The development of perovskite solar cells (PSCs) has progressed rapidly because of their high efficiency and low cost. The performance of PSCs is predominantly determined by the quality of the perovskite films, which is controlled by the fabrication process. The comprehensive and in-depth understanding of the nucleation, crystallization, and growth process are imperative for the further advancement of large-scale manufacturing of high-quality perovskite films. In this work, the simple process parameters of perovskite thin films were systematically optimized at ambient air, such as containing the thickness of the perovskite thin film, the anti-solvent bath, and the thermal annealing time. Through these simple processes, the wet film, solvent volatilization, and crystallization of perovskite films can be controlled and optimized. After optimizing the spraying conditions, the champion power conversion efficiency (PCE) of the PSCs achieved 20.6% (reverse scan) and had little hysteresis in the current density−voltage (J− V). In addition, the unsealed device retained 85% of its original PCE and showed excellent long-term stability after 650 h of storage in the drying tower.
Obtaining a perovskite light-absorbing layer with good crystallization, low defect concentration, good stability, and well-matched energy levels is critical to obtaining high-efficiency perovskite solar cells (PSCs). Here, a hybrid PSC with a graded band gap is explored using MAPbBr 3 (MA = CH 3 NH 3 ) and MAPbBr 0.9 I 2.1 quantum dots (QDs) as component cells. We have creatively designed a solar cell device with a double-QD structure [indium tin oxide (ITO)/SnO 2 /perovskite:MAPbBr 3 QDs/MAPbBr 0.9 I 2.1 QDs/Spiro-OMeTAD/Au]. A better crystal film of the perovskite absorption layer can be obtained because the MAPbBr 3 QDs are doped in an antisolvent, which induces nucleation and growth in the polycrystalline perovskite. In addition, we expect that digestive ripening occurred in the crystallization, and the oleic acid ligands on the surface of the QDs disintegrate during the doping process and transfer to the surface of the perovskite absorption layer finally; it follows that the hydrophobicity and stability of the perovskite film are greatly enhanced. Moreover, a thin film of MAPbBr 0.9 I 2.1 QDs is introduced between the perovskite absorption layer and the hole layer, acting as an energy-level ladder, which leads to well-matched energy levels, an increase in fill factor (FF), and an enhanced hole transport capability. In particular, the mechanism of the crystallization process involving the effect of oleic acid ligands on the interior and surface of the perovskite film is fully discussed here. The final research results from the PSCs show that both high efficiency and long-term stability are achieved successfully by this design strategy.
Among
deposition methods, ultrasonic spray-coating has particularly
strong potential for large-scale production due to its low cost and
capability to produce thin films with large-scale areas for industrial
applications. In this work, SnO2 electron transport layers
(ETLs) were successfully prepared via ultrasonic spray-coating at
a low temperature. A series of spraying parameters were optimized
to adjust the drying process. Finally, compact pinhole-free ETLs with
high transmittance and preeminent electron migration efficiency were
obtained. The small-area perovskite solar cells (PSCs) (0.29 cm2) were fabricated based on the aforesaid SnO2 ETLs
exhibiting a distinguished power conversion efficiency (PCE) of 18.72%.
More than 85% of the original PCE was retained after the cells were
stored in a drying tower (room temperature (RT), 30% relative humidity
(RH)) for 1000 h without encapsulation, which reflects the remarkable
stability of the devices. Moreover, minimodules (4 cm × 4 cm)
were also fabricated successfully with a PCE of 10.57%.
Molecular
ferroelectrics with narrow bandgaps has great potential
in the photoelectric field, but the outstanding species are still
scarce. Herein, [C6N2H18][SbI5] has been demonstrated as a room-temperature (RT) molecular
ferroelectric and applied to the organic–inorganic hybrid solar
cells as the light-absorbing layer. The polar orthorhombic structure
was solved by single-crystal XRD. The inherent RT ferroelectricity
was revealed by hysteresis measurements with superior saturation polarization
(P
s), remanent polarization (P
r), and coercive field (E
c) as 12.55 μC/cm2, 10.78 μC/cm2, and 0.33 kV/cm, respectively. The [C6N2H18][SbI5]-based solar device exhibits a significant
photovoltaic (PV) effect under AM 1.5 G illumination with V
oc ∼ 0.43 V, J
sc ∼ 35.17 μA/cm2, and a fast response time
of ∼0.33 ms. A dramatical enhancement in PV performance has
been achieved by turning the ferroelectric polarization, leading to
the maximum V
oc ∼ 0.75 V, J
sc ∼ 1.09 mA/cm2, and a power
conversion efficiency (PCE) of 0.29%. This work offers a bright avenue
for molecular ferroelectrics in optoelectronic devices.
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