Why perovskite/silicon tandem solar cells are the rising stars of renewable energy technologies nowadays?
The outstanding tool for developing perovskite/silicon tandem solar cell
- The importance of renewable energy
- Advantages and development potential of perovskite/silicon tandem solar cells
- The most powerful tool to support the development of perovskite/silicon tandem solar cell technolog
1. Renewable Energy
As the global population continues to increase and the public’s reliance on technological goods continues to increase, human demand for energy continues to increase. According to the estimates of the World Energy Council (https://www.worldenergy.org/), the human demand for electricity will double in 2060. If it is supplied by fossil fuel (Fossil Fuel), we In addition to facing the problem of depletion of fuel reserves, the greenhouse effect caused by the pollution of the environment caused by burning fossil fuels will also cause an unbearable catastrophe for human existence.
Therefore, the use of renewable energy (Renewable Energy) has become the only solution. There are many types of renewable energy, including: biomass fuel, geothermal, tidal energy, hydroelectric power, wind energy, hydrogen fuel and solar energy…etc. After considering the adequacy of energy supply, stability and conversion efficiency and other important factors, solar energy stands out and becomes one of the most reliant renewable energy projects in the world.
The application of solar energy is quite extensive, and there are three main modes :
(1) “Photoelectric conversion”: use solar cells to generate electricity.
(2) “Photocatalysis”: using catalysts for photocatalytic hydrogen production, carbon dioxide reduction, organic pollutant degradation, biomass energy conversion, etc.
(3) “Solar thermal energy”: use the thermal energy of sunlight to prepare hot water, store heat in salts, and perform seawater desalination, etc.
Solar energy is quite abundant. Earth receives 174 petawatts (PW) of incoming solar radiation (insolation) in the upper atmosphere. About 30 percent of solar energy is reflected back into space, while the rest is absorbed by clouds, oceans, and land. The solar spectrum at the Earth’s surface is mostly distributed in a small fraction of the near-ultraviolet, full visible, and near-infrared spectral ranges. The average solar energy received by the earth is about 1.7 × 1017 watts, and 1% of its energy is equivalent to supplying 7.4 billion people in the world for 200 days. Therefore, solar energy can be regarded as an infinite resource. ( Reference: Wikipedia: https://zh.m.wikipedia.org/zh-tw; World Materials Net https://www.materialsnet.com.tw/DocView.aspx?id=32994 )
2. The advantages and potentials of Perovskite-Silicon Tandem Solar Cells
For a long time, the material of solar cells has been dominated by the most commonly used semiconductor material – silicon crystal. However, since 2009, a special organometallic halide material “perovskite” has attracted the attention of scientists. “Perovskite” originally refers to calcium and titanium oxide CaTiO3 (structure can be expressed as ABX3), because the structure of organometallic halide is the same as perovskite ABX3, so it is collectively called perovskite. The perovskite used in solar cells has a high efficiency in absorbing light. After absorbing photons, it can be quickly separated into electrons and holes, which are sent to the electrodes to generate current. Such high efficiency makes scientists think, why not use perovskites to make solar cells? ( Reference: Pansci https://pansci.asia/archives/323726)
What are the advantages of making solar cells with perovskites?
(1) Simplified production process : When silicon crystal is used as the material, in order to reduce the number of defects in the crystal lattice, it must be treated at a high temperature of about 900 ° C for a long time, and then the diode solar cell is made by a semiconductor high vacuum and high temperature process. , the process is complicated and rigorous. However, perovskite solar cells are made in the form of solution-coated films, so they do not require such high temperatures and do not require a vacuum environment, and can be fabricated in a general environment.
(2) High energy conversion efficiency : The theoretical conversion efficiency of perovskite solar cells is > 40%. At present, the perovskite individual components that have been produced in the laboratory have reached a conversion efficiency of 25%. The battery is as high as 30%. ( Reference: Taiwan Perovskite Technology : https://www.tw-perovskite.com/3rdgenerationsolarcells )
However, perovskite solar cells are not perfect either. The biggest drawback is that the battery life is far less than that of silicon solar cells. In general, silicon solar cells have a lifespan of up to 30 years, but perovskite solar cells have a lifespan of only about 10 years.
In order to improve the successful conversion rate of solar cells for a wide range of internal efficiency and use of solar cells. In addition to improving battery life through appropriate material doping, innovative battery structures can also improve the structure of solar cells. The overall photoelectric conversion efficiency of the cell is high, among which the calcium ore/silicon tandem solar cell is the most representative product.
The team led by Professor Lin Weifang of National Taiwan University is the leader in the research of stacked crystalline ore/silicon layer solar cells, and the leader formed. This is also the crystalline layer when the layered solar cells are exposed to sunlight, and the materials are mined just right to form a crystal clear photocrystalline layer; the solar photocrystalline layer below the sun is a layered battery, which is the best choice for silicon solar cells. Excellent crystal. (please see Fig.1)
Fig. 1 The stacking of perovskite solar cells and silicon solar cells can increase the photoelectric conversion efficiency. ( Reference: Pansci https://pansci.asia/archives/323726 )
Another advantage of Prof. Lin’s stack design is that: due to the current life of perovskite solar cells is still far less than that of silicon solar cells, if the upper perovskite cell is damaged in the future, we can tear off the upper layer, re-sticking new perovskite solar cells, giving new life to the battery module.
3. The most helpful tool for the development of Perovskite-Silicon Tandem Solar Cells
Research reports published in many top journals show that Voc-loss open-circuit voltage loss analysis (hereinafter referred to as Voc-loss) is the most widely used by researchers today to continuously break through the efficiency limit of perovskite solar cells (PSCs). the most effective way.
Fig2. In recent years, the efficiency improvement of perovskite solar cells has been studied, and the statistical graph of the number of published papers has been analyzed by Voc loss.
Figure 2 shows the statistics of published SCI papers related to Voc loss analysis in the field of perovskite solar cells. It can be seen from the trend that the open circuit voltage Voc loss research has gradually attracted attention since 2015, and it has increased linearly. Although in 2019~2020, the number of papers has a stagnation period due to the Covid-19 epidemic, in 2021 there will be a doubled increase in the number of papers. According to statistics, the number of SCI papers published by May 2022 has reached the level of the whole year of 2021. It is estimated that the number of papers in 2022 will also double the number of papers compared to 2021.
As mentioned above, summarizing the research results of many outstanding scientists on the Voc loss analysis of perovskite solar cells, in terms of structure, most of the focus is on the interface between the perovskite absorber and the charge transport layer. Quantitative analysis to determine the origin of its non-radiative recombination will be of great help for the continuous breakthrough of the efficiency limit of perovskite solar cells.
Based on the above requirements, two things have naturally become the most concerned projects in the field of perovskite research: (1) How to achieve accurate measurement? (2) How to use the measurement data to quickly calculate and obtain the analysis results of thermodynamic loss (ΔE1), radiative recombination loss (ΔE2) & non-radiative recombination loss (ΔE3)? This is also a common pain point in this research field.
The Enlitech Perovskite and Organic Photovoltaic Voc Loss Analysis System (Enlitech REPS) is a complete system that can help scientists measure, calculate and analyze the Voc-loss in working solar cells and improve for the next step in the process Provide ideas. REPS can not only accurately detect extremely low EL-EQE signals (as low as 10-5 %, or 7 orders of magnitude), but also calculate thermodynamic Voc loss, radiative composite Voc loss and non-radiative composite Voc loss (through its software SQ-VLA ). In addition, it can analyze ΔV1, ΔV2, and ΔV3 losses between different types of devices in one histogram. Quickly provide researchers with effective test data and analysis results, which not only saves researchers’ time, but also avoids errors caused by human calculations.
Fig3. Enlitech Perovskite and Organic Photovoltaic Voc Loss Analysis System (Enlitech REPS)
Fig. 4. The loss analysis and improvement of perovskite solar cells are carried out using the Perovskite and Organic Photovoltaic Voc Loss Analysis System (REPS) of Guangyan Technology, and the research results produced by the system can be seamlessly integrated and quickly published in journals.
For the research on the conversion efficiency of high-efficiency silicon solar cells such as PERC, HJT, and TOP-Con, since 2015, the focus of research has been on loss analysis. Conversion efficiency losses can be attributed to three factors including short circuit current density (Jsc), open circuit voltage (Voc) and fill factor (FF) losses. The QE-RX of Guangyan Technology can not only measure PV-EQE, reflectance and PV-IQE data, but also analyze Jsc, Voc and FF loss in combination with the analysis software SQ-JVFLA. Enlitech has integrated three different test functions in the QE-RX and developed the SQ-JVFLA software to help users analyze three different losses using Shockley-Queisser thermal limit theory. QE-RX is your best partner for improving the photovoltaic efficiency of silicon solar cells.
Fig. 5. Perovskite and organic photovoltaic Voc loss analysis system of Guangyan Technology