CH₃NH₃PbI₃ grain growth and interfacial properties in meso-structured perovskite solar cells fabricated by two-step deposition

Abstract

Although the two-step deposition (TSD) method is widely adopted for the high performance perovskite solar cells (PSCs), the CH3NH3PbI3 perovskite crystal growth mechanism during the TSD process and the photo-generated charge recombination dynamics in the mesoporous-TiO2 (mp-TiO2)/CH3NH3PbI3/hole transporting material (HTM) system remains unexploited. Herein, we modified the concentration of PbI2 (C (PbI2)) solution to control the perovskite crystal properties, and observed an abnormal CH3NH3PbI3 grain growth phenomenon atop mesoporous TiO2 film. To illustrate this abnormal grain growth mechanism, we propose that a grain ripening process is taking place during the transformation from PbI2 to CH3NH3PbI3, and discuss the PbI2 nuclei morphology, perovskite grain growing stage, as well as Pb:I atomic ratio difference among CH3NH3PbI3 grains with different morphology. These C (PbI2)-dependent perovskite morphologies resulted in varied charge carrier transfer properties throughout the mp-TiO2/CH3NH3PbI3/HTM hybrid, as illustrated by photoluminescence measurement. Furthermore, the effect of CH3NH3PbI3 morphology on light absorption and interfacial properties is investigated and correlated with the photovoltaic performance of PSCs.

Perovskite solar cells: must lead be replaced – and can it be done?

“…It is noteworthy that the maximum PCE of PSCs has been improved from 3.8 to 22.7% in just 7 years. This great success essentially arises from the exceptional optoelectronic properties of semiconducting halide perovskites, namely a high optical absorption coefficient, a tunable band gap, long carrier recombination lifetimes, and a high electron/hole mobility and transmission quality, along with small electron/hole effective masses and exciton binding energy [ 11–19 ].…”

Copper sulfide nanoparticles as hole-transporting-material in a fully-inorganic blocking layers n-i-p perovskite solar cells: Application and working insights

“…A statistical analysis of the photovoltaic parameters as a function of the HTM thickness is shown in 1, which is proportional to the rate employed during the spin-deposition. Interestingly, the optimal conditions for CuS were very different depending on the perovskite employed, probably due to the distinct surface roughness achieved for each layer [44,45]. In particular, we highlight the different morphology and grain-crystals observed in the cross-sectional scanning electron microscopy (SEM) images presented in Fig.…”

Optoelectronic and morphology properties of perovskite/silicon interface layer for tandem solar cell application

“…Higher viscosity indicated that more solute (MAI and PbI 2 ) concentration was added to the same volume of solvent (DMF) to synthesize higher concentration precursor solution. Higher concentration perovskite deposited on FTO produced darker film because of higher PbI 2 content added in perovskite compound . The viscosity character of the 1.2M MAPbI 3 perovskite solution was more than 0.8M and 1.0M.…”

“…Based on previous study, there were a few methods to form MAPbI 3 perovskite thin film that were solution or vapor processing. The methods for solution processing technique were one‐step precursor deposition and two‐step sequential deposition method . Then enough thin film anneal time was needed for the crystallization of perovskite crystals to be complete .…”