Hello ,
I want you to write my report using some of the information in the literature , and use this experiment reference to write the report write about the
same experiment on the literature on this link https://www.frontiersin.org/articles/10.3389/fenrg.2019.00011/full
+ use other sources if needed
+ the title need to be changed
Main Components of Academic Report:
1.
Report Title:
It must be clear and concise. In the title page (page 1), mention the names of
report author and the date of academic studys preparation.
2.Abstract:
Although the Abstract is always written at the beginning of page 2, it must be written at the end of
entire report, which should include a summary of reports main points.
3.
Reports Table of Contents: It
is required to mention the main headings, then the sub-headings, along with the
page numbers besides every heading. Then, drafting a list of all figures,
drawings and tables stated in the report.
4.
Writing an Introduction:
If the report is practical, the problem
need to be addressed must be firstly introduced or clarifying its importance in
addition to the surrounding circumstances and the respective organization.
While, in main reports, the introduction provides an overview of the relevant
subject.
5.
Write the tenor of study or subject to be detailed.
6.
Conclusion:
Includes the new ideas and propositions or recommendations that have been
reached.
7.References: A
list of all sources that are used in the preparation of the report.
The efficiency of Zinc Oxide Quantum Dots in Solar Cell and its Unique Properties
Introduction
Solar technology is not new to humans. Historical data shows that the concentration of the sun’s heat to light fires and burn down ant hills has been used since the 7th century BC. Today, solar energy is used extensively to manufacture and produce industrial products. We even have solar-powered vehicles, planes and buildings. However, the credit goes to scientists who have tirelessly pursued this concept since the discovery of the photovoltaic effect by Alexandre Becquerel in 1839 (Kamak 2019). He noticed that particular materials produce light when exposed to sunlight. The scientific community’s attention was brought towards solar power technology after Albert Einstein published his Nobel Prize-winning research on the photoelectric effect. Since then, the efficiency of solar energy has increased exponentially. At the same time, the cost of production of solar cells has decreased. The first mega applications of solar cells were in Soyuz 1 and Skylab space station, which orbited the earth in the 1970s (Kamak 2019). To further increase the efficiency of solar cells, scientists have incorporated various elements, including zinc oxide nanoparticles. Using past peer-reviewed research done by accomplished scientists globally- literature review, this paper highlights the efficiency of zinc oxide in quantum dots in solar cells and its unique properties.
Findings on Quantum Dots-Sensitized Solar Cells
Quantum dots are a exceptional kind of semiconductors containing periodic groups of II-VI, III-IV, or IV-VI materials that can confine electrons (Jasim 2014). Depending on the size of the radius, quantum dots are categorized as non-natural molecules with energy gaps and levels. The energy band is inversely proportional to the size of the quantum dot. Due to these properties of the adjustable bandgap, they are used to make solar cells. Compared to crystalline silicon solar cells, quantum dots cells have high power efficiency because they discharge up to three electrons per photon during exciton generation. Theoretically, this boosts power output from 20% to 65% (Jasim 2014). The factors that characterize the performance of solar cells are open-circuit voltage, short circuit current and the fill factor. However, the fill factor is a function of the other two. According to Tian et al. (2013), semiconductor quantum dots have attained great consideration due to their multipurpose optical and electrical aspects. Moreover, quantum solar cells are high performing and cost-efficient. According to Emin et al. (2011), quantum dots solar cells will replace the existing photovoltaic devices. These statements are further reinforced by Calderone (2018), who argues that by 2030 solar power technology will have grown by a factor of 10. The advantages they have over standard silicon PV panels are performance reduction of elements such as silicon, copper indium and gallium selenide. Furthermore, quantum dots solar cell has band gaps that can be adjusted depending on the energy levels by altering the size of dots.
Findings on Application and Efficiency of Zinc Oxide in Quantum Dots-Sensitized Solar Cells
After years of study, Zinc Oxide has emerged as one of the chief significant elements in quantum dot solar cells compared to other metal oxides. This has been enhanced by the increased application of solar energy and the drive to use renewable energy sources fuelled by climate change initiatives. In that regard, governments, institutions and non-governmental organizations have financed research and projects focused on enhancing solar energy. Nonetheless, advancement in technology and its influence on solar power cannot be ignored. According to Zhu (2015), ZnO is applied as a down-shifting layer deposited in the forward-facing side of the solar cell. It effectively helps in converting UV- blue photons into more efficient visible photons used by photovoltaic solar cells. Scientifically, the UV photons are less efficient in solar cells and thus need to boost their productivity.
Furthermore, Wei et al. (2020) research concluded that the addition of Zinc Oxide as an Electron Transport Layer (ETL) improved the proficiency of lead sulphide quantum dot solar cells. Statistically, the power produced increased by approximately 2%. This means conversion of photons was boosted and thus higher current density. However, Wei et al. (2020) add that solar cell productivity is pushed to higher levels by adding sodium chloride in the ETL. Moreover, Patidar et al. (2013) argue that mono-spread zinc oxide has gained momentum in its application in solar cells because of its wide bandgap (3.37 Ev). Also, Peng & Qin (2011) agrees with other researchers that ZnO is the best candidate amongst the metal oxides used as photoelectrodes in solar cells. However, ZnO is supplemented with TiO2, which has a large surface area for harvesting sunlight, to further boost its efficiency. Moreover, a study done by Singh et al. (2012) found that the efficiency of cadmium sulphide quantum dots increased by 1.3% when it was synthesized with ZnO nanoparticles. Wibowo et al. (2020) sheds more light on the application of ZnO in solar cells by postulating that various structures of ZnO materials are used. He adds that ZnO can be grown directly on the substrate because of its electron pathways. Due to this property, ZnO nanostructured materials are applied in heterojunction architectures. It is also combined with perovskite materials to increase operational stability. This makes it more applicable to solar cells compared to other metal oxides.
Another research done by Ren et al. (2021) concluded that when ZnO nanocrystals are deposited in PbS quantum dot solar cells having Indium Tin Oxides reduced carrier recombination between oxides and PbS interface decreases. Furthermore, an experiment done by Ren et al. (2020) using Mg-doped ZnO on the output of PbS quantum dot solar cells was established to be less efficient without the ZnO nanoparticles layer. However, on the application of the ZnO thin layer, the solar cell performance improved from 5.52% to 7.06%. This was due to diminished interface recombination. Ren et al. (2021) articulate that the output of quantum dot solar cells will increase dramatically in the coming years. Similarly, the quantum dot solar cells used in the energy sector will explode compared to conventional photovoltaic technology. This will be ascribed to the development of ligand exchange techniques, interface engineering and optimal device architecture. According to Sahu et al. (2020), quantum dot sensitized solar cells are third-generation solar cells. This is due to their efficiency, compact sizes, composition tenability and ability to absorb a broad solar spectrum compared to other generations of solar cells. When dye-sensitized cells and quantum dot sensitized solar cells are compared, both have power conversion efficiency (PCE) of about 12%.
Research on Unique Properties of Zinc Oxide
In recent years, semiconducting nano-crystalline materials have been studied massively because of their potential technological applications ranging from biomedicine to quantum computing. Amongst the elements with versatile applications is zinc oxide. ZnO is a white inorganic compound that is almost insoluble in H2O. On crystallizing, it forms two compounds: hexagonal wurtzite and cubic zinc blende. However, wurtzite is more popular because of its stability (Tyona 2011). ZnO materials fall under group II-VI of binary compound semiconductors. According to Patidar et al. (2013), this is mainly due to its luminescent properties, low costs and wide-bandgap. Moreover, it is applied in solar cells because of its abundant availability, cheapness, nontoxicity, high electron mobility, low crystallization temperature, wide excitation binding energy of 60 meV and easiness in synthesizing. In other words, it combines the properties of organic and inorganic semiconductors. Some of the pros of organic semiconductors are flexibility and synthesis, while inorganic semiconductors are more stable and have high electron mobility (Patidar et al. 2013). The large excitation binding energy allows the ZnO to be stable at room temperature.
Moreover, Wibowo et al. (2020) add that zinc oxide has gained potential in its usage in solar cells because of its extraordinary conductivity and stability against photo corrosion. He further articulates that solar cell inefficiency is attributed to low energy band gaps and losses that occur during electron transmission. To avoid this, engineers must consider the intrinsic stabilities of elements used in solar cells.
Hexagonal Wurtzite crystal structure of ZnO
Furthermore, aspects like high absorption efficiency of solar spectra, carrier kinesis, high conductivity and effective extraction of the agitated carriers (Wibowo et al. 2020). Another aspect that allows extensive application of ZnO in solar cells is its ability to absorb light in the UV region. Furthermore, the ability of zinc oxide nanoparticles to intensify absorption of spectrum in the visible region is increased by its combination with small energy gap elements like dye sensitizer, organic polymer and small bandgap semiconductors. Moreover, bulk zinc oxide has an excitation Bohr radius of 2.34nm (Wibowo et al. 2020). This increases its confinement effects which are significant during the synthesis phase. In addition, zinc oxide is regarded as one of the best polymorphs (Anta et al. 2012). This means it can be modelled into different structures depending on the synthesis method. Its surface control is also the best compared to other metal oxides. It can be synthesized into nanospheres, nanowires, nanorods, nanaflower, nanotubes, nanocrystals and 3D nanostructures. This further increases its application in various fields.
Furthermore, zinc oxide can be prepared using various methods, including either green synthesis or sputtering techniques. Electrodeposition, sol-gel, and successive ionic layer adsorption and reaction (SILAR) approaches are the most used to grow epitaxial films of zinc oxide and its alloys (Tyona 2011). The technique being applied depends on the application, costs and effectiveness. ZnO is doped with either Cu or Al to increase its performance in solar cells. However, Cu is the most used because of its high conductivity. This creates localized states within the zinc oxide bandgap and thus enhancing the green luminescence band. In addition, copper has high ionization energy, and it can thus substitute Zn in ZnO lattice.
According to Flickyngerov ´a et al. (2010), zinc oxide exhibits unique optoelectronic, pyroelectric, chemo electric and acoustoelectric properties, which make it applicable in many engineering sectors. In addition, Flickyngerov ´a et al. (2010) adds that zinc oxide can be implemented easily in microelectronic technology, including solar cells. Furthermore, its surface texture enhances light scattering and absorption in the solar cellalso, its great chemical steadiness and bond to silicon increase solar cell efficiency. Tyona (2018) adds that the effectiveness of zinc oxide nanostructures is improved by their optical and surface wettability properties.
Experiment on Quantum Dot Solar Cell
Due to the promising nature of quantum dot solar cells, researchers have made efforts to improve their efficiency. An experiment conducted by Ozu et al. (2019) demonstrated that the performance of ZnO nanowire-based colloidal quantum dot solar cells (CQDCS) was improved through SnO2 surface passivation. The team synthesized PbS CQDCS by mixing 6 mmol PbO, 15 mmol oleic acid (OA), and 50 ml 1-ocatadecene (ODE) to conduct the experiment. The materials are stirred energetically and vacuum degassed at ambient temperature for approximately 30 minutes and at 100 degrees Celsius for two hours (Ozu et al. 2019). At last, a clear lead oleate solution is attained. Other materials used were hexamethyldisilazane (TMS), CdCl2, toluene solution, nitrogen gas and octane. To measure the thickness and length of the materials: ZnO nanowire and SnO2, field-emission scanning electron microscope (FESEM) and high-resolution electronic microscope were used. After the SnO2 passivation, the PCE of ZnO was increased by 39% (Ozu et al. 2019). Overall, the output of the quantum dot solar cell increased from 5.6% to 7.8%. This shows that SnO2 passivation was effective in reducing charge recombination between the materials interfaces. The experiment demonstrated that the passivation layer is an efficient way of enhancing the efficiency of quantum dot solar cells.
Conclusion
In conclusion, it is evident that scientific efforts are being made towards green energy production and consumption. This has prompted extensive research on solar cells leading to quantum dots solar cells. The latter is advantageous because they can be regulated by adjusting the energy levels by altering the size of quantum dots. After years of research, zinc oxide has emerged as one of the most significant quantum dot solar cells materials. The use of ZnO is reinforced by its properties such as wide bandgap, large excitation binding energy (60 meV), and low crystallization temperature, nontoxicity and high electron mobility. By the application of zinc oxide in quantum dot solar cells, the overall performance of the cell is increased An experiment was conducted to demonstrate the effect of SnO2 surface passivation on the overall performance of ZnO nanowire-based colloidal quantum dot solar cells. The thickness of the materials used for the experiment was measured using a field-emission scanning electron microscope (FESEM). It was proved that the cell’s overall output improved from 5.65 to 7.8%. Furthermore, Surface passivation increased the PCE of ZnO by 39%. This was due to a decrease in charge recombination between material interfaces in the quantum dot solar cell. This proves that there is potential in green energy initiatives. By 2030, the popularity of quantum solar cells will have increased by a factor of 10.
References
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