TY  - JOUR
A1  - Stolterfoht, Martin
A1  - Caprioglio, Pietro
A1  - Wolff, Christian Michael
A1  - Marquez, Jose A.
A1  - Nordmann, Joleik
A1  - Zhang, Shanshan
A1  - Rothhardt, Daniel
A1  - Hörmann, Ulrich
A1  - Amir, Yohai
A1  - Redinger, Alex
A1  - Kegelmann, Lukas
A1  - Zu, Fengshuo
A1  - Albrecht, Steve
A1  - Koch, Norbert
A1  - Kirchartz, Thomas
A1  - Saliba, Michael
A1  - Unold, Thomas
A1  - Neher, Dieter
T1  - The impact of energy alignment and interfacial recombination on the internal and external open-circuit voltage of perovskite solar cells
JF  - Energy & environmental science
N2  - Charge transport layers (CTLs) are key components of diffusion controlled perovskite solar cells, however, they can induce additional non-radiative recombination pathways which limit the open circuit voltage (V-OC) of the cell. In order to realize the full thermodynamic potential of the perovskite absorber, both the electron and hole transport layer (ETL/HTL) need to be as selective as possible. By measuring the photoluminescence yield of perovskite/CTL heterojunctions, we quantify the non-radiative interfacial recombination currents in pin- and nip-type cells including high efficiency devices (21.4%). Our study comprises a wide range of commonly used CTLs, including various hole-transporting polymers, spiro-OMeTAD, metal oxides and fullerenes. We find that all studied CTLs limit the V-OC by inducing an additional non-radiative recombination current that is in most cases substantially larger than the loss in the neat perovskite and that the least-selective interface sets the upper limit for the V-OC of the device. Importantly, the V-OC equals the internal quasi-Fermi level splitting (QFLS) in the absorber layer only in high efficiency cells, while in poor performing devices, the V-OC is substantially lower than the QFLS. Using ultraviolet photoelectron spectroscopy and differential charging capacitance experiments we show that this is due to an energy level mis-alignment at the p-interface. The findings are corroborated by rigorous device simulations which outline important considerations to maximize the V-OC. This work highlights that the challenge to suppress non-radiative recombination losses in perovskite cells on their way to the radiative limit lies in proper energy level alignment and in suppression of defect recombination at the interfaces.
Y1  - 2019
U6  - https://doi.org/10.1039/c9ee02020a
SN  - 1754-5692
SN  - 1754-5706
VL  - 12
IS  - 9
SP  - 2778
EP  - 2788
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  -