The power conversion efficiency of lead halide perovskite solar cells has been elevated to 25.2%. However, the toxicity of lead and the complex fabrication process of those cells considerably hinder the commercial application of such solar cells. Therefore, lead-free solar cells with comparable power conversion efficiency with a much lower environmental impact have recently attracted enormous attention in both academia and industry. This paper presents a theoretical study to assess the energy conversion capacity of lead-free perovskite solar cells with MASnI3 perovskite as its absorber layer using solar cell capacitance simulator (SCAPS). In particular, the effects of materials of the perovskite solar cells’ electron transport layers (ETLs) and hole transport layers (HTLs) on their energy conversion performance are elaborated. Our results show that Cd0.5Zn0.5S and MASnBr3 are the most suitable materials for ETL and HTL, respectively. It is also found from that the solar cell performance can be further enhanced through optimizing the thickness and defect density of its absorber layer. Moreover, the effects of defect densities in interface layers are investigated. In addition, the effects of ETL and HTL doping densities as well as influences of the back-contact work function and operating temperature of the tin-based perovskite solar cells are discussed. Finally, a glass substrate/FTO/Cd0.5Zn0.5S (ETL)/MASnI3/MASnBr3 (HTL)/back-contact solar cell with a power conversion efficiency of 23.86% is recommended for further optimization.

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To avoid environmental pollution caused by lead, the tin-based perovskite solar cells have become a research hotspot in the photovoltaic field. Numerical simulations of tin-based perovskite solar cells are conducted by the solar cell simulation software, SCAPS-1D, with different electron transport layers and hole transport layers. And then the performances of perovskite solar cells are compared with each other and analyzed on different carrier transport layers. The results show that band alignment between the carrier transport layer and the perovskite layer are critical to cell performances. A higher conduction band or electronic quasi-Fermi level of electron transport layer can lead to a higher open circuit voltage. Similarly, a lower valence band or hole quasi-Fermi level of hole transport layer can also promote a higher open circuit voltage. In addition, when the conduction band of electron transport layer is higher than that of the absorber, a spike barrier is formed at the interface between the electron transport layer and perovskite layer. Nevertheless, a spike barrier is formed at the interface between the perovskite layer and the hole transport layer if the valence band of hole transport layer is lower than that of the absorber. However, if the conduction band of electron transport layer is lower than that of the absorber or the valence band of hole transport layer is higher than that of the absorber, a cliff barrier is formed. Although the transport of carrier is hindered by spike barrier compared with cliff barrier, the activation energy for carrier recombination becomes lower than the bandgap of the perovskite layer, leading to the weaker interface recombination and the better performance. Comparing with other materials, satisfying output parameters are obtained when Cd_0.5Zn_0.5S and MASnBr₃ are adopted as the electron transport layer and the hole transport layer, respectively. The better performances are obtained as follows: <i>V</i>_oc = 0.94 V, <i>J</i>_sc = 30.35 mA/cm², FF = 76.65%, and PCE = 21.55%, so Cd_0.5Zn_0.5S and MASnBr₃ are suitable carrier transport layer materials. Our researches can help to design the high-performance tin-based perovskite solar cells.

In this paper, a recently proposed micromechanical model for concrete is combined with a simple lattice model to simulate the behaviours of plain concrete specimens under tension, compression and three-point bending. The Mori–Tanaka method based micromechanical model for concrete considers the microcracks around the mortar–coarse aggregate interface and the aligned coalesced cracks in the concrete. It explicitly correlates the mechanical properties of concrete with the properties of its constituents such as mortar and coarse aggregates. The adopted simple lattice model, in which the axial interaction between neighbouring points is considered as a truss, does not need to generate grain structure and is thus easy to implement. Hence, this combination can be used to investigate the influences of the concrete constituents' properties on the behaviours of the concrete specimens in a simple way. The predicted deformation responses and crack patterns from the computational model are generally in agreement with the experimental observations.

This paper studies the existence and uniqueness of local strong solutions to an Oldroyd-B model with density-dependent viscosity in a bounded domain d Ω ⊂  , 2 d = or 3, via incompressible limit, in which the initial data is "well-prepared" and the velocity field enjoys the slip boundary conditions. The main idea is to derive the uniform energy estimates for nonlinear systems and corresponding incompressible limit.