Classification of solar Batteries - third generation solar Batteries
1. Dye-sensitized solar Batteries
DSSCs are a class of Batteries that simulate the principle of green plant photosynthesis to convert sunlight energy into electricity. Liquid DSSCs are mainly composed of photoanode, liquid electrolyte and photocathode. The photoanode mainly prepares a layer of porous semiconductor film on the conductive substrate material and attaches a layer of dye photosensitizer; the photocathode mainly prepares a layer of platinum or carbon-containing catalytic material on the conductive substrate material. In the photoanode, the electrode material is mainly TiO2. When a layer of dye photosensitizer with good light absorption properties is attached to the surface of TiO2, the ground state of the dye absorbs light and becomes an excited state, and then the excited state dye injects electrons into the conduction band of TiO2. The separation of the carriers is completed, and it is transmitted to the counter electrode through the external circuit. The 3- in the electrolyte solution gets electrons on the counter electrode and is reduced to I-, and the oxidized dye after electron injection is turned into the ground state by I-. I- itself is oxidized to I3-, thus completing the whole cycle.
DSSCs have the advantages of simple synthesis and a wide range of material sources, but most DSSCs use liquid electrolytes, which are prone to electrode corrosion, electrolyte leakage, and poor battery stability. In response to the above problems, researchers have made some progress in developing pure organic sensitizers and solid-state DSSCs. For DSSCs, the reason why the efficiency is difficult to improve is that the existing dye sensitizers cannot effectively utilize infrared photons, resulting in low light absorption efficiency. Therefore, the focus of future research will be to develop efficient, stable, inexpensive, non-ruthenium-based dye sensitizers that respond to near-infrared light. In addition, improving the electron transport capacity inside the battery, preparing high-efficiency and durable solid-state electrolytes, finding inexpensive non-Pt counter electrodes, and improving the overall service life of the battery are also of great significance for the promotion of DSSCs.
2. Perovskite Solar Batteries
The rise of PSCs stems from the development of DSSCs, the difference is that PSCs use perovskite-type organic/inorganic hybrid materials instead of organic dye molecules as light-absorbing materials. PSCs are composed of nanocrystalline dense layer, perovskite active layer ABX3 (X=Cl-, Br-, I-), hole transport layer and counter electrode. The light absorbing layer ABX3 has a typical three-dimensional structure. A represents an organic amine ion (CH3NH3+) occupying the body center of a cuboctahedron; B represents a metal cation that can coordinate to form an octahedron, such as Pb+, Nb+, Ti4+, Fe3+, etc.; X represents an anion that can coordinate with B to form an octahedron, generally Cl-, Br-, I- and other halogen ions. The halogen octahedra in this type of perovskite material are co-top connected to form a stable three-dimensional network structure. The preparation methods of perovskite materials mainly include solution method, co-evaporation method, gas-phase assisted solution method and intramolecular exchange method.
Since the introduction of PSCs, the photoelectric conversion efficiency has increased at a nearly linear rate, showing the great potential of such Solar Batteries. Despite the high efficiency of PSCs, the stability is extremely poor. For this reason, scientists seek a variety of methods to solve the stability problem. The surface of PSCs device is coated with a layer of fluorinated photosensitive polymer by light-induced radical polymerization at room temperature. This layer of multifunctional coating material endows the front part of the PSCs device with self-cleaning and luminescent properties, and ensures that the backside of the PSCs device has superhydrophobic properties, which does not allow the surface of the PSCs device to be superhydrophobic. Influenced by water vapor in the air. Under visible light conditions, the photopolymer re-emits UV light, making PSCs as high as 19% efficient under standard illumination. Tests were carried out for 6 months under the conditions of air environment and photochemical influence, and the results showed that the photoelectric properties of PSCs were well maintained in all aspects, indicating that the performance of this type of Solar Batteries is steadily improving. Therefore, the future work should be to standardize the working standards of this type of battery, such as stability specifications, aging test standards, etc. With the advancement of technology, PSCs may surpass thin-film Solar Batteries and become a rookie in the photovoltaic industry.
3. Quantum dot Solar Batteries
Quantum dots are zero-dimensional nanomaterials, which means that the three dimensions of quantum dots are all smaller than the de Broglie wavelength of excitons of bulk materials. The movement of its internal electrons in all directions is constrained, that is, the quantum confinement effect is particularly pronounced. Compared with traditional bulk materials, the advantage of quantum dots is that through the resonance tunneling effect, it can improve the collection rate of photogenerated carriers in the battery, thereby increasing the current; by adjusting the size and shape of the quantum dots, the energy level of the quantum dots is optimized and The matching of the solar spectrum increases the light absorption rate. Some quantum dots (such as PbSe) can absorb one high-energy photon to generate multiple electron-hole pairs, that is, the multi-exciton effect. The theoretically predicted efficiency of single-junction QDSCs can reach 44%, far exceeding the Shockley-Queisser limit of silicon Solar Batteries.
Since its inception, quantum dots have shown their unique advantages, such as a wide range of material sources, adjustable band gaps, and high photoelectric conversion efficiency, all of which indicate that QDSCs have great potential. However, because this type of battery involves the micro-scale field, the manufacturing process and requirements are relatively high, and the internal electron transport principle is still in the research stage, resulting in its efficiency far lower than other types of batteries. But this type of battery has unparalleled potential of other batteries. For this type of Solar Batteries, the current research focuses mainly on material selection, device optimization, and internal electron transport mechanism in order to improve the efficiency and stability of QDSCs.
After more than half a century of development and improvement, crystalline silicon Solar Batteries have high efficiency and stability. For a long time in the future, crystalline silicon Solar Batteries will still dominate the solar photovoltaic industry. The focus of future work is mainly to simplify the Solar Battery fabrication process and reduce the Battery manufacturing cost, so as to facilitate the further promotion of crystalline silicon Solar Batteries. At the same time, scientists have also developed a variety of thin film solar Batteries, such as GaAs, CdTe, CTGS thin film Solar Batteries and so on. Compared with crystalline silicon solar batteries, the production cost of thin film solar batteries is greatly reduced, and the efficiency is getting closer and closer to that of crystalline silicon solar batteries. However, most thin film solar batteries contain rare or toxic elements, which leads to their safety problems. Commercial The chemical module still needs to be corrected and inspected, so the follow-up work needs to further improve the process (such as doping, etc.), improve efficiency, reduce production costs, and improve stability. Compared with the previous two types of solar batteries, the third-generation solar batteries have higher application prospects and development potential, but due to their involvement in the microscopic field, the fabrication process and requirements are more complicated, and the interfacial charge transport mechanism needs to be further explored.