TY  - JOUR
A1  - Zu, Fengshuo
A1  - Amsalem, Patrick
A1  - Egger, David A.
A1  - Wang, Rongbin
A1  - Wolff, Christian Michael
A1  - Fang, Honghua
A1  - Loi, Maria Antonietta
A1  - Neher, Dieter
A1  - Kronik, Leeor
A1  - Duhm, Steffen
A1  - Koch, Norbert
T1  - Constructing the Electronic Structure of CH3NH3PbI3 and CH3NH3PbBr3 Perovskite Thin Films from Single-Crystal Band Structure Measurements
JF  - The journal of physical chemistry letters
N2  - Photovoltaic cells based on halide perovskites, possessing remarkably high power conversion efficiencies have been reported. To push the development of such devices further, a comprehensive and reliable understanding of their electronic properties is essential but presently not available. To provide a solid foundation for understanding the electronic properties of polycrystalline thin films, we employ single-crystal band structure data from angle-resolved photoemission measurements. For two prototypical perovskites (CH3NH3PbBr3 and CH3NH3PbI3), we reveal the band dispersion in two high-symmetry directions and identify the global valence band maxima. With these benchmark data, we construct "standard" photoemission spectra from polycrystalline thin film samples and resolve challenges discussed in the literature for determining the valence band onset with high reliability. Within the framework laid out here, the consistency of relating the energy level alignment in perovskite-based photovoltaic and optoelectronic devices with their functional parameters is substantially enhanced.
Y1  - 2019
U6  - https://doi.org/10.1021/acs.jpclett.8b03728
SN  - 1948-7185
VL  - 10
IS  - 3
SP  - 601
EP  - 609
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - GEN
A1  - Wolff, Christian Michael
A1  - Canil, Laura
A1  - Rehermann, Carolin
A1  - Nguyen, Ngoc Linh
A1  - Zu, Fengshuo
A1  - Ralaiarisoa, Maryline
A1  - Caprioglio, Pietro
A1  - Fiedler, Lukas
A1  - Stolterfoht, Martin
A1  - Kogikoski, Junior, Sergio
A1  - Bald, Ilko
A1  - Koch, Norbert
A1  - Unger, Eva L.
A1  - Dittrich, Thomas
A1  - Abate, Antonio
A1  - Neher, Dieter
T1  - Correction to 'Perfluorinated self-assembled monolayers enhance the stability and efficiency of inverted perovskite solar cells' (2020, 14 (2), 1445−1456)
T2  - ACS nano
Y1  - 2020
U6  - https://doi.org/10.1021/acsnano.0c08081
SN  - 1936-0851
SN  - 1936-086X
VL  - 14
IS  - 11
SP  - 16156
EP  - 16156
PB  - American Chemical Society
CY  - Washington, DC
ER  - 
TY  - JOUR
A1  - Neusser, David
A1  - Sun, Bowen
A1  - Tan, Wen Liang
A1  - Thomsen, Lars
A1  - Schultz, Thorsten
A1  - Perdigon-Toro, Lorena
A1  - Koch, Norbert
A1  - Shoaee, Safa
A1  - McNeill, Christopher R.
A1  - Neher, Dieter
A1  - Ludwigs, Sabine
T1  - Spectroelectrochemically determined energy levels of PM6:Y6 blends and their relevance to solar cell performance
JF  - Journal of materials chemistry : C, Materials for optical and electronic devices
N2  - Recent advances in organic solar cell performance have been mainly driven forward by combining high-performance p-type donor-acceptor copolymers (e.g.PM6) and non-fullerene small molecule acceptors (e.g.Y6) as bulk-heterojunction layers. A general observation in such devices is that the device performance, e.g., the open-circuit voltage, is strongly dependent on the processing solvent. While the morphology is a typically named key parameter, the energetics of donor-acceptor blends are equally important, but less straightforward to access in the active multicomponent layer. Here, we propose to use spectral onsets during electrochemical cycling in a systematic spectroelectrochemical study of blend films to access the redox behavior and the frontier orbital energy levels of the individual compounds. Our study reveals that the highest occupied molecular orbital offset (Delta E-HOMO) in PM6:Y6 blends is similar to 0.3 eV, which is comparable to the binding energy of Y6 excitons and therefore implies a nearly zero driving force for the dissociation of Y6 excitons. Switching the PM6 orientation in the blend films from face-on to edge-on in bulk has only a minor influence on the positions of the energy levels, but shows significant differences in the open circuit voltage of the device. We explain this phenomenon by the different interfacial molecular orientations, which are known to affect the non-radiative decay rate of the charge-transfer state. We compare our results to ultraviolet photoelectron spectroscopy data, which shows distinct differences in the HOMO offsets in the PM6:Y6 blend compared to neat films. This highlights the necessity to measure the energy levels of the individual compounds in device-relevant blend films.
Y1  - 2022
U6  - https://doi.org/10.1039/d2tc01918c
SN  - 2050-7526
SN  - 2050-7534
VL  - 10
IS  - 32
SP  - 11565
EP  - 11578
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  -