Thin Film Solar Cell Applications

- Jul 30, 2018-

   The sun projects more energy per hour onto the Earth's surface than the total energy used by humans throughout the world. At the same time, humans are struggling with environmental pollution, climate change, and the depletion of fossil fuels. Solar technology can solve the above problems well. The latest photovoltaic technology converts solar energy into electrical energy, which is superior to ordinary renewable energy. So why don't we use this superior technology to power our home? When asked about this question, most people give the answer that the installation cost of the photovoltaic system is too high. But the new thin film photovoltaic products are cheap and good. In the near future, this technology will change our perception of electricity and the conversion of the sun into fuel.

Solar panels are tools for continuous solar energy. We can often see rectangular solar panels on the roof, rows of solar panels in the fields and grasslands. But the kind of solar panels we know so far (1.7 meters long, 0.8 meters wide, 5 centimeters high) may be history. Because a new technology can already replace traditional silicon solar panels, it can convert solar energy into electricity efficiently and cheaply. The new technology is thin-film photoelectric conversion cells, and by 2010, they have generated 3,700 megawatts of electricity worldwide.

After 2010, thin-film solar cells have been widely used in commercial buildings and homes, and the electricity production has been further improved, from California to Kenya to China. In addition to flexibility, the following discussion will continue to discuss the advantages and disadvantages of thin-film solar cells compared to conventional solar cells, why they are more efficient, and whether thin-film solar cells can be a substitute for coal and nuclear energy.


 The application of thin film solar cells - the rise of thin film solar cells

Speaking of solar cells, currently dominated in this industry is silicon crystal, which is made of refined silicon. This module has been around the basic technology of solar energy for more than 50 years. Since the first silicon solar cell was invented in 1954, its number has increased rapidly, and currently 12% to 18% of solar radiation converted into electrical energy is achieved through it.

Crystalline silicon materials still dominate the solar photovoltaic cell materials, but in recent years there have been many breakthroughs in thin film photovoltaic technology. In 2005, crystalline silicon accounted for more than 95% of the solar cell market. However, since that time, the share of thin-film photovoltaic materials in the market has steadily increased year by year, and today it has accounted for 25%. Hundreds of companies engaged in thin film photovoltaic technology have entered a new phase of R&D and production.

Large-area and laminated thin-film photovoltaic products have been commercialized since the 1990s, and the energy conversion efficiency of thin-film photovoltaic products has reached 6% to 11%. The higher the energy conversion efficiency, the less area is needed to generate a certain amount of electricity and the other auxiliary equipment, which is a very cost-effective thing. At present, the conversion efficiency of thin film solar cells is still far from crystalline silicon, but compared with crystalline silicon, thin film solar cells have great advantages in other aspects. The most important point is that the production cost of thin film solar cells is low. Many thin film solar panels are made of amorphous silicon, and higher silicon is used to prepare silicon solar panels. In addition, thin film solar cells can be made of other semiconductor materials, including copper indium gallium selenide (CIGS) materials and cadmium telluride materials.

Thin Film Solar Cell Applications - Scaled Practical Thin Film Photovoltaic Cell Project

A key question in the field of renewable energy is when large-scale solar photovoltaic technology can compete with or be equivalent to the price of electricity from fossil fuels. In fact, large-scale thin-film photovoltaic technology is already lower in cost than nuclear power, but it is currently more expensive than burning coal.

Many thin film solar cell producers have succeeded in reducing costs, and the current leader in this field is First Solar, located in Tempe, Arizona. First Solar produced 1 GW of electricity through a cadmium telluride battery in 2009. In other words, 1 gigawatt is equivalent to the total production of 250,000 large-scale home thin-film solar photovoltaic systems.

First Solar achieved an average energy conversion efficiency of 10.9% in 2009, and their products became the most energy-efficient products in film products. The company also solved the problem of heavy metal cadmium used in production, and designed a circulatory system to prevent cadmium, a harmful substance, from being discharged along with the waste.

In the past few years, First Solar has significantly reduced their production costs. Their cost is only half that of silicon-based materials or other thin-film solar products currently on the market. Their cost reduction measures include reduced production time and installation time for large-scale equipment. Compared with other companies in the same industry, First Solar's large-scale equipment installation costs have been reduced by 10% to 15%, but their output is about 10% higher than the production of silicon crystal companies (in the same design efficiency) under). In the next five years, First Solar will focus on increasing production efficiency by another 15% and further reducing its production costs. If the company is really successful in achieving the above goals, then getting electricity from a large-scale thin-film solar installation will be as cheap as getting electricity from fossil fuels.

Can we install photoelectric conversion devices on the roof of each house?

In the future, using more large-scale thin-film solar panels will be the right step, which means more consumers can buy clean energy, but the control of energy production will still be controlled by a few large companies and municipal units. . In addition, the transfer of energy from areas with good sunlight (such as the southwest) to areas with poor light conditions requires a huge amount of money to build a power transmission network, and at the same time, the basis for storing excess electricity and then releasing it. Facilities are also essential. An alternative to concentrated energy production is to disperse production energy in different places. In addition to manufacturing large new solar panels, why don't we install solar panels in every house and parking lot? Production is carried out in a way that is zero. I firmly believe that the solar energy obtained in homes and parking lots in the United States will be enough to provide all the energy we need. In fact, some current US policies have already supported this practice.

Since thin film solar panels are very lightweight, it is feasible to incorporate them into buildings, such as making roofs. Building integrated solar panels is a new idea. In fact, architects began to use solar photovoltaic materials to make roofs in the 1980s, and the glass materials currently used to make roofs are expensive and widely questioned. The glass is light-transmissive, has a long life and is not affected by the weather, but it is fragile and is not an ideal material for making roofs.

More than a decade ago, stacked amorphous silicon thin film solar materials highlighted the advantages of using thin film solar materials to make roofs. In 2001, Solar Integrated Technologies developed a new process for converting laminated solar materials into film materials for commercial buildings. Solar Integrated Technology is one of the first companies to mass produce thin film photovoltaic cells. By 2009, a number of large companies began to enter this field.

There are many other possibilities for the application of building integrated photovoltaic materials. For example, in some cases, glass photovoltaic devices can replace conventional building materials for the manufacture of awnings and the front of houses. There are also companies producing thin film photovoltaic materials for the manufacture of windows. In addition, the development of cheap solar railway sidelines also has great potential. The emergence of every new technology will bring a lot of practical applications. Future people may wonder why we are now burning fossil fuels to get electricity. But we don't have to wait until the future, because we can now convert sunlight into electricity through thin-film photovoltaic materials.


Thin Film Solar Cell Applications - Thin Film Solar Cells

1. Amorphous silicon.

Amorphous silicon film is one of the core raw materials of solar cells, also known as microcrystalline silicon. According to different materials, current silicon solar cells can be divided into three categories: monocrystalline silicon solar cells, polycrystalline silicon solar cells and thin film solar cells. Amorphous silicon films are relative to single crystal silicon and polycrystalline silicon. As a new type of solar cell, thin-film solar cells have broad market prospects due to their wide range of raw materials, low production costs and easy mass production. Thin film batteries are basically divided into three types: non-microcrystalline silicon thin film batteries, CIGS thin film batteries and CdTe thin film batteries. Among them, GIGS has the highest conversion efficiency, about 10% to 12%, CdTe conversion efficiency is second, about 8.5% to 10.5%, and non/microcrystalline batteries are the lowest, generally 6% to 8%; In terms of accessibility, the raw material of the non-microcrystalline battery is silane, which is the most common, while the raw materials of the other two batteries contain rare element compounds, and the availability is low. In recent years, amorphous silicon thin film solar cells have gradually emerged from various types of solar cells, creating an investment boom around the world. Large-size glass substrate thin-film solar cells are on the market, which will greatly accelerate the promotion and popularization of photovoltaic building integration, rooftop grid-connected power generation systems, and photovoltaic power plants. At the same time, the amorphous silicon thin film battery is weakly attenuated under high temperature conditions, so it is also suitable for building power stations in high temperature and desert areas.

2. Copper indium gallium selenide battery board.

CIGS is a shorthand for the solar thin film battery CuInxGa(1-x)Se2, which has the advantages of good stability, good radiation resistance, low cost and high efficiency. The highest conversion efficiency of the small sample CIGS thin film solar cell was 21.7% in December 2014, and was prepared by co-evaporation by the German solar and hydrogen energy research institute ZSW. The conversion efficiency and yield of large-area battery modules vary according to the preparation process of each company, and are generally in the range of 10% to 15%. The copper indium gallium selenide thin film solar cell has the characteristics of low production cost, low pollution, no degradation, good low light performance, etc. The photoelectric conversion efficiency is the first among various thin film solar cells, close to the crystalline silicon solar cell, and the cost is a crystalline silicon battery. One-third of what is internationally called "a new type of thin-film solar cell that is very promising in the next era." In addition, the battery has a soft, uniform black appearance, which is an ideal choice for places with high requirements for appearance, such as glass curtain walls for large buildings, and has a large market in modern high-rise buildings. Although CIGS batteries have the advantages of high efficiency and low material cost, they also face three main problems: (1) complicated process and high investment cost. (2) insufficient supply of key raw materials. (3) buffer layer CdS is potentially toxic. .

3. Cadmium telluride.

CdTe is a II-VI compound semiconductor with a band gap of 1.5eV, which is very compatible with the solar spectrum. It is most suitable for photoelectric energy conversion. It is a good PV material with high theoretical efficiency (28%) and stable performance. It has always been valued by the photovoltaic industry and is a thin film battery that has developed rapidly in technology. Cadmium telluride is easily deposited into a large-area film and has a high deposition rate. CdTe thin film solar cells are the easiest to manufacture in solar cells, so it is the fastest growing commercialization. To improve efficiency, it is necessary to optimize the structure of the battery and the material of each layer. Appropriately reduce the thickness of the window layer CdS, which can reduce the loss of incident light, thereby increasing the short-wave response of the battery to improve the short-circuit current density, and the CdTe battery with higher conversion efficiency A thinner CdS window layer was used to set a record. To reduce costs, it is necessary to reduce the deposition temperature of CdTe below 550 ° C to suit the cheap glass as the substrate; laboratory results must go through the design, research and optimization of components and production models.

4. Organic thin film solar cells.

Organic solar cells, as the name suggests, are solar cells that are made up of organic materials. The organic material having photosensitive properties is mainly used as a material of a semiconductor, and a voltage is generated by a photovoltaic effect to form a current, thereby realizing the effect of solar power generation. Organic thin-film solar cells have significant advantages such as low potential price, easy processing, large-area film formation, designability of molecular and film properties, light weight, flexibility, etc., but organic semiconductors have lower carrier mobility than inorganic semiconductors. Poor stability. At present, the photoelectric conversion efficiency of organic solar cells is very low, and it is only possible to increase the photoelectric conversion efficiency to more than 5%.