Abstract
Perovskite Solar Cells (PSC), with the efficiency of more than 22%, has shown promising prospects for the future of environmentally friendly technology. However, low stability on humidity is a major problem limiting the commercialization of PSC. The perovskite material commonly used as a perovskite solar-cell active material is methylammonium lead tri-iodide (CH3NH3PbI3 or MAPbI3) prepared with a mixture of methylammonium-iodide (MAI) and lead iodide (PbI2). Perovskite material MAPbI3 is hygroscopic and easily decomposed into its constituent material, thereby reducing the performance of the PSC. Meanwhile, perovskite methylammonium lead-bromide (MAPbBr3) has higher moisture stability than MAPbI3 because it has a cubic crystal structure that has high symmetry. However, the efficiency of solar cells using MAPbBr3 as active material is lower than that of MAPbI3, due to a higher bandgap (~2.2 eV) than that of MAPbI3 (~1.5 eV). Therefore the wavelength range of sunlight absorbed by MAPbBr3 is shorter. We have studied the effect of the ratio of Bromium ion (Br-) insertion into MAPbI3 perovskite, forming mixed perovskite halide MAPbBrxI3-x on the stability of thin perovskite films in ambient with air humidity 70%. The value of x is varied from x = 0, 0.25, 0.5, 0.75 and 3. We measured the evolution of UV-Vis spectra and XRD patterns of thin perovskite films. The MAPbBr3 perovskite film is the most stable in high air relative humidity (> 70%). While mixed perovskite films with x = 0.5 are more stable as compared to the other x values based on absorption spectra. The XRD results showed that the stability of mixed halide perovskite is decreased with the increasing of x value.
Highlights
Perovskite solar cells have been developing very rapidly and have been able to produce power conversion efficiency (PCE) above 22% since it first developed in 2009 with PCE 3.9% [1,2]
We evaluated the changes of UV-Vis peak absorption of thin films and the changes of X-Ray Diffraction (XRD) main peak of thin films to observe the impact of Bromium ion (Br-)ion insertion on the stability of mixed perovskite films against humidity
The XRD measurements were done every 24 hours from just prepared to 48 hours after thin film preparation. Those UV-Vis and XRD measurements were performed to study the effect of Br-ion insertion on the stability of mixed perovskite films against humidity
Summary
Perovskite solar cells have been developing very rapidly and have been able to produce power conversion efficiency (PCE) above 22% since it first developed in 2009 with PCE 3.9% [1,2]. The most commonly used perovskite material for solar cells is methylammonium lead triiodide CH3NH3PbI3 or MAPbI3. This is because MAPbI3 has a bandgap of around 1.50 eV and has a range of light absorption ranging from the ultra-violet to near-infrared (800 nm) [4]. Perovskite material MAPbI3 has three crystalline structures/phases that are stable at different temperatures, namely orthorhombic, tetragonal, and cubic [11]. We evaluated the changes of UV-Vis peak absorption of thin films and the changes of XRD main peak of thin films to observe the impact of Br-ion insertion on the stability of mixed perovskite films against humidity
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