New Integration Approaches for Highly Arrayed Nanostructures for Organic/Inorganic Solar Cells

When metal nanoparticles (NP), such as silver (Ag) and gold (Au), are irradiated by sunlight, their localized surface plasmon is excited, thus causing light scattering and light absorption. The ratio of light absorption to scattering strongly depends on the particle size. In general, when the nanoparticles are larger than 100 nm in diameter, the extinction of light is dominated by scattering; this property is applied to anti-reflection or light trapping for solar cells. When the metal nanoparticles are smaller than several tens of nanometers, light extinction is dominated by light absorption, and this light absorption generates near-field light accompanied by a strong electric field. In 1997, we previously introduced the concept of a dye-sensitized solar cell that utilizes localized surface plasmons and is thus called a “plasmonic DSSC” [1]. In this DSSC, near-field light is used to enhance both the photoabsorption of Ru-dye and the generation of photoelectrons. By introducing AgNPs into a film of N3 dye, the absorbance of the dye can be increased by a factor of 149. Absorption enhancement has also been reported when the composite films are formed with AuNPs and black dye (BD). A key factor for enhancing the photoabsorption of a plasmonic DSSC with such a composite film is an overlap in the photoabsorption spectra between the metal nanoparticles and the dye. [2] In this paper, we summarized our enhancements of DSSCs by using localized surface plasmon with focusing on the nanometer-distance control between metal NP, dyes and TiO2. Furthermore, the applications of localized surface plasmon to next generation of solar cells will be introduced. The types of solar cells suitable for applying localized surface plasmon will comprehensively be discussed. Plasmonic dye-sensitized solar cells DSSC with AgNPs showed improved photoelectric conversion efficiency (Eff ) of 2.5%, compared with about 1.5% for a DSSC without AgNPs [3]. In that study, to clarify the effect of AgNPs on the power generation characteristics, the TiO2 film of the DSSC was 2 μm thick, which is thinner than that for a typical DSSC (~10 μm). An optimal thickness of the TiO2 film should exist for capturing sunlight while preventing back charge transfer. The dependence of TiO2 thickness on the performance of a DSSC with metal nanoparticles had been investigated. [4] The level of electric field enhancement around AuNPs strongly depends on parameters such as the dielectric constant, distance from the surface of the particle, particle size, particle shape, and light wavelength, and thus depends on the combination of materials and their surface state. The length and conformation of the surface modulator is critical to determine the distance between the dyes, metal nanoparticles and TiO2. [5] Figure 1 shows the schematic of nanometer-distance control using a surface modulator in DSSC. Attempting to highly control the distance, the hybridization of the peptide nucleic acide (PNA), which has similar structure to deoxyribonucleic acid (DNA), was used to improve the efficiency of DSSC. The Eff of DSSC was enhanced from 3.1% to 4.0% by the incertion of Ag NP with PNA bonded with TiO2. [6] Applications of localized surface plasmon to next generation of solar cells The following applications of localized surface plasmon to several kinds of solar cell (Plasomonic unti-reflecting coating for silicon solar cells [7], Plasmonic extremely thin absorber (ETA) solar cells [8, 9], Plasmonic interlayer for multijunction solar cells [10], and Plasmonic porous silicon solar cells) will be sumarized. At same time, the suitable type of solar cells for the applying will be discussed with considering the principle of each solar cell. Finally, I will introduce the concept of silicon nanowire tandem solar cells under the project of “FUTURE-PV Innovation”. Acknowledgement A part of this work was supported by the MEXT, FUTURE－PV Innovation Project.

Progress in one-dimensional nanostructures

Diversifying Progress in Solar

Organic–inorganic perovskites have demonstrated an impressive potential for the design of the next generation of solar cells. Perovskite solar cells (PSCs) are currently considered for scaling up and commercialization. Many of the lab‐scale preparation methods are however difficult to scale up or are environmentally unfriendly. The highest efficient PSCs are currently prepared using the antisolvent method, which utilizes a significant amount of an organic solvent to induce perovskite crystallization in a thin film. An antisolvent‐free method is developed in this work using flash infrared annealing (FIRA) to prepare methylammonium lead iodide (MAPbI3) PSCs with a record stabilized power conversion efficiency of 18.3%. With an irradiation time of fewer than 2 s, FIRA enables the coating of glass and plastic substrates with pinhole‐free perovskite films that exhibit micrometer‐size crystalline domains. This work discusses the FIRA‐induced crystallization mechanism and unveils the main parameters controlling the film morphology. The replacement of the antisolvent method and the larger crystalline domains resulting from flash annealing make FIRA a highly promising method for the scale‐up of PSC manufacture.

The application of inverse titania opals in nanostructured solar cells

Lead-free perovskites have garnered significant attention as a promising alternative to traditional toxic Pb-containing materials in solar cells. Although lead-based perovskites have achieved high solar energy conversion efficiencies (>25%), their contamination and environmental risks limit their commercial application. Materials based on tin (Sn), bismuth (Bi), antimony (Sb), and germanium (Ge) exhibit the potential to replace lead-based perovskites due to their similar optical and electrochemical properties and lower toxicity. However, key challenges remain, including their lower stability, susceptibility to oxidation (notably Sn2+), and reduced efficiency compared to Pb-based materials. This article reviews recent advancements in the synthesis of lead-free perovskites, methods for improving their structural and functional properties, and their prospects for application in solar cells. The presented review consolidates data on the photovoltaic efficiency, stability, durability, and environmental safety of lead-free perovskites. It discusses their future market potential, emphasizing their environmental friendliness, wide applicability in solar cells, light-emitting devices, neuromorphic systems for artificial intelligence, and microelectronics, as well as scalable production methods that have been developed. The need for further research to optimize their properties and scale up technologies for industrial applications is highlighted. The analysis demonstrates that lead-free perovskites hold substantial promise as a foundation for the next generation of solar cells, providing an environmentally clean and sustainable solution for renewable energy. Nonetheless, addressing the technological challenges related to their stability and scalability is critical for unlocking their full potential.

With the global demand for renewable energy sources, there is a race in the scientific community to build a highly efficient solar cell. Nanostructured solar cells are a class of photovoltaic devices which is a strong candidate for high efficiency energy generation. Hot carrier solar cells are a kind of nanostructured solar cells, for offering high power conversion efficiency, compared with the conventional single absorber solar cell, through the process of extracting power from photo-generated high energetic carriers prior to thermalization to lattice via phonons. In this paper, we have analyzed the band structure, thermodynamic properties, and hot carrier transport in solar cell.

Within the past several decades, photovoltaic technology is an emerging pioneer in the renewable energy field. Driven by the rapid decline in the price of photovoltaic products, the cost of photovoltaic power generation is becoming cheaper or even lower than the cost of thermal power generation. Among various photovoltaic technologies, organic-inorganic hybrid perovskite thin film solar cells are promising candidates for the next generation of solar cells in consideration of their outstanding advantages such as low-cost, easy manufacturing processing and high power conversion efficiencies. Perovskite solar cells stem from dye-sensitized solar cells. Within less than a decade of rigorous research and development in perovskite solar cells, the efficiency is boosted up to 25.2%. Aforementioned high PCE is mainly attributed to outstanding photovoltaic properties such as the long diffusion length of carriers, high optical absorption coefficient, excellent carrier mobility, etc. Meanwhile, the main barriers of commercialization for the perovskite solar cells are the poor stability of the devices, and the possible environmental pollution caused by lead. Herein, we briefly reviewed the opportunities and the challenges of this game changer in photovoltaic field. The development prospective are also discussed.

Recent technological advances in conventional planar and microstructured solar cell architectures have significantly boosted the efficiencies of these devices near the corresponding theoretical values. Nanomaterials and nanostructures have promising potential to push the theoretical limits of solar cell efficiency even higher using the intrinsic advantages associated with these materials, including efficient photon management, rapid charge transfer, and short charge collection distances. However, at present the efficiency of nanostructured solar cells remains lower than that of conventional solar devices due to the accompanying losses associated with the employment of nanomaterials. The concurrent design of both optical and electrical components will presumably be an imperative route toward breaking the present‐day limit of nanostructured solar cells. This review summarizes the losses in traditional solar cells, and then discusses recent advances in applications of nanotechnology to solar devices from both optical and electrical perspectives. Finally, a rule for nanostructured solar cells by concurrently engineering the optical and electrical design is devised. Following these guidelines should allow for exceeding the theoretical limit of solar cell efficiency soon.

Nanostructured solar cells have the potential to provide a low-cost alternative to more traditional thin film solar cell technologies. Of particular interest are nanostructured solar cells with inorganic semiconductor absorbers, due to their favorable absorption properties. Such devices include quantum-dot-sensitized solar cells (QDSSCs), extremely thin absorber solar cells (ETASCs), and colloidal quantum dot solar cells (CQDSCs). However, these device architectures suffer from high rates of internal recombination and other problems associated with their extensive internal surface areas. Interfacial surface treatments have proven to be a highly effective means to improve the electronic properties of these devices, leading to overall gains in efficiencies. In this Perspective, we focus on three types of interfacial modification: band alignment by molecular dipole layers, improved CQD film mobilities by ligand exchange, and reduced recombination by interfacial inorganic layers. Select examples in each of these categories are highlighted to provide a detailed look at the underlying mechanisms. We believe that surface modification studies in these devices-QDSSCs, ETASCs, and CQDSCs-are of interest not only to these fields, but also to the broader photovoltaics community.

Nanostructures in III–V solar cells have been widely investigated. Due to the enhancement in photon absorption, higher short-circuit current has been achieved in a number of previous reports. However, many of the nanostructured solar cells suffer from low open circuit voltage and low fill factor, which result from poor junction quality and high non-radiative recombination. Such problems can be resolved by utilizing both a nanostructured III–V window layer and planar p-n junction. In this work, we demonstrate the design and optimization of nanostructured window solar cells through a set of carefully designed experiments. A systematic study based on device fabrication, characterization and simulation is presented. This work shows that reducing absorption and minority carrier loss inside the nanostructured window are key to further improve the performance of nanostructured window solar cells.

Perovskite solar cell (PVSC), after its invention since 2009, has attracted tremendous attention from both academia and industry, because of its low cost, ease of manufacturing features and the sky-rocketing efficiencies being achieved within such a short period of time. Currently, the new efficiency record has reached 21.0%, comparable to that of the commercialized PV technologies developed for decades, such as multi-crystalline Si, CIGS and CdTe thin film solar cells. It is very possible that PVSCs would one day step over the threshold of marketization, share or even overturn the current PV market dominated by crystalline-Si solar cells. However, there are still several obstacles to be overcome on the road towards PVSC industrialization. This paper has reviewed the brief developing history and the current research status of PVSCs, and explained: Why PVSCs are so important in the next-generation solar cells, why organometal halide perovskites work so well as light absorbers, and what the inherent differences are among different cell configurations. The prospects on how to realize scale-up industrialization of PVSCs have also been given in the sequence of efficiency, stability, cost, toxicity, and short-term objectives. Resolutions to the remaining challenges according to their orders of technical difficulty and importance have also been discussed.

Chapter 2 - Advances in the large-scale production, fabrication, stability, and lifetime considerations of electronic materials for clean energy applications

Alternative deposition methods and materials are of interest for the fabrication of thin film solar cells since they offer potential enhancements for either low cost, high speed or high efficiency but also because they can help in better understanding the underlying physical and chemical processes that could lead to the next generation of solar cells. In this study, we will present new results on the deposition of ZnS by atomic layer deposition (ALD) as an alternate to CdS deposited by chemical bath deposition.

Perovskite solar cells (PSCs) are attracting much attention as the most promising candidate for the next generation of solar cells. This is due to their low cost and high power conversion efficiency in spite of their relatively short period of development. Key components of PSCs are a variety of halide perovskites with ABX3 stoichiometry, which are used as photoabsorbers. Their outstanding optoelectronic properties have brought breakthroughs in photovoltaic technology. To commercialize PSCs in the near future, however, these materials need to be further improved for better performance, represented by high efficiency and high stability. As in other materials development, atomistic modelling and simulation can play a significant role in finding new functional halide perovskites as well as revealing the underlying mechanisms of their material processes and properties. In this sense, computational work on the halide perovskites, mostly focusing on first-principles works, are reviewed with an eye to looking for ways to improve the performance of PSCs. Specific modelling and simulation techniques to quantify material properties of the halide perovskites are also presented. Finally, the outlook for the challenges and future research directions in this field is provided.