Effect of spin–phonon interactions on Urbach tails in flexible [M2(bdc)2(dabco)]

The optical properties of MOFs [M2(bdc)2(dabco)] (M = Co, Ni, Cu, Zn) in the wavelength region of 300–1000 nm were studied, the electronic band-to-band transitions were determined and characterized by the Kubelka–Munk approach and DFT calculations.

New Research in Solar Cells: Urbach Tails and Open Circuit Voltage

<div class="page" title="Page 45"><div class="layoutArea"><div class="column"><p>The development of various emerging photovoltaic technologies, as classified by the National Renewable Energy Laboratory, has experienced very different rates of progress over the last five to ten years. In particular, two thin-film technologies, quantum dot solar cells and perovskite-based solar cells, have achieved drastically different values for power conversion efficiency as quantum dots have failed to keep up with perovskites. Clearly, the materials are very different, but in order to quantify the discrepancy in efficiency, we focus on measuring the tail of the absorption past the nominal band edge and therefore the Urbach energy of the two materials. We discuss a theoretical relationship between Urbach energy and open circuit voltage based on the original considerations by Shockley and Queisser on the efficiency limits of solar cells.</p></div></div></div>

Optical Dispersion Characterization of Sprayed Zn1-xMnxO Thin Films

Uniform and adherent Zn1-xMnxO films have been deposited by using spray pyrolysis technique on glass substrates. The optical properties and dispersion parameters of zinc oxide have been studied as a function of doping concentration with Mn. Changes in direct optical energy band gap of cobalt oxide films were confirmed after doping, the optical energy gap Eg increased from 3.13 eV for the undoped ZnO to 3.39 eV with increasing the doping concentration of Mn to 4%. The changes in dispersion parameters and Urbach tails were investigated. An increase in the doping concentration causes a decrease in the average oscillator strength. The single-oscillator parameter has been reported.