In recent years, CH 3NH 3PbI 3As the representative of the perovskite crystalline organometallic halide in the field of optoelectronics has attracted a great deal of research interest.
As a new semiconductor photoelectric conversion material, it has a high extinction coefficient (105 cm -1), Long carrier lifetime (~ μs), low defect concentration, low exciton binding energy and low cost solvent preparation, etc. Photoelectric conversion of thin film solar cells (perovskite solar cells) based on this kind of material Its efficiency exceeds 22%, surpassing that of polycrystalline silicon solar cells and has a good prospect of application. At the same time, the material shows good performance in photoelectric detection, light emission, high energy ray detection and nonlinear optics, (Device) physical and chemical cross-cutting areas of research focus.Chinese researchers in the efficient non-hole-transporting materials and devices, the exploration and application of new materials, material preparation, physical and chemical process control, large area device development, device stability and high efficiency Light and so have made a positive contribution.
Based on the current research status of perovskite thin-film batteries, a team headed by Meng Qingbo, a researcher at the Institute of Physics, Chinese Academy of Sciences, recently published a paper entitled "Inorganic-organic halide perovskites for new photovoltaic technology" in the National Science Review (2017) Of the paper, from the structural characteristics of the perovskite material, material preparation techniques and key physical properties of such materials and devices for the development are reviewed and discussed.
This dissertation focuses on and discusses the key physical properties of perovskite materials such as semiconductor doping, junction electric field, defect state, ion migration and the evolution of semiconductors induced by them. The theoretical studies show that the self-doping of ternary perovskite materials (Such as atomic deletions, gaps and substitutions) can induce the generation of p-type or n-type carriers.At present, experimental control of the type of perovskite charge carriers has been initially conducted through the physicochemical processes that control the deposition of thin films, such as : In the two-step method, the hole concentration of methylamine and lead iodine is controlled.In addition, the p-type carriers expected from heterojunction cells can also be obtained by heteroatom doping.Based on the p-type Doping, unilateral heterojunction existing between TiO2 / perovskite absorption layers can be observed in n-TiO2 / perovskite / hole transport layer structures, and the depletion region is mainly distributed in the region of calcium However, no junction was observed between the perovskite layer and the hole transport layer, indicating that the perovskite cell is more likely to be a single heterojunction cell rather than a conventional pin-type cell. With regard to the deep defect level of this type of material, A variety of methods have been used to measure the results, indicating that this low-temperature solution prepared perovskite thin film material concentration can be as low as 1015 cm-3, thus ensuring a long carrier lifetime .Recently, theory And experimental measurements show significant ion migration in this type of material, and ion migration leads to material doping and redistribution of defect states, which in turn affects the optoelectronic process and stability of the device.
The understanding of these key physical properties is of great importance for the performance improvement of the perovskite devices and for the development of new applications and is also the basis for the correct evaluation and recognition of the core issues of perovskite devices.For perovskite devices the lower stability Is one of the bottlenecks of its further development. The stability of the physical properties is the key point and deserves in-depth attention.
