Perovskite solar cell

A perovskite solar cell (PSC) is a type of solar cell which includes a perovskite structured compound, most commonly a hybrid organic-inorganic lead or tin halide-based material, as the light-harvesting active layer. Perovskite materials, such as methylammonium lead halides and all-inorganic cesium lead halide, are cheap to produce and simple to manufacture. A perovskite solar cell (PSC) is a type of solar cell which includes a perovskite structured compound, most commonly a hybrid organic-inorganic lead or tin halide-based material, as the light-harvesting active layer. Perovskite materials, such as methylammonium lead halides and all-inorganic cesium lead halide, are cheap to produce and simple to manufacture. Solar cell efficiencies of devices using these materials have increased from 3.8% in 2009 to 25.2% in 2019 in single-junction architectures, and, in silicon-based tandem cells, to 28.0%, exceeding the maximum efficiency achieved in single-junction silicon solar cells. Perovskite solar cells are therefore the fastest-advancing solar technology to date. With the potential of achieving even higher efficiencies and very low production costs, perovskite solar cells have become commercially attractive. Metal halide perovskites possess unique features that make them useful for solar cell applications. The raw materials used, and the possible fabrication methods (such as various printing techniques) are both low cost. Their high absorption coefficient enables ultrathin films of around 500 nm to absorb the complete visible solar spectrum. These features combined result in the possibility to create low cost, high efficiency, thin, lightweight and flexible solar modules. The name 'perovskite solar cell' is derived from the ABX3 crystal structure of the absorber materials, which is referred to as perovskite structure. The most commonly studied perovskite absorber is methylammonium lead trihalide (CH3NH3PbX3, where X is a halogen atom such as iodine, bromine or chlorine), with an optical bandgap between 1.5 and 2.3 eV depending on halide content. Formamidinum lead trihalide (H2NCHNH2PbX3) has also shown promise, with bandgaps between 1.5 and 2.2 eV. The minimum bandgap is closer to the optimal for a single-junction cell than methylammonium lead trihalide, so it should be capable of higher efficiencies. The first use of perovskite in a solid state solar cell was in a dye-sensitized cell using CsSnI3 as a p-type hole transport layer and absorber.A common concern is the inclusion of lead as a component of the perovskite materials; solar cells based on tin-based perovskite absorbers such as CH3NH3SnI3 have also been reported with lower power-conversion efficiencies. In another recent development, solar cells based on transition metal oxide perovskites and heterostructures thereof such as LaVO3/SrTiO3 are studied. Rice University scientists have discovered a novel phenomenon of light-induced lattice expansion in perovskite materials. In order to overcome the instability issues with lead-based organic perovskite materials in ambient air and reduce the use of lead, perovskite derivatives, such as Cs2SnI6 double perovskite, have also been investigated. Perovskite solar cells hold an advantage over traditional silicon solar cells in the simplicity of their processing and their tolerance to internal defects. Traditional silicon cells require expensive, multi-step processes, conducted at high temperatures (>1000 °C) in a high vacuum in special clean room facilities. Meanwhile, the organic-inorganic perovskite material can be manufactured with simpler wet chemistry techniques in a traditional lab environment. Most notably, methylammonium and formamidinium lead trihalides, also known as hybrid perovskites, have been created using a variety of solvent techniques, such as spin coating, slot-die coating, blade coating, spray coating, inkjet printing, and screen printing, electrodeposition, and vapor deposition techniques, all of which have the potential to be scaled up with relative feasibility except spin coating. The solution-based processing method can be classified into one-step solution deposition and two-step solution deposition. In the one-step deposition, a perovskite precursor solution that is prepared by mixing lead halide and organic halide together, is directly deposited through various coating methods, such as spin, spray, blade, and slot-die coating, to form perovskite film. One-step deposition is simple, fast, and inexpensive but it’s also more challenging to control the perovskite film uniformity and quality. In the two-step deposition, the lead halide film is first deposited then reacts with organic halide to form perovskite film. The reaction takes time to complete but it can be facilitated by adding Lewis-bases or partial organic halide into lead halide precursors. In two-step deposition method, the volume expansion during the conversion of lead halide to perovskite can fill any pinholes to realize a better film quality. The vapor phase deposition can also be categorized into physical vapor deposition (PVD) and chemical vapor deposition (CVD). PVD refers to the evaporation of a pervoskite or its precursor to form a thin perovskite film on the substrate, which is free of solvent. While CVD involves the reaction of organic halide vapor with the lead halide thin film to convert it into the perovskite film.