TY  - JOUR
A1  - Kraus, Hannes
A1  - Heiber, Michael C.
A1  - Väth, Stefan
A1  - Kern, Julia
A1  - Deibel, Carsten
A1  - Sperlich, Andreas
A1  - Dyakonov, Vladimir
T1  - Analysis of Triplet Exciton Loss Pathways in PTB7:PC\(_{71}\)BM Bulk Heterojunction Solar Cells
JF  - Scientific Reports
N2  - A strategy for increasing the conversion efficiency of organic photovoltaics has been to increase the VOC by tuning the energy levels of donor and acceptor components. However, this opens up a new loss pathway from an interfacial charge transfer state to a triplet exciton (TE) state called electron back transfer (EBT), which is detrimental to device performance. To test this hypothesis, we study triplet formation in the high performing PTB7:PC\(_{71}\)BM blend system and determine the impact of the morphology-optimizing additive 1,8-diiodoctane (DIO). Using photoluminescence and spin-sensitive optically detected magnetic resonance (ODMR) measurements at low temperature, we find that TEs form on PC\(_{71}\)BM via intersystem crossing from singlet excitons and on PTB7 via EBT mechanism. For DIO blends with smaller fullerene domains, an increased density of PTB7 TEs is observed. The EBT process is found to be significant only at very low temperature. At 300 K, no triplets are detected via ODMR, and electrically detected magnetic resonance on optimized solar cells indicates that TEs are only present on the fullerenes. We conclude that in PTB7:PC\(_{71}\)BM devices, TE formation via EBT is impacted by fullerene domain size at low temperature, but at room temperature, EBT does not represent a dominant loss pathway.
KW  - solar cells
KW  - electronic properties and materials
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-147413
VL  - 6
IS  - 29158
ER  - 
TY  - JOUR
A1  - Gottscholl, Andreas
A1  - Diez, Matthias
A1  - Soltamov, Victor
A1  - Kasper, Christian
A1  - Krauße, Dominik
A1  - Sperlich, Andreas
A1  - Kianinia, Mehran
A1  - Bradac, Carlo
A1  - Aharonovich, Igor
A1  - Dyakonov, Vladimir
T1  - Spin defects in hBN as promising temperature, pressure and magnetic field quantum sensors
JF  - Nature Communications
N2  - Spin defects in solid-state materials are strong candidate systems for quantum information technology and sensing applications. Here we explore in details the recently discovered negatively charged boron vacancies (V\(_B\)\(^−\)) in hexagonal boron nitride (hBN) and demonstrate their use as atomic scale sensors for temperature, magnetic fields and externally applied pressure. These applications are possible due to the high-spin triplet ground state and bright spin-dependent photoluminescence of the V\(_B\)\(^−\). Specifically, we find that the frequency shift in optically detected magnetic resonance measurements is not only sensitive to static magnetic fields, but also to temperature and pressure changes which we relate to crystal lattice parameters. We show that spin-rich hBN films are potentially applicable as intrinsic sensors in heterostructures made of functionalized 2D materials.
KW  - electronic properties and materials
KW  - qubits
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-261581
VL  - 12
IS  - 1
ER  -