Off-Stoichiometric Methylammonium Iodide Passivated Large-Grain Perovskite Film in Ambient Air for Efficient Inverted Solar Cells

Abstract

Hot-casting is a promising technique of depositing high-quality organic–inorganic hybrid perovskite thin films with large crystal grain size. Here, we reported the that the crystallinity and grain size of perovskite films could be systematically tailored by modulating the stoichiometry of the precursor solution in the hot-casting process under ambient condition with a relative humidity of 40%. It was found that a slight excess of methylammonium iodide (MAI) in the precursor solution could effectively compensate the MAI loss due to the high substrate temperature. A significant increase in the grain size and crystallinity of the perovskite film was observed together with a decrease in defect density and a carrier concentration enhancement in MAI-rich samples. The corresponding devices exhibited a notable increase in fill factor (up to 80.70%) and short-circuit current density. In addition, in MAI-deficient samples, an enrichment of PbI2 at the grain boundaries was directly observed by optical microscopy and laser confocal microscopy. Time-resolved photoluminescence spectroscopy revealed an increase in the charge carrier lifetime in the MAI-deficient samples, which was in line with the previous results with a small amount of excess PbI2 in the perovskite film. This work highlights a new strategy to prepare high-quality perovskite thin films with excellent crystal quality under ambient condition.

From Groundwork to Efficient Solar Cells: On the Importance of the Substrate Material in Co‐Evaporated Perovskite Solar Cells

“…Although lateral grain sizes are slightly larger for thin films grown on top of SnO 2 , grain sizes for all thin films fabricated in this study remain below 300 nm and consequently significantly below the values that are commonly achieved for solution-processed thin films. [84][85][86][87] Based on these observations, it is concluded that the substrate material strongly affects not only crystallographic properties of the perovskite crystallites, but also impacts the conversion of PbI 2 into perovskite and, thereby, the composition of the resultant perovskite thin film. This goes beyond previous studies, where detailed investigations showed that the substrate material can influence the composition and electronic structure of the perovskite thin film close to the underlying charge transport layer.…”

Electroluminescence Principle and Performance Improvement of Metal Halide Perovskite Light‐Emitting Diodes

“…Therefore, excess organic halides can be added to the precursor solution to compensate for the loss of organic halides in perovskites. [ 126–129 ] This strategy is also appropriate for inorganic perovskite devices. Lin et al.…”

Vacancy defect modulation in hot-casted NiO film for efficient inverted planar perovskite solar cells

“…Among all device structures, the p-i-n planar structure has emerged as a strong competitor due to its excellent long-term stability and negligible hysteresis [6][7][8][9][10][11] . Nonstoichiometric metal oxides (such as CuO x [12] , MoO x [13] , and NiO x [14][15][16] ) have been often selected as the hole transport layers (HTLs) due to their low cost and tunable optoelectronic properties. In particular, NiO x is a p-type semiconductor with a wide optical band gap of approximately 3.4-4.0 eV, a high conduction band edge, and high chemical stability and hole mobility [15,[17][18][19][20] .…”