Chlorine activated stacking fault removal mechanism in thin film CdTe solar cells: the missing piece

Metal Clusters Based Multifunctional Materials for Solar Cells

As a multifunctional material, metal clusters have recently received some attention for their application in solar cells.This review delves into the multifaceted role of metal clusters in advancing solar cell technologies, covering diverse aspects from electron transport and interface modification to serving as molecular precursors for inorganic materials and acting as photosensitizers in metal-cluster sensitized solar cells (MCSSCs). The studies conducted by various researchers illustrate the crucial impact of metal clusters, such as gold nanoclusters (Au NCs), on enhancing solar cell efficiency through size-dependent effects, distinct interface behaviors, and tailored interface engineering. From optimizing charge transfer rates to improving light absorption and reducing carrier recombination, metal clusters prove instrumental in shaping the landscape of solar energy conversion.The promising performance of metal-cluster sensitized solar cells, coupled with their scalability and flexibility, positions them as a exciting avenue for future clean energy applications. The article concludes by emphasizing the need for continued interdisciplinary research and technological innovation to unlock the full potential of metal clusters in contributing to sustainable and high-performance solar cells.

The Electrical Behaviors of Grain Boundaries in Polycrystalline Optoelectronic Materials

Polycrystalline optoelectronic materials are widely used for photoelectric signal conversion and energy harvesting and play an irreplaceable role in the semiconductor field. As an important factor in determining the optoelectronic properties of polycrystalline materials, grain boundaries (GBs) are the focus of research. Particular emphases are placed on the generation and height of GB barriers, how carriers move at GBs, whether GBs act as carrier transport channels or recombination sites, and how to change the device performance by altering the electrical behaviors of GBs. This review introduces the evolution of GB theory and experimental observation history, classifies GB electrical behaviors from the perspective of carrier dynamics, and summarizes carrier transport state under external conditions such as bias and illumination and the related band bending. Then the carrier scattering at GBs and the electrical differences between GBs and twin boundaries are discussed. Last, the review describes how the electrical behaviors of GBs can be influenced and modified by treatments such as passivation or by consciously adjusting the distribution of grain boundary elements. By studying the carrier dynamics and the relevant electrical behaviors of GBs in polycrystalline materials, researchers can develop optoelectronics with higher performance.

Arsenic doping and diffusion in CdTe: a DFT study of bulk and grain boundaries

The doping of CdTe with As is a method which is thought to increase cell efficiency by increasing electron hole concentrations. This doping relies on the diffusion of As through CdTe resulting in As_Tesubstitution. The potential effectiveness of this is considered through kinetic and electronic properties calculations in both bulk and Σ3 and Σ9 grain boundaries using Density Functional Theory. In bulk zinc-blende CdTe, isolated As diffuses with barriers <0.5 eV and with similar barriers through wurtzite structured CdTe, generated by stacking faults, suggesting that As will not be trapped at the stacking faults and hence the transport of isolated As will be unhindered in bulk CdTe. Substitutional arsenic in bulk CdTe has little effect on the band gap except when it is positively charged in the AX-centre position or occurring as a di-interstitial. However in contrast to the case of chlorine, arsenic present in the grain boundaries introduces defect states into the band gap. This suggests that a doping strategy whereby the grain boundaries are first saturated with chlorine, before single arsenic atoms are introduced, might be more beneficial.

Strain and thickness effects on the electronic structures of low-energy two-dimensional CdxTey phases

Cadmium telluride (CdTe) has prime importance in photovoltaics due to its direct band gap of 1.45 eV. However, its two-dimensional counterparts have not been fully explored due to polymorphism. We investigated the energy phase diagram of 2D Cd_xTe_y (x + y ≤ 8) using state-of-art computational methods and found the phases of CdTe and CdTe₂ on and near the energy convex-hull, respectively. Further screening of phonon and ab initio molecular dynamics simulations confirms their experimental viability. These structures reveal promising electronic properties. 2D CdTe has a robust direct band gap unaffected by thickness, monolayer to trilayer and bulk, and strain as high as ±7%. Such robust semiconductors are crucial for device applications because of challenges in the growth of wafer-scale uniform monolayers. In contrast, the direct band gap of 2D transition metal dichalcogenides is highly sensitive to thickness and strain, limiting their usage in devices. The 2D CdTe₂ has an indirect band gap whose magnitude is tunable by strain. The robust direct band gap of 2D CdTe and the tunable indirect band gap of CdTe₂ make them potential candidates for optoelectronic devices.

Synthesis and Characterization of High-Efficiency Halide Perovskite Nanomaterials for Light-Absorbing Applications

Inorganic perovskite materials are possible candidates for conversion of solar energy to electrical energy due to their high absorption coefficient. Perovskite solar cells (PSCs) introduced a new type of device structure that has attention due to better efficiencies and interest in PSCs that has been increasing in recent years. Halide perovskite materials such as CsPbIBr₂ show remarkable optical and structural performance with their better physical properties. Perovskite solar cells are a possible candidate to replace conventional silicon solar panels. In the present study, CsPbIBr₂ perovskite materials' thin films were prepared for light-absorbing application. Five thin films were deposited on the glass substrates by subsequent spin-coating of CsI and PbBr₂ solutions, subsequently annealed at different temperature values (as-deposited, 100, 150, 200 and 250 °C) to get CsPbIBr₂ thin films with a better crystal structure. Structural characterizations were made by using X-ray diffraction. CsPbIBr₂ thin films were found to be polycrystalline in nature. With increasing annealing temperature, the crystallinity was improved, and the crystalline size was increased. Optical properties were studied by using transmission data, and by increasing annealing temperature, a small variation in optical band gap energy was observed in the range of 1.70-1.83 eV. The conductivity of CsPbIBr₂ thin films was determined by a hot probe technique and was found to have little fluctuating response toward p-type conductivity, which may be due to intrinsic defects or presence of CsI phase, but a stable intrinsic nature was observed. The obtained physical properties of CsPbIBr₂ thin films suggest them as a suitable candidate as a light-harvesting layer. These thin films could be an especially good partner with Si or other lower band gap energy materials in tandem solar cells (TSC). CsPbIBr₂ material will harvest light having energy of ∼1.7 eV or higher, while a lower energy part of the solar spectrum will be absorbed in the partner part of the TSC.