)

14. Spatially resolved spectroscopy K. Matsuda et al., PRL 91, 177401 (2003): 30 nm resolution, wavefunction mapping but: Ch. Lienau, E. Runge, Physik Journal, Jan. 2004 and to be published