Accelerated Thermal-Aging-Induced Degradation of Organometal Triiodide Perovskite on ZnO Nanostructures and Its Effect on Hybrid Photovoltaic Devices

Abstract

Organometal halide perovskite materials are presently some of the pacesetters for light harvesting in hybrid photovoltaic devices because of their excellent inherent electrical and optical properties. However, long-term durability of such perovskite materials remains a major bottleneck for their commercialization especially in countries with hot and humid climatic conditions, thus violating the international standards for photovoltaic technology. Albeit, TiO2 as an electron-transport layer has been well investigated for perovskite solar cells; the high-temperature processing makes it unsuitable for low-cost and large-scale roll-to-roll production of flexible photovoltaic devices. Herein, we have chosen low-temperature (<150 °C)-processable nanostructured ZnO as the electron-selective layer and used a two-step method for sensitizing ZnO nanorods with methylammonium lead iodide (MAPbI3) perovskite, which is viable for flexible photovoltaic devices. We have also elaborately addressed the effect of the annealing duration on the conversion of a precursor solution into the required perovskite phase on ZnO nanostructures. The investigations show that the presence of ZnO nanostructures accelerates the rate of degradation of MAPbI3 films under ambient annealing and thus requires proper optimization. The role of ZnO in enhancing the degradation kinetics of the perovskite layer has been investigated by X-ray photoelectron spectroscopy and a buffer layer passivation technique. The effect of the annealing duration of the MAPbI3 perovskite on the optical, morphological, and compositional behavior has been closely studied and correlated with the photovoltaic efficiency. The study captures the degradation behavior of the commercially interesting MAPbI3 perovskite on a ZnO electron-transport layer and thus can provide insight for developing alternative families of perovskite material with better thermal and environmental stability for application in low-cost flexible photovoltaic technology.

Impact of H2O on organic–inorganic hybrid perovskite solar cells

“…15). 123,124,139 Besides, another reason could be the more basic surfaces of ZnO compared with those of TiO 2 or ITO, which would facilitate protons to transfer and produce methylamine. 124,137 Also, an aqueous solution of ZnI 2 was proposed by Dkhissi et al to probably exist in this degradation.…”

Metal Oxides as Efficient Charge Transporters in Perovskite Solar Cells

“…[112] It was observed that the sputtering atmosphere had a crucial effect on the surface properties of the ZnO and, consequently, on the performance of the PSCs. [113] Several works on PSCs with ZnO as an ETM have reported the acute degradation of MAPbI 3 into PbI 2 upon annealing at even low temperatures, [114,115] which raises concerns about the suitability of ZnO in real world applications. [113] Several works on PSCs with ZnO as an ETM have reported the acute degradation of MAPbI 3 into PbI 2 upon annealing at even low temperatures, [114,115] which raises concerns about the suitability of ZnO in real world applications.…”

Recent progress in stabilizing hybrid perovskites for solar cell applications

“…2 Besides TiO 2 , ZnO may also react with perovskite under illumination and exacerbate the decomposition of the perovskite deposited on it [112] . A. Dhar et al [113] reported that the presence of ZnO accelerated the degradation rate of MAPbI 3 films under ambient annealing. Due to the relative basic nature of ZnO surface, proton-transfer reactions may happen at the ZnO/CH 3 NH 3 PbI 3 interface, leading to the de-protonation of the methylammonium cation.…”