TY  - JOUR
A1  - Perdigón-Toro, Lorena
A1  - Le Quang Phuong, 
A1  - Eller, Fabian
A1  - Freychet, Guillaume
A1  - Saglamkaya, Elifnaz
A1  - Khan, Jafar
A1  - Wei, Qingya
A1  - Zeiske, Stefan
A1  - Kroh, Daniel
A1  - Wedler, Stefan
A1  - Koehler, Anna
A1  - Armin, Ardalan
A1  - Laquai, Frederic
A1  - Herzig, Eva M.
A1  - Zou, Yingping
A1  - Shoaee, Safa
A1  - Neher, Dieter
T1  - Understanding the role of order in Y-series non-fullerene solar cells to realize high open-circuit voltages
JF  - Advanced energy materials
N2  - Non-fullerene acceptors (NFAs) as used in state-of-the-art organic solar cells feature highly crystalline layers that go along with low energetic disorder. 
Here, the crucial role of energetic disorder in blends of the donor polymer PM6 with two Y-series NFAs, Y6, and N4 is studied. 
By performing temperature-dependent charge transport and recombination studies, a consistent picture of the shape of the density of state distributions for free charges in the two blends is developed, allowing an analytical description of the dependence of the open-circuit voltage V-OC on temperature and illumination intensity. 

Disorder is found to influence the value of the V-OC at room temperature, but also its progression with temperature. Here, the PM6:Y6 blend benefits substantially from its narrower state distributions. 
The analysis also shows that the energy of the equilibrated free charge population is well below the energy of the NFA singlet excitons for both blends and possibly below the energy of the populated charge transfer manifold, indicating a down-hill driving force for free charge formation. 
It is concluded that energetic disorder of charge-separated states has to be considered in the analysis of the photovoltaic properties, even for the more ordered PM6:Y6 blend.
KW  - energetic disorder
KW  - non-fullerene acceptors
KW  - open-circuit voltage
KW  - organic solar cells
Y1  - 2022
U6  - https://doi.org/10.1002/aenm.202103422
SN  - 1614-6832
SN  - 1614-6840
VL  - 12
IS  - 12
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Perdigón-Toro, Lorena
A1  - Le Quang Phuong, 
A1  - Zeiske, Stefan
A1  - Vandewal, Koen
A1  - Armin, Ardalan
A1  - Shoaee, Safa
A1  - Neher, Dieter
T1  - Excitons dominate the emission from PM6
BT  - Y6 solar cells, but this does not help the open-circuit voltage of the device
JF  - ACS energy letters / American Chemical Society
N2  - Non-fullerene acceptors (NFAs) are far more emissive than their fullerene-based counterparts. Here, we study the spectral properties of photocurrent generation and recombination of the blend of the donor polymer PM6 with the NFA Y6. We find that the radiative recombination of free charges is almost entirely due to the re-occupation and decay of Y6 singlet excitons, but that this pathway contributes less than 1% to the total recombination. As such, the open-circuit voltage of the PM6:Y6 blend is determined by the energetics and kinetics of the charge-transfer (CT) state. Moreover, we find that no information on the energetics of the CT state manifold can be gained from the low-energy tail of the photovoltaic external quantum efficiency spectrum, which is dominated by the excitation spectrum of the Y6 exciton. We, finally, estimate the charge-separated state to lie only 120 meV below the Y6 singlet exciton energy, meaning that this blend indeed represents a high-efficiency system with a low energetic offset.
Y1  - 2021
U6  - https://doi.org/10.1021/acsenergylett.0c02572
SN  - 2380-8195
VL  - 6
IS  - 2
SP  - 557
EP  - 564
PB  - American Chemical Society
CY  - Washington
ER  -