Toward Eco-Friendly Dye-Sensitized Solar Cells (DSSCs): Natural Dyes and Aqueous Electrolytes

Due to their low cost, facile fabrication, and high-power conversion efficiency (PCE), dye-sensitized solar cells (DSSCs) have attracted much attention. Ruthenium (Ru) complex dyes and organic solvent-based electrolytes are typically used in high-efficiency DSSCs. However, Ru dyes are expensive and require a complex synthesis process. Organic solvents are toxic, environmentally hazardous, and explosive, and can cause leakage problems due to their low surface tension. This review summarizes and discusses previous works to replace them with natural dyes and water-based electrolytes to fabricate low-cost, safe, biocompatible, and environmentally friendly DSSCs. Although the performance of “eco-friendly DSSCs” remains less than 1%, continuous efforts to improve the PCE can accelerate the development of more practical devices, such as designing novel redox couples and photosensitizers, interfacial engineering of photoanodes and electrolytes, and biomimetic approaches inspired by natural systems.

A Dynamic Threshold Cancellation Technique for a High-Power Conversion Efficiency CMOS Rectifier

Power conversion efficiency (PCE) has been one of the key concerns for power management circuits (PMC) due to the low output power of the vibrational energy harvesters. This work reports a dynamic threshold cancellation technique for a high-power conversion efficiency CMOS rectifier. The proposed rectifier consists of two stages, one passive stage with a negative voltage converter, and another stage with an active diode controlled by a threshold cancellation circuit. The former stage conducts the signal full-wave rectification with a voltage drop of 1 mV, whereas the latter reduces the reverse leakage current, consequently enhancing the output power delivered to the ohmic load. As a result, the rectifier can achieve a voltage and power conversion efficiency of over 99% and 90%, respectively, for an input voltage of 0.45 V and for low ohmic loads. The proposed circuit is designed in a standard 130 nm CMOS process and works for an operating frequency range from 800 Hz to 51.2 kHz, which is promising for practical applications.

A High Power-Conversion-Efficiency Voltage Boost Converter with MPPT for Wireless Sensor Nodes

A high power-conversion-efficiency voltage boost converter with MPPT for wireless sensor nodes (WSNs) is proposed in this paper. Since tiny wireless sensor nodes are all over complex environments, an efficient power management system (PMS) must be equipped to achieve long-term self-power supply and maintain regular operation. It is common to use Photovoltaic cells (PV) to harvest sunlight in the environment. However, most existing interface boost integrated circuits for the PV cell have low efficiency. This paper presents a voltage boost converter (VBC) with high power conversion efficiency (PCE) for WSNs. The integrated circuit (IC) designed in this paper includes a novel four-phase high-efficiency charge pump module, an ultra-low-power perturbation observation (P&O) MPPT control circuit module, a feedback control module, a nano-ampere current reference, etc. Manufactured in a standard 0.35 um complementary metal-oxide-semiconductor (CMOS) technology, the chip area is 3.15 mm × 2.43 mm. Test results demonstrate that when the output voltage of the PV cell is more than 0.5 V, VBC can improve the voltage to 3Vin, and the calculated voltage conversion efficiency can reach 99.4%. P&O MPPT algorithm makes output power improving 8.53%. Furthermore, when the output load current is 297uA, the output PCE achieves 85.1%.

Characterizations of Galena as Potential Photosensitizer in a Natural Dye-Sensitized Solar Cell

Dye is one of the principal parts for high power conversion efficiency in a Dye-Sensitized Solar Cell. Conspicuous developments have taken place via the work of several researchers in the engineering of novel dye structures so as to enhance the performance of the system. The properties of a natural mineral dye were studied in this work. The structure of the dye was determined and discovered to have contains constituents that could enhance better absorption of solar radiation for use in a Dye-Sensitized Solar Cell (DSSC). The Lead sulphide and iron content of the mineral dye studied as revealed by the X-Ray diffraction analysis done suggest this. The X-Ray Fluorescence (XRF) done revealed that the concentration of Lead and Iron (Fe) is high as compared to other elements present in the material, probably as a result of the fact that it is a geological sample (of the earth) and which may even suggest its colour and hence makes it absorbs solar radiation of visible region at its wavelength (around 380 nm – 800 nm). The functional groups present in the dye as obtained from the Fourier transform infrared spectroscopy are the Amine, Carbonyl, and hydroxyl groups, all of which confirm the suitability of the dye material in photosensitizing a semiconductor in a DSSC. The absorption spectra of the dye within the visible region of electromagnetic radiation show that the material has high, increased, and stable absorption of visible light which is suggesting a more durable natural dye for a DSSC than the easily degraded natural dyes of plants source.

Silicon heterojunction-based tandem solar cells: past, status, and future prospects

Due to stable and high power conversion efficiency (PCE), it is expected that silicon heterojunction (SHJ) solar cells will dominate the photovoltaic market. So far, the highest PCE of the SHJ-interdigitated back contact (IBC) solar cells has reached 26.7%, approximately approaching the theoretical Shockley–Queisser (SQ) limitation of 29.4%. To break through this limit, multijunction devices consisting of two or three stacked subcells have been developed, which can fully utilize the sunlight by absorbing different parts of the solar spectrum. This article provides a comprehensive overview of current research on SHJ-based tandem solar cells (SHJ-TSCs), including perovskite/SHJ TSCs and III–V/SHJ TSCs. Firstly, we give a brief introduction to the structures of SHJ-TSCs, followed by a discussion of fabrication processes. Afterwards, we focus on various materials and processes that have been explored to optimize the electrical and optical performance. Finally, we highlight the opportunities and challenges of SHJ-TSCs, as well as personal perspectives on the future development directions in this field.

Methods of Stability Control of Perovskite Solar Cells for High Efficiency

The increasing demand for renewable energy devices over the past decade has motivated researchers to develop new and improve the existing fabrication techniques. One of the promising candidates for renewable energy technology is metal halide perovskite, owning to its high power conversion efficiency and low processing cost. This work analyzes the relationship between the structure of metal halide perovskites and their properties along with the effect of alloying and other factors on device stability, as well as causes and mechanisms of material degradation. The present work discusses the existing approaches for enhancing the stability of PSC devices through modifying functional layers. The advantages and disadvantages of different methods in boosting device efficiency and reducing fabrication cost are highlighted. In addition, the paper presents recommendations for the enhancement of interfaces in PSC structures.

A Review on Perovskite/Silicon Tandem Solar Cells

The tandem Solar cell has high power conversion efficiency (PCE), so they are taken as the next step in photovoltaic evolution. The tandem solar cell also overcome the limitations of Single-junction solar cells by reducing thermalization losses and also reduce the fabrication cost. The fabrication of tandem solar cells is highly efficient after the origination of halide perovskite absorber material, this material will shape the future of tandem solar cells. Researchers have already shown that this material can convert light more efficiently than standalone sub cell. Today, researchers around the world are keeping the configuration of a tandem solar cell as their agenda. A Tandem solar cell is a stacking of multiple layers having different bandgaps with specific maximum absorption and width. We reviewed perovskite/silicon tandem solar cells with different sub-module configurations. Move forward, we discuss the tandem module technology, sub cell of a tandem can be wired in several ways two terminals 2T monolithic and mechanically stacked, a four-terminal 4T mechanically stacked, and three-terminal 3T monolithic stack devices. This review paper provides a side-by-side comparison of theoretical efficiencies of multijunction solar cells. The highest efficiency has been evaluated at 39.4% for a three-level structure.

Mixed 2D-3D Halide Perovskite Solar Cells

The 3D-perovskite halides have gained a considerable reputation versus their counterpart semiconductor materials since they achieved a remarkable high-power conversion efficiency of 25.2% within a decade. Perovskite solar cells also have some problems as lattice degradation and sensitivity against moisture, oxygen, and strong irradiation. The perovskite instability is the drawback in front of this emerging technology towards mass production and commercialization. 2D-perovskites, with the general formula A2Bn − 1MnX3n + 1, have been recently introduced to overcome some of the drawbacks of the stability of 3D-perovskites; however, this is at the expense of sacrificing a part of the power conversion efficiency. Mixed 2D/3D perovskites could solve this dilemma towards the way to high stability-efficiency perovskites. The research is expected to obtain highly stable and efficient mixed 2D/3D perovskite solar cells in the few coming years. This chapter reviews 2D-perovskites’ achieved progress, highlighting their properties, current trends, challenges, and future prospects.