All perovskite samples were prepared
following the method described in our previous work.29 (link) In summary, FTO substrates were cleaned using RBS detergent,
ethanol, and acetone in an ultrasound bath during several steps of
30 min. Compact TiO2 was deposited by spray pyrolysis at
450 °C, obtaining an anatase compact layer of around 20–30
nm of thickness. On top of this layer, 50 μL of a TiO2-mp solution was spin-coated at 4000 rpm, with an acceleration of
2000 rpm/s, during 10 s and sintered at 450 °C during 30 min
in air, forming a mesoporous scaffold of TiO2 nanoparticles.
After that, 100 μL of 35 mM lithium bistrifluoromethanesulfonimidate
(Li-TFSI) in acetonitrile was spin-coated (3000 rpm for 10 s) and
the substrates were thermally annealed again in air at 450 °C
for 30 min. After this process, the substrates were brought directly
into a glovebox.
Perovskite precursor solutions and thin films
were prepared inside a N2-filled glovebox. Two master solutions
were prepared in advance: (a) 0.9 M PbI2 and 0.9 M FAI
and (b) 0.9 M PbI2 and 0.9 M CsI. The final solution was
prepared right before deposition by pouring solution (a) into solution
(b) in the proportion a:b = 83:17, obtaining a perovskite final composition
of Cs0.17FA0.83PbI3. The solvent
was anhydrous DMF:DMSO (4:1) for all solutions. FA salts were bought
from Dyesol, lead salts from TCI, solvents from Fisher, and the remaining
chemicals from Sigma-Aldrich. All chemicals were used as received
without further treatment. Seventy-five microliters of the precursor
solution was spread over the substrate and spin-coated using a two-step
program. The first step used a rotation speed of 1000 rpm with an
acceleration of 200 rpm/s for 10 s, followed by a second step in which
the films were spun at 6000 rpm for 15 s using an acceleration of
2000 rpm/s. After 20 ss, 200 μL of anhydrous chlorobenzene was
applied on the spinning film. Directly after spin coating, the films
were annealed on a hotplate at 100 °C for approximately 1 h.
The polymer P3 was synthesized according to the method described
previously.35 (link) For deposition, a P3 solution
with a concentration of 5 mg/mL in chlorobenzene was prepared and
stirred in the ambient environment to fully dissolve the polymer and
then spin-coated onto the perovskite or FTO substrates at 3000 rpm
for 30 s.
Gold electrodes were evaporated using a Leica EM MED020
thermal
evaporator at a pressure below 7 × 10–3 mbar.
The thickness was measured using a Leica EM QSG100 quartz microbalance.
To avoid short circuits, a mask was used to prevent any gold deposition
on the side opposite to the etched substrate. A 7 nm gold layer was
deposited using this mask; thereafter, the chamber was vented, and
an additional mask was added for the evaporation of the thick (>50
nm) gold contact and the bus bars.
following the method described in our previous work.29 (link) In summary, FTO substrates were cleaned using RBS detergent,
ethanol, and acetone in an ultrasound bath during several steps of
30 min. Compact TiO2 was deposited by spray pyrolysis at
450 °C, obtaining an anatase compact layer of around 20–30
nm of thickness. On top of this layer, 50 μL of a TiO2-mp solution was spin-coated at 4000 rpm, with an acceleration of
2000 rpm/s, during 10 s and sintered at 450 °C during 30 min
in air, forming a mesoporous scaffold of TiO2 nanoparticles.
After that, 100 μL of 35 mM lithium bistrifluoromethanesulfonimidate
(Li-TFSI) in acetonitrile was spin-coated (3000 rpm for 10 s) and
the substrates were thermally annealed again in air at 450 °C
for 30 min. After this process, the substrates were brought directly
into a glovebox.
Perovskite precursor solutions and thin films
were prepared inside a N2-filled glovebox. Two master solutions
were prepared in advance: (a) 0.9 M PbI2 and 0.9 M FAI
and (b) 0.9 M PbI2 and 0.9 M CsI. The final solution was
prepared right before deposition by pouring solution (a) into solution
(b) in the proportion a:b = 83:17, obtaining a perovskite final composition
of Cs0.17FA0.83PbI3. The solvent
was anhydrous DMF:DMSO (4:1) for all solutions. FA salts were bought
from Dyesol, lead salts from TCI, solvents from Fisher, and the remaining
chemicals from Sigma-Aldrich. All chemicals were used as received
without further treatment. Seventy-five microliters of the precursor
solution was spread over the substrate and spin-coated using a two-step
program. The first step used a rotation speed of 1000 rpm with an
acceleration of 200 rpm/s for 10 s, followed by a second step in which
the films were spun at 6000 rpm for 15 s using an acceleration of
2000 rpm/s. After 20 ss, 200 μL of anhydrous chlorobenzene was
applied on the spinning film. Directly after spin coating, the films
were annealed on a hotplate at 100 °C for approximately 1 h.
The polymer P3 was synthesized according to the method described
previously.35 (link) For deposition, a P3 solution
with a concentration of 5 mg/mL in chlorobenzene was prepared and
stirred in the ambient environment to fully dissolve the polymer and
then spin-coated onto the perovskite or FTO substrates at 3000 rpm
for 30 s.
Gold electrodes were evaporated using a Leica EM MED020
thermal
evaporator at a pressure below 7 × 10–3 mbar.
The thickness was measured using a Leica EM QSG100 quartz microbalance.
To avoid short circuits, a mask was used to prevent any gold deposition
on the side opposite to the etched substrate. A 7 nm gold layer was
deposited using this mask; thereafter, the chamber was vented, and
an additional mask was added for the evaporation of the thick (>50
nm) gold contact and the bus bars.
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