Abstract
The formation of methylammonium lead iodide (CH3NH3PbI3) perovskite into mesoporous titania (TiO2) scaffold via a sequential deposition method is known to offer high quality films for good photovoltaic device performance. The local kinetics at the lower interface between the mesoporous TiO2 film and the collecting electrode govern perovskite growth and formation. Here, we have used a NanoPlasmonic Sensing (NPS) approach with gold (Au) nanosensors to monitor the formation of CH3NH3PbI3 perovskite at the lower interface of up to 650 nm mesoporous TiO2 films. This technique provides time-resolved spectral shifts of the localized surface plasmon resonance at different operating temperatures and methylammonium iodide (CH3NH3I3) concentrations by recording changes in the local vicinity of the Au nanosensors at the mesoporous TiO2 film interface. Analytical studies included ellipsometry, scanning electron microscopy, X-ray diffraction, and photoluminescence spectroscopy. The results show that both the intensity of the NPS response and NPS rate constants are correlated with the operating concentrations and temperatures of CH3NH3I3 as well as CH3NH3PbI3 perovskite growth in mesoporous TiO2.
Highlights
INTRODUCTIONPerovskite solar cells based on alkylammonium metal trihalide light-absorption layer offer the promise for a breakthrough for generation solar devices. the attractive class of methylammonium lead iodide (CH3NH3PbI3: MAPbI3) exhibit several advantages of unique optical characteristics with bandgap tunability, high mobility and long carrier lifetime, and long-range electron-hole diffusion lengths. Perovskite films have been deposited via either thermal evaporation or solution processing. The two common pathways often applied during film formation are the one-step method in which the reactants are thoroughly mixed prior to deposition and the two-step route where the precursors are sequentially deposited. Remarkably, much better control over the perovskite morphology was observed using the two-deposition route to either thick or thin mesoscopic metal oxides. The growth and fabrication conditions of these films significantly affect the performance of the fabricated photovoltaic devices
We demonstrate the use of nanoplasmonic sensing (NPS) to detect the formation kinetics of CH3NH3PbI3 perovskite at the interface of up to ∼650 nm compact/mesoporous TiO2 films with Au nanodisks
The coated Au sensors were found to be sensitive to the change in the heating program (25–53 ○C) prior to the min. Different concentrations of CH3NH3I (MAI) injection (Fig. S1, supplementary material); the actual sensor peak position and extinction shifts detected in this work are tailored to present the sensor response after MAI injections as addressed hereafter
Summary
Perovskite solar cells based on alkylammonium metal trihalide light-absorption layer offer the promise for a breakthrough for generation solar devices. the attractive class of methylammonium lead iodide (CH3NH3PbI3: MAPbI3) exhibit several advantages of unique optical characteristics with bandgap tunability, high mobility and long carrier lifetime, and long-range electron-hole diffusion lengths. Perovskite films have been deposited via either thermal evaporation or solution processing. The two common pathways often applied during film formation are the one-step method in which the reactants are thoroughly mixed prior to deposition and the two-step route where the precursors are sequentially deposited. Remarkably, much better control over the perovskite morphology was observed using the two-deposition route to either thick or thin mesoscopic metal oxides. The growth and fabrication conditions of these films significantly affect the performance of the fabricated photovoltaic devices. In the pioneering work of Burschka et al., they have applied a sequential solution deposition protocol to deposit a thin film of PbI2 into ∼350 nm thick mesoporous TiO2, followed by an appropriate dipping in a CH3NH3I/isopropanol solution for perovskite conversion. The small crystallite size of PbI2 deposited in the mesoporous TiO2 host matrix allows remarkable perovskite conversion upon diffusion of CH3NH3I. The complete conversion of crystalline perovskite was notably obtained within a few seconds. They monitored the perovskite formation integrally by optical. We demonstrate the use of nanoplasmonic sensing (NPS) to detect the formation kinetics of CH3NH3PbI3 perovskite at the interface of up to ∼650 nm compact/mesoporous TiO2 films with Au nanodisks. We assess the formed materials at the interface according to analytical results obtained by NPS and other characterization techniques
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