TY  - JOUR
A1  - Nikolis, Vasileios C.
A1  - Benduhn, Johannes
A1  - Holzmueller, Felix
A1  - Piersimoni, Fortunato
A1  - Lau, Matthias
A1  - Zeika, Olaf
A1  - Neher, Dieter
A1  - Koerner, Christian
A1  - Spoltore, Donato
A1  - Vandewal, Koen
T1  - Reducing Voltage Losses in Cascade Organic Solar Cells while Maintaining High External Quantum Efficiencies
T2  - dvanced energy materials
N2  - High photon energy losses limit the open-circuit voltage (V-OC) and power conversion efficiency of organic solar cells (OSCs). In this work, an optimization route is presented which increases the V-OC by reducing the interfacial area between donor (D) and acceptor (A). This optimization route concerns a cascade device architecture in which the introduction of discontinuous interlayers between alpha-sexithiophene (alpha-6T) (D) and chloroboron subnaphthalocyanine (SubNc) (A) increases the V-OC of an alpha-6T/SubNc/SubPc fullerene-free cascade OSC from 0.98 V to 1.16 V. This increase of 0.18 V is attributed solely to the suppression of nonradiative recombination at the D-A interface. By accurately measuring the optical gap (E-opt) and the energy of the charge-transfer state (E-CT) of the studied OSC, a detailed analysis of the overall voltage losses is performed. E-opt - qV(OC) losses of 0.58 eV, which are among the lowest observed for OSCs, are obtained. Most importantly, for the V-OC-optimized devices, the low-energy (700 nm) external quantum efficiency (EQE) peak remains high at 79%, despite a minimal driving force for charge separation of less than 10 meV. This work shows that low-voltage losses can be combined with a high EQE in organic photovoltaic devices.
KW  - energy losses
KW  - nonradiative recombination
KW  - open-circuit voltage
KW  - organic solar cells
KW  - voltage losses
Y1  - 2017
UR  - https://publishup.uni-potsdam.de/frontdoor/index/index/docId/46182
SN  - 1614-6832
SN  - 1614-6840
VL  - 7
SP  - 122
EP  - 136
PB  - Wiley-VCH
CY  - Weinheim
ER  -