Fengning Yang

Abstract:

The efficiency and longevity of metal-halide perovskite solar cells are typically dictated by nonradiative defect-mediated charge recombination. In this work, we demonstrate a vapor-based amino-silane passivation that reduces photovoltage deficits to around 100 millivolts (>90% of the thermodynamic limit) in perovskite solar cells of bandgaps between 1.6 and 1.8 electron volts, which is crucial for tandem applications. A primary-, secondary-, or tertiary-amino–silane alone negatively or barely affected perovskite crystallinity and charge transport, but amino-silanes that incorporate primary and secondary amines yield up to a 60-fold increase in photoluminescence quantum yield and preserve long-range conduction. Amino-silane–treated devices retained 95% power conversion efficiency for more than 1500 hours under full-spectrum sunlight at 85°C and open-circuit conditions in ambient air with a relative humidity of 50 to 60%.

Abstract:

This paper discusses sustainable renewable energy policies. The method used in this paper is a descriptive method that collects data from various sources literature studies and previous research. The results of the literature review show that the development of renewable energy in the European Union has three clusters dividing the share of renewable energy and the degree of dependency on energy imports based on the country. In Pakistan, the government has been designing a renewable energy policy since 2006 to supply sustainable energy to all consumers. In Nigeria, the electricity crisis and the need to reduce greenhouse gases spurred the development of renewable energy. Denmark has moved to wind power sources by increasing the share of renewable energy in the domestic electricity supply. The government encourages local ownership in the renewable energy sector, and many neighborhoods are connected to district heating systems that use renewable energy such as biomass. Increased investment in renewable energy technology will aid in addressing global energy concerns and hastening the transition to a low-carbon economy.Tulisan ini membahas tentang kebijakan energi terbarukan berkelanjutan. Metode yang digunakan dalam tulisan ini adalah metode deskriptif yang mengumpulkan data dari berbagai sumber dan studi literatur serta penelitian terdahulu. Hasil dari tinjauan literatur menunjukkan bahwa perkembangan energi terbarukan di Uni Eropa memiliki tiga kluster yang membagi negara-negara berdasarkan pangsa energi terbarukan dan tingkat ketergantungan impor energi. Di Pakistan, pemerintah telah merancang kebijakan energi terbarukan sejak tahun 2006 untuk memasok energi berkelanjutan kepada semua konsumen. Di Nigeria, krisis listrik dan kebutuhan untuk mengurangi gas rumah kaca memacu pengembangan energi terbarukan. Meskipun Nigeria memiliki potensi energi terbarukan yang besar, perkembangannya masih lambat. Diperlukan upaya lebih lanjut untuk meningkatkan pemanfaatan energi terbarukan melalui perjanjian kemitraan swasta, investasi dalam penelitian dan pengembangan, dan kebijakan berorientasi pasar.  Denmark telah melakukan peralihan ke sumber energi terbarukan dengan meningkatkan pangsa energi terbarukan dalam pasokan listrik domestik. Tenaga angin menjadi salah satu komponen utama energi terbarukan di Denmark. Pemerintah mendukung kepemilikan lokal dalam sektor energi terbarukan, dan sejumlah besar rumah tangga terhubung ke pemanas distrik yang menggunakan energi terbarukan seperti biomassa. Investasi yang lebih besar dalam teknologi energi terbarukan akan membantu mengatasi tantangan energi global dan mempercepat transisi ke ekonomi rendah karbon yang berkelanjutan

Abstract:

Constructing stable electrodes which function over long timescales at large current density is essential for the industrial realization and implementation of water electrolysis. However, rapid gas bubble detachment at large current density usually results in peeling-off of electrocatalysts and performance degradation, especially for long term operations. Here we construct a mechanically-stable, all-metal, and highly active CuMo₆S₈/Cu electrode by in-situ reaction between MoS₂ and Cu. The Chevrel phase electrode exhibits strong binding at the electrocatalyst-support interface with weak adhesion at electrocatalyst-bubble interface, in addition to fast hydrogen evolution and charge transfer kinetics. These features facilitate the achievement of large current density of 2500 mA cm^-2 at a small overpotential of 334 mV which operate stably at 2500 mA cm^-2 for over 100 h. In-situ total internal reflection imaging at micrometer level and mechanical tests disclose the relationships of two interfacial forces and performance of electrocatalysts. This dual interfacial engineering strategy can be extended to construct stable and high-performance electrodes for other gas-involving reactions.

Abstract:

Direct bandgap perovskite and indirect bandgap Si, which form the two active layers in a tandem solar cell configuration, have different optoelectronic properties and thicknesses. The charge-carrier dynamics of the two-terminal perovskite-on-Si tandem solar cell in response to a supercontinuum light pulse is studied using transient photocurrent (TPC) measurements. Spectral dependence of TPC lifetime is observed and can be classified into two distinct timescales based on their respective carrier generation regions. The faster timescale (∼500 ns) corresponding to the spectral window (300-750 nm) represents the top-perovskite sub-cell, while the slower timescale regime of ∼25 μs corresponds to the bottom-Si sub-cell (>700 nm). Additionally, under light-bias conditions, the transient carrier dynamics of the perovskite sub-cell is observed to be coupled with that of the Si sub-cell. A sharp crossover from the fast-response to a slow-response of the device as a function of the light-bias intensity is observed. These results along with a model based on transfer matrix formulation highlight the role of charge-carrier dynamics in accessing higher efficiencies in tandem solar cells. The carrier transit times and lifetimes in addition to their optical properties need to be taken into account for optimizing the performance.

Abstract:

The use of highly-active and robust catalysts is crucial for producing green hydrogen by water electrolysis as we strive to achieve global carbon neutrality. Noble metals like platinum are currently used catalysts in industry for the hydrogen evolution, but suffer from scarcity, high price and unsatisfied performance and stability at large current density, restrict their large-scale implementations. Here we report the synthesis of a type of monolith catalyst consisting of a metal disulfide (e.g., tantalum sulfides) vertically bonded to a conductive substrate of the same metal tantalum by strong covalent bonds. These features give the monolith catalyst a mechanically-robust and electrically near-zero-resistance interface, leading to an excellent hydrogen evolution performance including rapid charge transfer and excellent durability, together with a low overpotential of 398 mV to achieve a current density of 2,000 mA cm^-2 as required by industry. The monolith catalyst has a negligible performance decay after 200 h operation at large current densities. In light of its robust and metallic interface and the various choices of metals giving the same structure, such monolith materials would have broad uses besides catalysis.