Search results for "photovoltaicS"
showing 10 items of 178 documents
Photocycle of Excitons in Nitrogen-Rich Carbon Nanodots: Implications for Photocatalysis and Photovoltaics
2020
Nitrogen-rich carbon nanodots have emerged as promising nanomaterials for a wide range of applications where a highly emissive and photoactive material with low toxicity and cost-effectiveness is required. One of their hallmarks is indeed a bright, tunable fluorescence of excitonic nature. Disentangling the origin of their optical absorption and fluorescence properties and uncovering relaxation channels and interactions with solvents are some of the most debated issues in the field. Uncovering these aspects is essential for targeted applications, especially in the fields of photocatalysis but also photovoltaics and optoelectronics. Here, we present dedicated transient absorption measurement…
Local Bonding Influence on the Band Edge and Band Gap Formation in Quaternary Chalcopyrites
2017
Quaternary chalcopyrites have shown to exhibit tunable band gaps with changing anion composition. Inspired by these observations, the underlying structural and electronic considerations are investigated using a combination of experimentally obtained structural data, molecular orbital considerations, and density functional theory. Within the solid solution Cu2ZnGeS4-x Se x , the anion bond alteration parameter changes, showing larger bond lengths for metal-selenium than for metal-sulfur bonds. The changing bonding interaction directly influences the valence and conduction band edges, which result from antibonding Cu-anion and Ge-anion interactions, respectively. The knowledge of the underlyi…
ZnS Ultrathin interfacial layers for optimizing carrier management in Sb2S3-based photovoltaics
2021
Antimony chalcogenides represent a family of materials of low toxicity and relative abundance, with a high potential for future sustainable solar energy conversion technology. However, solar cells based on antimony chalcogenides present open-circuit voltage losses that limit their efficiencies. These losses are attributed to several recombination mechanisms, with interfacial recombination being considered as one of the dominant processes. In this work, we exploit atomic layer deposition (ALD) to grow a series of ultrathin ZnS interfacial layers at the TiO2/Sb2S3 interface to mitigate interfacial recombination and to increase the carrier lifetime. ALD allows for very accurate control over th…
Role of TiO2 in Highly Efficient Solar Cells
2021
Titanium dioxide (TiO2) is a naturally occurring oxide of titanium. It has a wide range of applications. It has three metastable phases, which can be synthesized easily by chemical routes. Usage of TiO2 in thin-film solar cells has gained much attention in increasing the performance of the cell. The objectives are to harvest the freely available earth’s energy and to gain expertise in yielding a maximum conversion efficiency. Various strategies are employed to face the challenges in improving the efficiency of solar cells. This study provides a broad view of the usage of different forms of TiO2 layers, like nanochannel, porous, nanotubes, and mesoporous layers, in enhancing electron injecti…
Energy planning methodology of net-zero energy solar neighborhoods in the Mediterranean basin
2016
The article proposes a simplified methodology to optimize solar energy gains at district level in the Mediterranean area toward the achievement of the net-zero energy district target, to be applicable as well in similar hot climates. The approach includes a wide use of parametric analysis to explore the most impactful aspects of the design of solar net-zero energy districts: single unit shape, building mutual distances, road shape, building orientation, photovoltaics area availability to identify the optimal design solution. Thirty-two different district configurations are explored: results show that in the Mediterranean context, it is possible to reach the net-zero energy district target i…
Vapor phase epitaxy of Hg1−xCdxI2 layers on CdTe substrates
1997
Vapor phase epitaxy (VPE) has been studied to grow Hg1 − xCdxI2 epitaxial layers on CdTe bulk substrates. The effect of the VPE growth conditions on the morphology, composition and crystalline quality of Hg1 − xCdxI2CdTe heterostructures has been investigated. It has been shown that 10–30 μm thick Hg1 − xCdxI2 layers can be successfully grown using an α-HgI2 polycrystalline source under isothermal conditions at a temperature in the range 170–240°C for the time period 20–50 h. Interestingly, the VPE growth was found to consist of two successiv stages with different kinetics as follows: (1) a fast growth of an HgI2 platelet layer on the CdTe substrate surface and (2) a slow growth of an Hg1 −…
Perovskite solar cells join the major league
2015
Just six years after their discovery, organolead halide perovskite solar cells have taken the lead among emergent photovoltaic (PV) technologies, thanks to the demonstration of power conversion efficiencies (PCEs) of up to 20% ( 1 , 2 ). The perovskite precursor compounds are abundant and inexpensive and can easily be converted into thin films. Perovskite photovoltaics can therefore, in principle, generate electricity at a very low cost. However, high efficiencies have been limited to very small devices. On page 944 of this issue, Chen et al. ( 3 ) report perovskite solar cells of 1 cm2 with a certified efficiency of 15%.
A new CdTe/ZnO columnar composite film for Eta-solar cells
2002
Abstract First results of CdTe deposition on ZnO films consisting of free standing single crystalline columns of several micrometers height and ∼100– 200 nm diameter are presented. The ZnO films have been obtained by electrochemical deposition on conductive glass. Morphology, structural and optical properties of the nanostructured columnar CdTe/ZnO composite films have been studied. The cadmium telluride ( 40 nm thick) deposited by vapor-phase epitaxy under dynamical vacuum is lining the ZnO columns as a continuous smooth thin film with conformal coverage. The polycrystalline CdTe layer is a mixture of cubic and hexagonal phases and is semiconductor with a direct band gap optical transition…
Ligand removal from soluble CdTe nanocrystals evidenced by time-resolved photoluminescence spectroscopy
2008
We present experimental studies on the effect of pyridine treatment on the optical properties of ligand-stabilized colloidal CdTe nanocrystals. We demonstrate, by quasi-stationary and time-resolved photoluminescence (PL) spectroscopy, a drastic reduction in the PL lifetime and a concomitant decrease in the PL yield by more than 90% when dissolving the nanocrystals in pyridine. The pyridine solvent efficiently removes the ligand shell and thus enables a rapid energy transfer from the quantum dot to optically dark surface states or into the solvent. The demonstrated removal of the ligand shell is a key step towards integrating such CdTe nanocrystals in hybrid organic/inorganic nanocomposites,…
Real time digital pulse processing for X-ray and gamma ray semiconductor detectors
2013
Abstract Digital pulse processing (DPP) systems, based on direct digitizing and processing of detector signals, have recently been favoured over analog electronics, ensuring higher flexibility, stability, lower dead time and better spectroscopic performance. In this work, we present the performance of a new real time DPP system for X-ray and gamma ray semiconductor detectors. The system is based on a commercial digitizer equipped with a custom DPP firmware, developed by our group, for on-line pulse height and shape analysis. X-ray and gamma ray spectra measurements with cadmium telluride (CdTe) and germanium (Ge) detectors highlight the excellent performance of the system both at low and hi…