TY  - JOUR
A1  - Wolff, Christian Michael
A1  - Caprioglio, Pietro
A1  - Stolterfoht, Martin
A1  - Neher, Dieter
T1  - Nonradiative Recombination in Perovskite Solar Cells
BT  - the Role of Interfaces
JF  - Advanced materials
N2  - Perovskite solar cells combine high carrier mobilities with long carrier lifetimes and high radiative efficiencies. Despite this, full devices suffer from significant nonradiative recombination losses, limiting their V-OC to values well below the Shockley-Queisser limit. Here, recent advances in understanding nonradiative recombination in perovskite solar cells from picoseconds to steady state are presented, with an emphasis on the interfaces between the perovskite absorber and the charge transport layers. Quantification of the quasi-Fermi level splitting in perovskite films with and without attached transport layers allows to identify the origin of nonradiative recombination, and to explain the V-OC of operational devices. These measurements prove that in state-of-the-art solar cells, nonradiative recombination at the interfaces between the perovskite and the transport layers is more important than processes in the bulk or at grain boundaries. Optical pump-probe techniques give complementary access to the interfacial recombination pathways and provide quantitative information on transfer rates and recombination velocities. Promising optimization strategies are also highlighted, in particular in view of the role of energy level alignment and the importance of surface passivation. Recent record perovskite solar cells with low nonradiative losses are presented where interfacial recombination is effectively overcome-paving the way to the thermodynamic efficiency limit.
KW  - interfacial recombination
KW  - open-circuit voltage
KW  - perovskite solar cells
KW  - photoluminescence
Y1  - 2019
U6  - https://doi.org/10.1002/adma.201902762
SN  - 0935-9648
SN  - 1521-4095
VL  - 31
IS  - 52
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Hesse, Julia
A1  - Klier, Dennis Tobias
A1  - Sgarzi, Massimo
A1  - Nsubuga, Anne
A1  - Bauer, Christoph
A1  - Grenzer, Joerg
A1  - Hübner, Rene
A1  - Wislicenus, Marcus
A1  - Joshi, Tanmaya
A1  - Kumke, Michael Uwe
A1  - Stephan, Holger
T1  - Rapid Synthesis of Sub-10nm Hexagonal NaYF4-Based Upconverting Nanoparticles using Therminol((R))66
JF  - ChemistryOpen : including thesis treasury
N2  - We report a simple one-pot method for the rapid preparation of sub-10nm pure hexagonal (-phase) NaYF4-based upconverting nanoparticles (UCNPs). Using Therminol((R))66 as a co-solvent, monodisperse UCNPs could be obtained in unusually short reaction times. By varying the reaction time and reaction temperature, it was possible to control precisely the particle size and crystalline phase of the UCNPs. The upconversion (UC) luminescence properties of the nanocrystals were tuned by varying the concentrations of the dopants (Nd3+ and Yb3+ sensitizer ions and Er3+ activator ions). The size and phase-purity of the as-synthesized core and core-shell nanocrystals were assessed by using complementary transmission electron microscopy, dynamic light scattering, X-ray diffraction, and small-angle X-ray scattering studies. In-depth photophysical evaluation of the UCNPs was pursued by using steady-state and time-resolved luminescence spectroscopy. An enhancement in the UC intensity was observed if the nanocrystals, doped with optimized concentrations of lanthanide sensitizer/activator ions, were further coated with an inert/active shell. This was attributed to the suppression of surface-related luminescence quenching effects.
KW  - core-shell materials
KW  - lanthanides
KW  - nanostructures
KW  - photoluminescence
KW  - upconversion
Y1  - 2018
U6  - https://doi.org/10.1002/open.201700186
SN  - 2191-1363
VL  - 7
IS  - 2
SP  - 159
EP  - 168
PB  - Wiley-VCH
CY  - Weinheim
ER  -