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Electron-transport materials such as fullerenes are widely used in perovskite solar cells to selectively transfer the photogenerated electrons to the electrodes. In order to minimize losses at the interface between the fullerene and the electrode, it is important to reduce the energy difference between the transport level of the two materials. A common approach to reduce such energy mismatch is to increase the charge carrier density in the semiconductor through doping. A variety of molecular dopants have been reported to reduce (n-dope) fullerenes. However, most of them are either difficult to process or extremely air sensitive, with most n-dopants leading to the formation of undesirable side products. Dimers formed by 19-electron organometallic sandwich compounds combine strong reducing ability, clean reactivity, and moderate air stability, while being processable both from solution and in vacuum. In this work, we have investigated the use of pentamethylcyclopentadienyl mesitylene ruthenium dimer, (RuCp*mes) 2 , as a dopant for C 60 in fully vacuum-deposited n–i–p perovskite solar cells. The (RuCp*mes) 2 was either co-evaporated with the fullerene or deposited as a pure thin film on top of the transparent electrode prior to the deposition of the fullerene. It was found that both the co-evaporated blends and the bilayers are effective electron-transport layers, leading to solar cells with efficiencies up to 18%.
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Enhanced Open-Circuit Voltage in Perovskite Solar Cells with Open-Cage [60]Fullerene Derivatives as Electron-Transporting Materials
The synthesis, characterization, and incorporation of open-cage [60]fullerene derivatives as electron-transporting materials (ETMs) in perovskite solar cells (PSCs) with an inverted planar (p-i-n) structure is reported. Following optical and electrochemical characterization of the open-cage fullerenes 2a–c, p-i-n PSCs with a indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS)/perovskite/fullerene/Ag structure were prepared. The devices obtained from 2a–b exhibit competitive power conversion efficiencies (PCEs) and improved open-circuit voltage (Voc) values (>1.0 V) in comparison to a reference cell based on phenyl-C61-butyric-acid methyl-ester (PC61BM). These results are rationalized in terms of a) the higher passivation ability of the open-cage fullerenes with respect to the other fullerenes, and b) a good overlap between the highest occupied molecular orbital/lowest unoccupied molecular orbital (HOMO/LUMO) levels of 2a–b and the conduction band of the perovskite.
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- PAR ID:
- 10096662
- Date Published:
- Journal Name:
- Materials
- Volume:
- 12
- Issue:
- 8
- ISSN:
- 1996-1944
- Page Range / eLocation ID:
- 1314
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/ma12081314
