Synthesis of Si and CdTe quantum dots and their combined use as down-shifting photoluminescent centers in Si solar cells (original) (raw)
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Electronics
Silicon quantum dots (Si-QDs) with luminescent downshifting properties have been used for the efficiency enhancement of solar cells. In this study, Phenylacetylene-capped silicon quantum dots (PA Si-QDs) have been fabricated and applied as luminescent downshifting material on polycrystalline silicon solar cells, by dropcasting. The PA Si-QD coated solar cell samples presented an average increase in the short circuit current (Isc) of 0.75% and 1.06% for depositions of 0.15 mg and 0.01 mg on 39 mm × 39 mm pc-Si solar cells, respectively. The increase was further enhanced by full encapsulation of the sample leading to overall improved performance of about 3.4% in terms of Isc and 4.1% in terms of power output (Pm) when compared to the performance of fully encapsulated reference samples. The PA Si-QD coating achieved a reduction in specular reflectance at 377 nm of 61.8%, and in diffuse reflectance of 44.4%. The increase observed in the Isc and Pm is a promising indicator for the use of...
Materials for Renewable and Sustainable Energy, 2016
We report the synthesis and characterization of Carbon and CdTe quantum dots (QDs), as well as the observed improvement in the power conversion efficiency (PCE) of photovoltaic devices upon the incorporation of the synthesized aforementioned nanostructures. Even though C quantum dots were observed to have a relatively smaller influence on solar cell performance, they are considered to be a more attractive option due to their affordability and minimal impact in the environment that could ultimately promote their widespread utilization on photovoltaic structures.
The Journal of Physical Chemistry C, 2014
A simple optical model is presented to describe the influence of a planar luminescent down-shifting layer (LDSL) on the external quantum efficiencies of photovoltaic solar cells. By employing various visible light-emitting LDSLs based on CdTe quantum dots or CdSe/CdS core−shell quantum dots and tetrapods, we show enhancement in the quantum efficiencies of thin-film CdTe/CdS solar cells predominantly in the ultraviolet regime, the extent of which depends on the photoluminescence quantum yield (PLQY) of the quantum dots. Similarly, a broad enhancement in the quantum efficiencies of crystalline Si solar cells, from ultraviolet to visible regime, can be expected for an infrared emitting LDSL based on PbS quantum dots. A PLQY of 80% or higher is generally required to achieve a maximum possible short-circuit current increase of 16 and 50% for the CdTe/CdS and crystalline Si solar cells, respectively. As also demonstrated in this work, the model can be conveniently extended to incorporate LDSLs based on organic dyes or upconverting materials. Article pubs.acs.org/JPCC
Journal of Physics: Conference Series, 2016
We report the synthesis and characterization of silicon quantum dots that exhibit down-shifting, photo luminescent characteristics. We also discuss the fabrication and characterization of single crystal Silicon (c-Si) Solar cells with and without the influence of the previously mentioned QDs. The incorporation of these nanostructures triggers improvements in the performance of the fabricated photovoltaic devices, especially in the open circuit voltage (V oc) and short circuit current density (J sc). Specifically, the experimental results showed increments in the V oc from 532.6 to 536.2 mV and in the J sc from 33.4 to 38.3 mA/cm 2. The combined effect of those improved V oc and J sc values led to an increment in the power conversion efficiency (PCE) from 11.90 to 13.37%. This increment represents an improvement of the order of 12.4% on the power conversion efficiency of this type of solar cells. The observed results could be conducive to promoting the proliferation of photovoltaic structures.
Silicon nanocrystals (Si NCs) embedded in Si-based dielectrics provide a Si-based high band gap material (1.7 eV) and enable the construction of all-crystalline Si tandem solar cells. However, Si nanocrystal formation involves high-temperature annealing which deteriorates the properties of any previously established selective contacts. The inter-diffusion of dopants during high-temperature annealing alters Si NC formation and limits the built-in voltage. Furthermore, most devices presented so far also involve electrically active bulk Si and therefore do not allow a clear separation of the observed photovoltaic effect of the quantum dot layer from that of the bulk Si substrate. A membrane route is presented for quantum dot based p-i-n solar cells to overcome these limitations. In this approach, the formation of both selective contacts is carried out after high-temperature annealing and therefore not affected by the latter. P-i-n solar cells are investigated with Si NCs embedded in silicon carbide in the intrinsic region. Open-circuit voltages of up to 370 mV are shown for the NC layer. An optical model of the device is presented for improving the cell current. Finally device failure due to damaged insulation layers is analysed by electron beam induced current measurements.
Renewable Energy, 2019
Nano-scale engineering for optoelectronic properties of silicon has shown its suitability in the modern era of Photovoltaic. The major focus is on Silicon quantum dots (Si QDs) which behave like an atom restricting the free movement of electrons. It provides an opportunity to control the energy states by manipulating the size of the Si QDs. Such closely packed Si QDs together form quasi-crystalline structures that lead to the formation of superlattices in different Si energy bands. Significant efforts have been devoted to the control of size and distribution density of the Si QDs. A current status of research efforts on the factors that influence the size and distribution density of Si QDs within the silicon-based matrix are discussed here. A brief summary of various fabrication techniques and mechanisms behind the growth of Si QDs are discussed in this study. A comparison on the effect of growth parameters for Si QDs with various dielectric/semiconductor matrix such as Silicon dioxide, Silicon nitride, Silicon carbide and the combination of the tandem solar cell is highlighted based on recent research progress. An overview towards the state of the art in the development, challenges and future trends of Si QDs to dictate as the third generation photovoltaic material are discussed in detail.
Si quantum dots for solar cell fabrication
Materials Science and Engineering B-advanced Functional Solid-state Materials, 2009
Thin film stacks, made of Si-rich SiO alternated with SiO 2 layers, have been deposited by reactive RF sputtering starting from Si and SiO 2 targets, respectively. Crystalline quantum dots (QDs) have been nucleated by Si precipitation from the Si-rich SiO phase using high temperature annealing. PL measurements evidenced a blueshift of the emission peak which has been attributed to a reduction of the Si QD size. Electrical resistivity measurements showed a semiconducting-like behaviour. QD size affect the resistivity values and the activation energies. We have tentatively interpreted the electrical behaviour of this quantum structure by using a Meyer-Neldel Rule conventionally used to explain the electrical properties of nanoporous silicon.
Enhanced efficiency for c-Si solar cell with nanopillar array via quantum dots layers
Optics Express, 2011
The enhanced efficiency of the crystalline silicon (c-Si) solar cell with nanopillar arrays (NPAs) was demonstrated by deployment of CdS quantum dots (QDs). The NPAs was fabricated by the colloidal lithography and reactive-ion etching techniques. Under a simulated one-sun condition, the device with CdS QDs shows a 33% improvement of power conversion efficiency, compared with the one without QDs. For further investigation, the excitation spectrum of photoluminescence (PL), absorbance spectrum, current-voltage (I-V) characteristics, reflectance and external quantum efficiency of the device was measured and analyzed. It is noteworthy that the enhancement of efficiency could be attributed to the photon downconversion, the antireflection, and the improved electrical property.
Solar Energy Materials and Solar Cells, 2010
In this work, Si quantum dots in SiO 2 /Si 3 N 4 hybrid matrix on quartz substrates were synthesized by magnetron sputtering of alternating silicon rich oxide and Si 3 N 4 layers followed by different postdeposition anneals. XRD results indicate that the average dimension of the Si nanocrystals varies from 1.6 to 5.2 nm. The size and crystallization of the Si nanocrystals are dependent on a number of factors, including the annealing method, the SRO thickness and the Si 3 N 4 barrier thickness, as evidenced in XRD and Raman measurements. In particular, thicker Si 3 N 4 barrier layers seem to be able to suppress the growth of Si nanocrystals more effectively. PL measurements suggest the apparent bandgap of the samples investigated in this work is in the range 1.12-1.67 eV, which demonstrates the effect of quantum confinement. More interestingly, analysis of the PL data using the modified EMA equations clearly suggests that the PL peak energy not only depends on the size of the nanocrystals but also gets affected by other details in nanocrystal growth. A tentative core-shell model is constructed to illustrate our explanation. These findings offer a preliminary understanding of the nanocrystal growth and radiative recombination processes in this newly synthesized material for photovoltaic applications.
Silicon quantum dot absorber layers are used as building blocks for all-silicon tandem solar cells. A control of the Si nanocrystal size allows the adjustment of essential material parameters such as bandgap and oscillator strengths due to size quantization effects. This allows to fabricate silicon based top and middle cells with an engineered and optimized band gap for all-silicon tandem cells, increasing the theoretical efficiency limit of a silicon solar cell from 29 % to 42.5 % for two and 47.5 % for three cells . In this paper, we present the optical and electrical characterization of Si quantum dots embedded in a dielectric SiC matrix for solar cell applications with special emphasis on the electrical transport through the superstructure and the reduction of recombination via defects at the interface between nanocrystals and the dielectric matrix. In order to build a photovoltaic device, both carrier transport properties and recombination properties have to be optimised by appropriate deposition, annealing and passivation procedures.