Perovskite solar cells: Scientists have found in recent research that the conversion efficiency of a perovskite-structured organic solar cell can reach 50%, which is twice the conversion efficiency of solar cells. currently on the market. , can significantly reduce the cost of solar cells. Relevant research has been published in the latest issue of the journal Nature.
Disadvantages of organic photovoltaic cells
Organic solar cells have more advantages among the different technologies used by humans to use solar energy, solar cells use the “photovoltaic effect”. "Devices that directly convert light energy into electrical energy are currently widely used and are one of the most promising technologies. For a long time, people have mainly prepared solar cellss based on inorganic materials such as crystalline silicon. However, this type of battery production has disadvantages such as complex process, high cost, high energy consumption and high pollution. The question of whether we can find a new low-cost, high-efficiency, flexible and environmentally friendly organic material to develop new solar cells is now a goal that scientists around the world are striving to achieve. "Using the most abundant carbon materials on earth as basic raw materials and obtaining high-efficiency, low-cost green energy by technical means are of extremely great importance for solving major energy problems facing the world. "humanity is currently facing," Chen Yongsheng explained. started in the 1970s, research into organic electronics and functional materialsOrganic materials (polymers) offer opportunities for achieving this goal.
Compared with inorganic semiconductor materials represented by silicon, organic semiconductors have many advantages such as low cost, material diversity, adjustable functions and printing preparation flexible. At present, displays based on organic light-emitting diodes (OLEDs) have been produced commercially and are widely used in mobile phone and television screens. Organic solar cells based on organic polymer materials as a photosensitive active layer have the advantages of various material structures, low-cost large-area printing and preparation, flexibility, translucency and even total transparency. They have many advantages that inorganic solar cell technology does not offer.not. to have. In addition to being used as a normal power generation device, it also has huge application potential in other fields such as energy-saving building integration, wearable devices, etc., which has aroused great interest in the academic and industrial world. “Especially in recent years, research on organic solar cells has made rapid progress, and the efficiency of photoelectric conversion has been continuously improved. At present, the scientific community generally believes that organic solar cells have reached the "dawn" of commercialization. "said Chen Yongsheng.
At present, organic solar cells have low conversion efficiency and short lifespan. They have not yet entered the phase of use. They suffer from low mobility of the carriers, a disordered structure, a rHigh volume resistance and low battery durability. The main reasons for the poor performance of organic solar cells are:
(1) Due to the weak intermolecular interaction of organic materials, most of them are amorphous even if they are crystalline. crystalline. Due to the mixing of shapes, the photogenerated carriers generated after light irradiation mainly move on the conjugated valence bonds within the molecule. Charge transfer is achieved by carrier hopping between adjacent molecular states. As a result, the carrier mobility of organic materials is generally very low, several orders of magnitude lower than that of inorganic materials, which has a greater impact on the efficiency of organic semiconductor devices;
(2) Organic Semiconductor materials do not absorb sunlight over a wide band. The bandMaximum absorption of most materials is between 350 nm and 650 nm. However, the energy of sunlight that can be absorbed by the Earth's surface is mainly distributed between 600 nm and 800 nm. the spectrum does not match the spectrum of sunlight, resulting in low photoelectric conversion efficiency. If light absorption is improved by increasing the thickness of the active layer, this will also increase the series resistance of the device, increase the migration distance of excitons and carriers, and reduce the short circuit current, resulting in a lower photoelectric conversion efficiency;
(3) After absorbing sunlight, organic semiconductors will produce bonded hole-electron pairs – “excitons”. Not all exciton migration is efficient. First, their diffusion distance is short, usually only about 10 nm. Second, the ratetransmission of electrons and holes generated after exciton separation is not high in general organic materials. the recombination of electrons and holes, and the transmission of electrons and holes. There is usually a potential barrier that must be overcome when entering the electrode surface. In this way, there is an inevitable loss of exciton recombination during exciton migration in the semiconductor film. . Generally, only the excitations closest to the boundary or node generate photovoltaics. The current makes the actual conversion efficiency of organic solar cells low;
(4) Organic semiconductor materials are often unstable in the presence of oxygen and oxygen. water.