TY  - JOUR
A1  - Zhang, Shanshan
A1  - Hosseini, Seyed Mehrdad
A1  - Gunder, Rene
A1  - Petsiuk, Andrei
A1  - Caprioglio, Pietro
A1  - Wolff, Christian Michael
A1  - Shoaee, Safa
A1  - Meredith, Paul
A1  - Schorr, Susan
A1  - Unold, Thomas
A1  - Burn, Paul L.
A1  - Neher, Dieter
A1  - Stolterfoht, Martin
T1  - The Role of Bulk and Interface Recombination in High-Efficiency Low-Dimensional Perovskite Solar Cells
JF  - Advanced materials
N2  - 2D Ruddlesden-Popper perovskite (RPP) solar cells have excellent environmental stability. However, the power conversion efficiency (PCE) of RPP cells remains inferior to 3D perovskite-based cells. Herein, 2D (CH3(CH2)(3)NH3)(2)(CH3NH3)(n-1)PbnI3n+1 perovskite cells with different numbers of [PbI6](4-) sheets (n = 2-4) are analyzed. Photoluminescence quantum yield (PLQY) measurements show that nonradiative open-circuit voltage (V-OC) losses outweigh radiative losses in materials with n > 2. The n = 3 and n = 4 films exhibit a higher PLQY than the standard 3D methylammonium lead iodide perovskite although this is accompanied by increased interfacial recombination at the top perovskite/C-60 interface. This tradeoff results in a similar PLQY in all devices, including the n = 2 system where the perovskite bulk dominates the recombination properties of the cell. In most cases the quasi-Fermi level splitting matches the device V-OC within 20 meV, which indicates minimal recombination losses at the metal contacts. The results show that poor charge transport rather than exciton dissociation is the primary reason for the reduction in fill factor of the RPP devices. Optimized n = 4 RPP solar cells had PCEs of 13% with significant potential for further improvements.
KW  - 2D perovskites
KW  - interface recombination
KW  - perovskite solar cells
KW  - photoluminescence
KW  - V-OC loss
Y1  - 2019
U6  - https://doi.org/10.1002/adma.201901090
SN  - 0935-9648
SN  - 1521-4095
VL  - 31
IS  - 30
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Zhang, Shanshan
A1  - Stolterfoht, Martin
A1  - Armin, Ardalan
A1  - Lin, Qianqian
A1  - Zu, Fengshuo
A1  - Sobus, Jan
A1  - Jin, Hui
A1  - Koch, Norbert
A1  - Meredith, Paul
A1  - Burn, Paul L.
A1  - Neher, Dieter
T1  - Interface Engineering of Solution-Processed Hybrid Organohalide Perovskite Solar Cells
JF  - ACS applied materials & interfaces
N2  - Engineering the interface between the perovskite absorber and the charge-transporting layers has become an important method for improving the charge extraction and open-circuit voltage (V-OC) of hybrid perovskite solar cells. Conjugated polymers are particularly suited to form the hole-transporting layer, but their hydrophobicity renders it difficult to solution-process the perovskite absorber on top. Herein, oxygen plasma treatment is introduced as a simple means to change the surface energy and work function of hydrophobic polymer interlayers for use as p-contacts in perovskite solar cells. We find that upon oxygen plasma treatment, the hydrophobic surfaces of different prototypical p-type polymers became sufficiently hydrophilic to enable subsequent perovskite junction processing. In addition, the oxygen plasma treatment also increased the ionization potential of the polymer such that it became closer to the valance band energy of the perovskite. It was also found that the oxygen plasma treatment could increase the electrical conductivity of the p-type polymers, facilitating more efficient charge extraction. On the basis of this concept, inverted MAPbI(3) perovskite devices with different oxygen plasma-treated polymers such as P3HT, P3OT, polyTPD, or PTAA were fabricated with power conversion efficiencies of up to 19%.
KW  - organohalide lead perovskites
KW  - solar cells
KW  - surface wetting
KW  - work function
KW  - oxygen plasma
KW  - transport layer
Y1  - 2018
U6  - https://doi.org/10.1021/acsami.8b02503
SN  - 1944-8244
VL  - 10
IS  - 25
SP  - 21681
EP  - 21687
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Stolterfoht, Martin
A1  - Wolff, Christian Michael
A1  - Marquez, Jose A.
A1  - Zhang, Shanshan
A1  - Hages, Charles J.
A1  - Rothhardt, Daniel
A1  - Albrecht, Steve
A1  - Burn, Paul L.
A1  - Meredith, Paul
A1  - Unold, Thomas
A1  - Neher, Dieter
T1  - Visualization and suppression of interfacial recombination for high-efficiency large-area pin perovskite solar cells
JF  - Nature Energy
N2  - The performance of perovskite solar cells is predominantly limited by non-radiative recombination, either through trap-assisted recombination in the absorber layer or via minority carrier recombination at the perovskite/transport layer interfaces. Here, we use transient and absolute photoluminescence imaging to visualize all non-radiative recombination pathways in planar pintype perovskite solar cells with undoped organic charge transport layers. We find significant quasi-Fermi-level splitting losses (135 meV) in the perovskite bulk, whereas interfacial recombination results in an additional free energy loss of 80 meV at each individual interface, which limits the open-circuit voltage (V-oc) of the complete cell to similar to 1.12 V. Inserting ultrathin interlayers between the perovskite and transport layers leads to a substantial reduction of these interfacial losses at both the p and n contacts. Using this knowledge and approach, we demonstrate reproducible dopant-free 1 cm(2) perovskite solar cells surpassing 20% efficiency (19.83% certified) with stabilized power output, a high V-oc (1.17 V) and record fill factor (>81%).
KW  - Energy science and technology
KW  - Solar cells
Y1  - 2018
U6  - https://doi.org/10.1038/s41560-018-0219-8
SN  - 2058-7546
VL  - 3
IS  - 10
SP  - 847
EP  - 854
PB  - Nature Publ. Group
CY  - London
ER  -