Popularization of knowledge about solar photovoltaic power generation

Cutting-edge silicon technology

Since 2006, crystalline silicon modules have accounted for more than 80% of the global photovoltaic application market clock, occupying a dominant position in photovoltaic applications. As the mainstream crystalline silicon photovoltaic technology in the current photovoltaic market, it has also been seeking breakthroughs in conversion efficiency. From double-glass modules, high-efficiency photovoltaic modules to concentrated photovoltaics, technology has been iterating forward. The following is a detailed introduction to several emerging crystalline silicon photovoltaic technologies.

1. N-type high-efficiency single crystal photovoltaic cell technology

The N-type single crystal high-efficiency cells currently researched mainly include: PERT cells, PERL cells, HIT cells, IBC cells, HBC cells, etc. According to the light-receiving surface of the battery, it is divided into single-sided light-receiving type and double-sided light-receiving type. The efficiency of a 6-inch large-area IBC cell independently developed by a national key laboratory of Changzhou Trina Solar Photovoltaic Science and Technology has reached 22.9%, becoming the highest conversion efficiency of a 6-inch IBC cell. The N-PERT small-area battery (4cm2) prepared by the Fraunhofer laboratory in Germany using PassDop technology, its conversion efficiency can reach 23.2% (Voc=699mV, Jsc=41.3mA/cm2, FF=80.5%); the continuous pursuit of efficiency improvement and Cost reduction is the eternal theme of the photovoltaic industry. Compared with traditional P-type crystalline silicon cells, N-type crystalline silicon cells have greater space and potential for efficiency improvement due to their natural advantages such as no light-induced attenuation. It is the technical route for high-efficiency cells. It is an inevitable choice, and with the introduction of new battery technologies, the efficiency advantage of N-type crystalline silicon cells will become more and more obvious.

2. Concentrating photovoltaic cell technology

Concentrated solar energy is a solar power generation technology that uses optical elements such as lenses or mirrors to concentrate a large area of sunlight on a very small area, and then further utilizes to generate electricity. CPV is the most typical representative of concentrated solar power generation technology. In 2014, Fraunhofer and its partner French Soitec and its French research institute CEA-Leti created a concentrating solar cell with a photoelectric conversion efficiency of up to 46%, which is the highest photoelectric conversion efficiency record, demonstrating its industrial application potential.

二. Cutting-edge thin film technology

Thin-film solar cells can be manufactured using inexpensive ceramics, graphite, metal sheets, and other different materials as substrates. The thickness of the thin-film solar cells that can generate voltage is only a few μm, and the production cost is lower. Thin-film solar cell technology is ushering in technological innovation, with a rapid development momentum.

1. Compound thin-film solar cells

CIGS (Copper Indium Gallium Selenide) Thin Film Solar Cells

CIGS thin-film solar cells are chalcopyrite crystalline thin-film solar cells with the best ratio of four elements: Cu (copper), In (indium), Ga (gallium), and Se (selenium). It is the key technology for composing solar panels. A few weeks ago, the Bavarian Solar Energy and Hydrogen Energy Research Center in Stuttgart, Germany obtained the optimal energy conversion rate of CIGS (copper indium gallium selenide) thin-film solar cells. This solar cell with a size of only 0.5 square centimeters has a conversion rate of 22.6 %. Therefore, researchers at the Bafu State Solar Energy and Hydrogen Energy Research Center surpassed the previous record of 22.3% in Japan and became the new record holder. CIGS (Copper Indium Gallium Selenide) thin film solar cells have the advantages of strong light absorption, high power generation stability, low production cost, and short energy recovery period.

Cadmium Telluride (CdTe) Thin Film Photovoltaic Cells

The cadmium telluride thin film cell is a solar cell based on the heterojunction of p-type cadmium telluride (CdTe) and n-type cadmium sulfide (CdS). It is a photovoltaic device formed by sequentially depositing multiple layers of thin films on glass or other flexible substrates. Compared with other solar cells, the structure of cadmium telluride thin film solar cells is relatively simple. Generally speaking, the cell consists of five layers, namely glass substrate, transparent conductive oxide layer (TCO layer), and cadmium sulfide (CdS) window layer. , cadmium telluride (CdTe) absorber layer, back contact layer and back electrode.

The theoretical photoelectric conversion efficiency of cadmium telluride thin film solar cells is about 28%. On February 5, 2015, First Solar, one of the world's leading solar photovoltaic module manufacturers, announced that its cadmium telluride (CdTe) solar cell conversion efficiency reached 21.5% , refresh history. Since 2011, this is the eighth time that CdTe efficiency has significantly set a world record. High-efficiency and inexpensive cadmium telluride (CdTe) thin-film solar cells are increasingly used due to their inherently good material properties and their own practices. It is likely to become one of the mainstream products of photovoltaic cells in the future.

2. Organic compound thin film photovoltaic cells

In recent years, new organic compound thin-film solar cells represented by GaAs, GaAb, GalnP, Culnse2, etc. have achieved high photovoltaic conversion efficiency. The conversion efficiency of GaAs cells has now reached 30%, while Gu, ln, etc. are relatively rare. Element, Cd, etc. are toxic elements, therefore, the development of this type of battery will inevitably be limited by resources and the environment. Therefore, organic thin-film solar cells with stable condensed states have attracted much attention; their outstanding advantages, such as potential low cost, light weight, flexibility and ease of processing, and low-cost large-area fabrication, make them highly competitive.

三. Other cutting-edge technologies for power generation

In the solar cell family, there are many other new materials and technologies used in them, such as solar cells made of trees, multi-junction solar cells made of B, Al, Ga, In semiconductor materials, etc. Xiaogu selects several new power generation technologies with relatively mature technologies and high conversion efficiency to introduce to users.

1. Polymer solar cells

In 1992, Professor Alan J. Heeger's group discovered the existence of ultrafast charge transfer between conjugated polymers and fullerenes, and in 1995 realized the polymer/fullerene derivative PCBM bulk heterojunction solar energy prepared by solution. Battery. Since then, in the past 20 years, people have successively focused on the design and synthesis of conjugated polymer light-absorbing materials, the working mechanism of the device, the regulation of the morphology of the active layer and the electron-donor-acceptor phase separation behavior, the influence of the interface layer and low A lot of research has been done on cost device technology and many other breakthroughs have been made. Among them, scientists from Linköping University in Sweden and the Chinese Academy of Sciences (CAS) have cooperated to combine PBDB-T polymer and ITIC small molecules, so that the solar energy conversion efficiency reaches 11%, setting a new record for fullerene-free polymer solar photovoltaic cells. more than the vast majority of polymer solar cells.

2. Perovskite solar cells

The rapidly developing perovskite cells have been a research hotspot in the solar energy industry in recent years. Below are three large-area solar cells fabricated from 2D perovskite materials: room temperature cast film on the left; problematic bandgap sample on the upper middle; hot cast sample with optimal energy performance on the right .

Perovskite cells have the advantages of low cost and simple process (applicable to various industrial technologies, including solution operation, roll-to-roll processing, thermal evaporation, etc.), but the development of perovskite cells also faces severe challenges: The bottleneck of natural environment stability, as well as key technical issues such as Pb toxicity, environmental pollution and material recycling. Recently, the State Key Laboratory of Fine Chemicals of Dalian University of Technology has solved this problem: this type of battery has achieved the highest photoelectric conversion efficiency based on carbon counter electrodes.

The new generation of perovskite cells that were born, as one of the "top ten scientific and technological breakthroughs in the world", have achieved an efficiency of more than 22.1% in just four years, which has greatly challenged traditional photovoltaic technology.

3. Inorganic nanocrystalline solar cells

Inorganic nanocrystalline solar cells were studied by Georgia Tech professor Bernard Kipren and Purdue University School of Materials Science and Engineering associate professor Jeffrey Youngblood. Their findings open a new door to the search for truly recyclable, sustainable, and renewable solar cell technologies. They use cellulose nanomaterials made of wood as substrates, which are environmentally friendly, renewable and sustainable. It is believed that in the next few years, their team can increase the power conversion efficiency to more than 10%.