Metal halide perovskite solar cells (PSCs) are infamous for their batch‐to‐batch and lab‐to‐lab irreproducibility in terms of stability and performance. Reproducible fabrication of PSCs is a critical ...requirement for market viability and practical commercialization. PSC irreproducibility plagues all levels of the community; from institutional research laboratories, start‐up companies, to large established corporations. In this work, the critical function of atmospheric humidity to regulate the crystallization and stabilization of formamidinium lead triiodide (FAPbI3) perovskites is unraveled. It is demonstrated that the humidity content during processing induces profound variations in perovskite stoichiometry, thermodynamic stability, and optoelectronic quality. Almost counterintuitively, it is shown that the presence of humidity is perhaps indispensable to reproduce phase‐stable and efficient FAPbI3‐based PSCs.
Atmospheric humidity control during the fabrication process crucially influences the phase formation and stability of formamidinium perovskites. This work reveals that controlled humidity during the fabrication process is a key to achieving reproducible fabrication of high‐quality and stable perovskite films. Thus, precise humidity management is essential to ensure the reproducible, efficient, and stable perovskite solar cells.
Solar cells are semiconductor devices that generate electricity through charge generation upon illumination. For optimal device efficiency, the photogenerated carriers must reach the electrical ...contact layers before they recombine. A deep understanding of the recombination process and transport behavior is essential to design better devices. Halide perovskite solar cells are commonly made of a polycrystalline absorber layer, but there is no consensus on the nature and role of grain boundaries. This review concerns theoretical approaches for the investigation of extended defects. We introduce recent computational studies on grain boundaries, and their influence on point-defect distributions, in halide perovskite solar cells. We conclude with a discussion of future research directions.
We investigated the stability and the electronic structure of mixed halide perovskite including CsPb(I1−xBrx)3 and CsPbBr1−xClx3. To model mixed halide perovskites, random structures were generated, ...and relaxed at the generalized gradient approximation (GGA) level calculation with van der Waals correction. The stability of alloys was discussed in terms of the mixing enthalpy. The electronic band gap of alloys was obtained by using both GGA and hybrid density functional. The hybrid density functional theory calculation shows better agreement with the experimental band gap. We also found that the electronic band gap can be obtained cost-effectively by using a reduced k-point grid for the Fock exchange potential.
Display omitted
•In PBE + vdW calculation, cesium lead halides favored the orthorhombic phase.•GGA underestimate the band gap of alloy but can be resolved by using the hybrid DFT.•Band gap calculation by using downsampled k-point grids for the exact exchange.
Display omitted
•UV-curable different-colored 3Y-ZrO2 resins with 50 vol% of ceramic were prepared.•Photocurability, viscosity, flowability, and printability were investigated.•Flexural strength was ...comparable to that of conventionally manufactured resins.•Multilayered objects were continuously 3D printed and simultaneously sintered.•The different-colored sintered bodies exhibited a high relative density (>99.90%).•The all sintered bodies exhibited a high flexural strength (>930 MPa).
UV-curable different-colored 3Y-ZrO2 ceramic nanocomposite resins with a ceramic content of 50 vol% were prepared for supportless stereolithography 3D printing. Based on the correlation between the solubility parameters of UV-curable organic resin systems and the rheological behaviors of highly loaded ceramic nanocomposites, the physical properties of the different-colored 3Y-ZrO2 ceramic nanocomposite resins, such as photocurability, viscosity, flowability, and printability, were optimized for a supportless 3D printing process. Thus, white, pink, yellow, and gray 3Y-ZrO2 ceramic nanocomposite resins with optimum physical properties were prepared. The different-colored 3D-printed 3Y-ZrO2 objects sintered at 1450 °C for 180 min exhibited a high relative density of>99.90% and a high flexural strength of>930 MPa, which are comparable to those of commercial 3Y-ZrO2 manufactured by a conventional ceramic process. In addition, gear-shaped objects with different-colored layers of ceramic resins were successfully manufactured by continuous 3D printing and simultaneous sintering. This study paves the way for innovation in the manufacturing of ceramic products by 3D printing as an alternative to the traditional ceramic process.
The behavior of grain boundaries in polycrystalline halide perovskite solar cells remains poorly understood. Whereas theoretical studies indicate that grain boundaries are not active for ...electron–hole recombination, there have been observations of higher nonradiative recombination rates involving these extended defects. We find that iodine interstitial defects, which have been established as a recombination center in bulk crystals, tend to segregate at planar defects in CsPbI3. First-principles calculations show that enhanced structural relaxation of the defects at grain boundaries results in increased stability (higher concentration) and deeper trap states (faster recombination). We show how the grain boundary can be partly passivated by halide mixing or extrinsic doping, which replaces or suppresses the formation of trap states close to the grain boundaries.
Using first-principles density functional calculations, we investigate the relative stability and electronic structure of the grain boundaries (GBs) in zinc-blende CdTe. Among the low-Σ-value ...symmetric tilt Σ3 (111), Σ3 (112), Σ5 (120), and Σ5 (130) GBs, we show that the Σ3 (111) GB is always the most stable due to the absence of dangling bonds and wrong bonds. The Σ5 (120) GBs, however, are shown to be more stable than the Σ3 (112) GBs, even though the former has a higher Σ value, and the latter is often used as a model system to study GB effects in zinc-blende semiconductors. Moreover, we find that although containing wrong bonds, the Σ5 (120) GBs are electrically benign due to the short wrong bond lengths, and thus are not as harmful as the Σ3 (112) GBs also having wrong bonds but with longer bond lengths.
PDF
