Nanomechanical Approach for Flexibility of Organic–Inorganic Hybrid Perovskite Solar Cells

Abstract

The mechanical flexibility of perovskite solar cells as well as high power conversion efficiency is attracting increasing attention. In addition to existing empirical approaches, such as cyclic bending tests, in this study we report the tensile properties of the perovskite materials themselves. Measuring the tensile properties of free-standing perovskite materials is critical because (1) tensile properties represent the realistic mechanical properties of the film-type perovskite layer in the solar cells including the effects of various defects, and (2) deformation behavior of the perovskite layer at any deformed state of the solar cells can be analyzed using solid mechanics with the tensile properties as input. Critical bending radius of MAPbI 3 -based flexible solar cells is found to be between 0.5 and 1.0 mm by the decrease in power conversion efficiency during cyclic bending deformation. This finding agrees well with the critical bending radius of 0.66 mm determined based on the elastic deformation limit of 1.17% for MAPbI 3 found by in situ tensile testing. Scanning electron microscopy observations and hole-nanoindentation tests suggest that the formation of coarse cracks in the perovskite layers is the primary cause of the decrease in power conversion efficiency observed in flexible perovskite solar cells.

Toward Highly Thermal Stable Perovskite Solar Cells by Rational Design of Interfacial Layer

“…In addition, these results imply a threshold fracture stress of between 160 and 280 MPa. This value is consistent on the order of magnitude with the previous reported yield stress (∼740 MPa for single crystal perovskite), and tensile fracture stress (∼130 MPa for polycrystal perovskite film) of MAPbI 3 perovskite, indicating good validity of this simulation (Reyes-Martinez et al., 2017, Ahn et al., 2019). In a word, the mechanics simulation suggests significant mechanical buffer effect of the thick and soft interfacial layer, providing reasonable explanation for the alleviated wrinkles of PEDOT:PSS-based perovskite film.

Figure 4Mechanics Simulation(A) Dependence of max Tresca equivalent stress on the modulus and thickness of interfacial layer under a simulative temperature of 120°C.(B) Dependence of radius of curvature on the modulus of interfacial layer under a simulative temperature of 120°C.

…”

Flexible, All‐Inorganic CsPbBr3 Perovskite Solar Cells Tailored by Heat‐resistant Muscovite Substrates

“…As a result, the maximum EPS increases to 0.221 % (Figure 3c), which is similar to the case of the convex bending. This value is lower than the tensile‐elastic deformation limit of the hybrid perovskite, [30] partly explaining the origin of their excellent mechanical flexibility, which can be further cross‐checked by the unchanged surface morphologies of ITO, Sb‐TiO 2 and CsPbBr 3 films before and after bending tests (Figure 3d and Figure S13). Inspired by the FEA calculation, the precise control of carbon thickness to 2.7 μm (Figure S14) may minimize the strain of the CsPbBr 3 perovskite layer.…”

“…Note that the material parameters of CsPbBr 3 used here are measured on single crystal samples. Following this line of thought, Young's modulus of the polycrystalline film should be lower than that of the single crystal, owing to grain boundaries [30] . Therefore, we reduce the Young's moduli to 10 and 5 GPa, which are comparable to those of the organic‐inorganic hybrid perovskite polycrystalline films [31] .…”

Two-dimensional ultrathin MoS2-modified black Ti3+–TiO2 nanotubes for enhanced photocatalytic water splitting hydrogen production

“…Fossil fuel exhaustion and environmental pollution have caused serious global concerns. Therefore, it is imperative to develop novel renewable sustainable and clean energy sources [1][2][3][4] such as solar cells, photovoltaic devices, hydrogen fuel cells, and bioenergy devices [5][6][7][8] . Owing to their solar independence and high unit capacity, hydrogen fuel cells are considered to be the most efficient renewable energy sources [ 9 , 10 ].…”