Layer Material For Solar Cells Research Articles

Solar Cell Application of 1D Heterostructure Based on Single-Walled CNT

The experimental synthesis of one-dimensional (1D) van der Waals heterostructures, first introduced in 2020 [1], has attracted much research attention. Discussions upon this coaxial stack of different atomic layers are not only limited to synthesis and characteristics, but also extended to applications. Many unique properties of the 1D van der Waals heterostructures, such as the adjustable band gap, strong quenching of photoluminescence of MoS2 by inner single-walled CNT, enable this structure to be a potential active layer material for solar cells [2].For the synthesis of 1D van der Waals heterostructures, we first use dispersed high-purity semiconducting single-walled carbon nanotubes (s-SWCNT) solution obtained from Kataura group [3] as inner tube material. With an anodic aluminum oxide (AAO) membrane filter and HCl, we managed to fabricate a free-standing s-SWCNT film [4]. Then following our established CVD process [5], we are wrapping this inner s-SWCNT tube with an insulating boron nitride layer, and a semiconducting MoS2 layer. After that, the as-prepared 1D van der Waals heterostructures film will be utilized for solar cell fabrication.The solar cell is adopting an n-i-p structure, in the order of glass-ITO-SnO2-Active layer-Spiro-Au. After spin-coating and annealing SnO2 (electron transporting layer) onto ITO-patterned glass, the 1D van der Waals heterostructure film is laminated on the SnO2 layer. Spiro (hole transporting layer) will be then spin-coated onto the film. Finally, gold is vapor-deposited onto the device in a vacuum chamber, as the top electrode [6].Through photocurrent measurement of 1D van der Waals structure film using Esko film, a mixture of metallic-SWCNT and s-SWCNT, we found it is photosensitive with exposure to light and laser. The 1D van der Waals structure film using high-purity s-SWCNT is then expected to generate higher photocurrent, the experimental result will be updated in the future. By the IV measurement of the solar cell, we observed the photovoltaic effect of the device. Moreover, this new conceptual solar cell is believed to possess many advantages at the same time, such as flexibility, durability, non-toxicity, and sustainability [2]. However, further research on the choices of materials and optimizations of device parameters is still required in order to reach sufficient power conversion efficiency as a photovoltaic device.[1] R. Xiang et al., Science 367, 537–542 (2020)[2] R. Xiang et al., Natl Sci Open 1, 3 (2022)[3] J. Cui et al., ACS Appl. Nano Mater 2, 1, 343–350 (2019)[4] C. Zhang et al., ACS Nano 16, 11, 18630–18636 (2022)[5] M. Liu et al., ACS Nano 15, 5, 8418–8426 (2021)[6] J.-M. Choi et al, Adv. Funct. Mater. 32, 2204594 (2022)

Dimension-dependent intrinsic point defect characteristics of binary photovoltaic materials

Because the absorption layer materials in solar cells have different dimensions, they have different material properties. Defect formation energy can increase with the increase of material dimensions.

Simulation analysis of Cd-free Cu(In,Ga)Se2 solar cells with novel BiOX (X=Cl, Br) buffer layers

Nowadays, cadmium sulfide (CdS) or zinc oxysulfide (Zn(O,S)) are the traditional buffer layer of Cu(In,Ga)Se2 (CIGS) solar cells. However, these buffer layers contain several disadvantages, such as the complicated synthesis problem and heavy metal toxicity. To solve the above problems, the potential of Bi-based (BiOX: X = Cl, Br) materials employed as buffer layers for efficient CIGS solar cells are investigated by using SCAPS simulation software in this contribution. It can be found that all BiOX materials fabricated from a soft liquid deposition process possess 2D nanosheet structures. A comparison of 2D nanosheet size reveals that BiOBr can form easily compared with BiOCl under the same growth conditions. Simultaneously, DRS and XPS determine the energy band distribution of BiOX materials. Further investigations on the simulated device performance suggest that conversion efficiency of the BiOBr sample is maximum, which is close to that of CdS and much larger than the BiOCl sample, mostly owning to the increased JSC and FF. The reason for this results is that the energy band distribution of BiOBr is similar to that of CdS buffer layer. It also indicates that BiOBr has the potential to serve as a buffer layer material for solar cells.

An ab-initio investigation of novel double halide perovskite Cs2InCoX6(X=F, Cl, Br) materials with direct band structure and broadband light absorption

In this paper, the electronic, mechanical and optical properties of Cs2InCoX6(X = F, Cl, Br) have been studied by first-principle calculation method. The results show that both Cs2InCoCl6 and Cs2InCoBr6 are brittle while Cs2InCoF6 tends to be ductile. Cs2InCoF6, Cs2InCoCl6 and Cs2InCoBr6 are direct bandgap semiconductors with bandgap values of 3.002eV, 1.129eV and 0.865eV, respectively. Compared with other commonly used perovskite materials, Cs2InCoX6(X = F, Cl, Br) material has lower effective mass, which is beneficial to improve carrier transport and photoelectric device performance. In addition, Cs2InCoF6 is more suitable as photodetector and photocatalyst, and the absorption curves of Cs2InCoCl6 and Cs2InCoBr6 are well matched with the spectral irradiance of AM1.5. Because Cs2InCoCl6 has a more suitable band gap, it is a potential candidate for absorbing layer materials in solar cells.

Quantum yield enhancement of Mn-doped CsPbCl3 perovskite nanocrystals as luminescent down-shifting layer for CIGS solar cells

The emission and absorption properties of Mn doped CsPbCl3 NC make it ideal candidates as luminescent down shifting layer material for solar cells, However, effective Mn doping and further quantum yield improvement remains challenging. We present our modified hot injection route to obtain Mn doped CsPbCl3 nanocrystals with different morphologies and enhanced quantum yield. The samples presented were synthesized with precursor MnCl2 and PbCl2 with the ratio of 1:1, 1:2, 1:2.5 and 1:3. For samples with lower Mn doping level, the as prepared samples are uniform nanocubes with average size of 11 nm. When MnCl2 amount is increased beyond 2.5, large piece of nanosheets were found by TEM and AFM with ultrathin thickness and strong quantum confinement effect. CsPbCl3 nanocrystals with optimal Mn doping level show enhanced quantum yield of 69%. Luminescent down shifting layers prepared from Mn doped CsPbCl3 nanocrystals successfully increased short-circuit current (6.67%) and PCE (1.67%) of Cu(In,Ga)Se2 solar cell.

Study on the Property of Electron-Transport Layer in the Doped Formamidinium Lead Iodide Perovskite Based on DFT.

The electron-transport layer in planar perovskite solar cells plays an important role in improving photoelectric conversion efficiency. At present, the main electronic transmission materials in perovskite solar cells include TiO2, ZnO, WO3, ZrO2, SnO2, ZnO2, etc. This work mainly studies the electron-transport characteristics of six different electron-transport layers in perovskite solar cells. Based on the density functional theory, the electron-transport model of a solar cell doped with formamidinium iodide lead compound perovskite under six different electron-transport materials was constructed, and their effective electron mass and the mobility of carriers were obtained by optimizing the structure and theoretical calculation. The results show that the mobility of electrons in TiO2 crystal is slightly higher than that of FA0.75Cs0.25Sn0.5Pb0.5I3 carriers. Because of their high matching degree, it can be reasonably explained that titanium dioxide has been widely used in perovskite solar cells and achieved higher photoelectric conversion efficiency. In addition, the mobility of carriers in WO3 and SnO2 crystals is also high, so they also have great advantages in carrier transport. Due to its abundant, nontoxic, and low-pollution content, TiO2 has become the most widely used electronic transmission layer material for solar cells. Furthermore, we have explored eight new semiconductor materials that have not yet been used in perovskite solar cells as the electron-transport layer. The calculation results show that Ta2O5 and Bi2O3 are promising materials for the electron-transport layer. This study provides a theoretical basis for seeking better electronic transmission materials for solar cells in the future.

Investigation of microstructural and optical properties of (K,Ba)(Ni,Nb)O3−δ thin films fabricated by pulsed laser deposition

Perovskite-type ferroelectrics are increasingly being studied for applications in solar-energy conversion because of their efficient ferroelectric polarization-driven carrier separation and above-bandgap generated photovoltages. (K,Ba)(Ni,Nb)O3−δ ferroelectric films, a highly promising and low-cost absorber layer material for solar cells, have been fabricated on Pt(111)/Ti/SiO2/Si(100) substrates for the first time, using a modified pulsed laser deposition method. Well-crystallized near-stoichiometric (K,Ba)(Ni,Nb)O3−δ film was obtained by adjusting the target–substrate distance to 50mm and setting the substrate at an oblique angle of ~11° from the plume axis. Microstructural characterizations show the as-grown film exhibits a single-phase perovskite structure with a dense and uniform surface. The optical absorption spectrum of (K,Ba)(Ni,Nb)O3−δ has two main peaks, i.e., a significant peak at the intermediate energy adjacent to a much larger peak at higher photon energy, which indicates intraband multiple electronic transition. The present results could be crucial for potential solar-energy device applications.

Quaternized Pyridyloxy Phthalocyanines Render Aqueous Electron‐Donor Carbon Nanotubes as Unprecedented Supramolecular Materials for Energy Conversion

Exploring new properties in known materials, sometimes even achieving behaviors opposite to those traditionally encountered, is a fundamental aspect of innovation in materials science. In the field of energy conversion, for example, the development of water‐processed organic solar cells provides environmentally friendlier materials, which contribute to reduce health risks. Herein, a novel approach is described to produce water‐soluble electron‐donor single wall carbon nanotube (SWCNT) hybrids based on the noncovalent immobilization of quaternized pyridyloxy zinc phthalocyanines (ZnPc) with a varying number of pyridyl substituents. Moreover, the excellent electron‐accepting ability of the latter ZnPcs is reported. The introduction of tert‐butylphenyl groups at the pyridines enables for the first time a complete characterization. The electron‐acceptor nature of the ZnPcs enables switching the role of SWCNTs within the resulting supramolecular hybrids. Finally, a proof‐of‐concept demonstration of the SWCNT/ZnPc hybrids' capacity for energy conversion is presented, paving their way to possible use as active layer material in solar cells processed entirely from aqueous solutions.

Enhancing the power conversion efficiency of PCDTBT:PC71BM polymer solar cells using a mixture of solvents

Organic polymer solar materials are shown to exhibit better solubility in mixed solvents than in pure ones, which affects the performance of their solar cells. In this article, poly[N-9-hepta-decanyl-2,7-carbazole-alt-5,5-(4,7-di-2-thienyl-2,1,3-benzothiadiazole) (PCDTBT) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) are used as active layer materials in solar cells. To optimize the performance of these active materials, the ratio of chloroform (CF) to chlorobenzene used as solvents to dissolve PCDTBT, and PC71BM is varied, which is shown to affect power conversion efficiency (PCE). The solar cell that shows the best performance with a PCE as high as 6.82 % is produced using a volume ratio of CF to chlorobenzene of 1:1.

Photochemical Deposition of GaSxOy Thin Films from Aqueous Solutions

Photochemical deposition (PCD) is a technique of film preparation from solutions by UV light illumination. In this study, GaSxOy thin films were prepared on fluorine-doped-tin-oxide-coated glass substrates by PCD from an aqueous solution of Ga2(SO4)3 and Na2S2O3. GaSxOy is a wide-band-gap semiconductor and suitable as a buffer layer material in solar cells. The as-deposited films were characterized by Auger electron spectroscopy, scanning electron microscopy and optical transmission spectroscopy. The O/Ga ratio was close to the stoichiometric ratio, 1.5, and the S/Ga ratio is much smaller, less than 0.3 for a film deposited under the optimum conditions. The film exhibited a wide energy band gap of 3.5 eV and a resistivity of the order of 102 Ω cm.

Physico-chemical characterisation of Cu(In,Al)Se 2 thin film for solar cells obtained by a selenisation process

Cu(In,Al)Se 2 thin films are investigated for their application as absorber layer material for solar cells. Films are elaborated by selenisation of multilayer metallic precursors deposited by thermal evaporation. In order to minimize the oxidation of the aluminium during the precursor deposition, an alternative deposition method using a Cu–Al eutectic is used. Films are characterized by X-ray diffraction, electron probe microanalysis, scanning electron microscopy, and optical measurements. These measurements show that most of the films are crystallized in the chalcopyrite structure and have the expected optical properties and composition. In some cases, the aluminium segregates and the films behave like CuInSe 2. In all cases, the films are not oxidized (less than 1 at.% of O 2).