Substrate heating is the most common method for controlling crystallization during spray coating. However, due to poor controllability during substrate heating, the sprayed films have variable thicknesses and rich pores, which limit the efficiency of the device. Here, hot air blowing was applied to spray coating to promote the crystallization of perovskite films under ambient conditions. Upon employing a hot air blowing method that stimulated uniformly distributed nuclei growth, the pinhole-free and thickness-controllable perovskite film was prepared. This enabled more reproducible high-quality perovskite films to achieve a power conversion efficiency of 13.5% and obtain a stabilized power output of >12% in ambient conditions.
The
best research-cell efficiency for quantum dot solar cells has
boosted from 11.6 to 18.1% within 5 years due to the evolution of
perovskite quantum dots (PQDs) that are being intensively developed
along with the flourishing of perovskite thin-film photovoltaics.
During the fabrication of PQD devices, as far as we know, methyl acetate
(MeOAc) is an ineluctable solvent in ligand exchange for producing
highly efficient solar cells. Nevertheless, the reproducibility for
PQD solar cells using MeOAc treatment is poor since it has to make
a trade-off between removing long-chain organic ligands for high charge
transport and keeping them for the stabilization of the black crystal
phase. Herein, we demonstrate the degree of MeOAc treatment on CsPbI3 PQD solid films in detail and clarify that MeOAc treatment
is able to not only remove the oleyl ligands for promoting the charge
transport but also passivate the surface defects in the CsPbI3 PQD solid films. It is noted that immoderate MeOAc treatment
could induce the formation of the δ-phase, leading to the degradation
of device performance. After locating the balance for MeOAc treatment,
the CsPbI3 PQD solar cells are fabricated and optimized
without using any additional modifications except MeOAc treatment,
and these additive-free devices possess a conversion efficiency surpassing
12%.
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.
Diatomite is an inorganic natural resource in large reserve. This study consists of two phases to evaluate the effects of diatomite on asphalt mixtures. In the first phase, we characterized the diatomite in terms of mineralogical properties, chemical compositions, particle size distribution, mesoporous distribution, morphology, and IR spectra. In the second phase, road performances, referring to the permanent deformation, crack, fatigue, and moisture resistance, of asphalt mixtures with diatomite were investigated. The characterization of diatomite exhibits that it is a porous material with high SiO2 content and large specific surface area. It contributes to asphalt absorption and therefore leads to bonding enhancement between asphalt and aggregate. However, physical absorption instead of chemical reaction occurs according to the results of FTIR. The resistance of asphalt mixtures with diatomite to permanent deformation and moisture are superior to those of the control mixtures. But, the addition of diatomite does not help to improve the crack and fatigue resistance of asphalt mixture.
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.
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