Recent Progress On Perovskite Homojunction Solar Cells

Perovskite solar cell is a star of the new generation of photovoltaic technology with the greatest application potential due to its simple preparation process and rapid efficiency improvement. At present, the mainstream perovskite solar cell adopts p-i-n structure, using carrier transport materials to extract electrons and holes respectively, so as to realize electric energy output. However, the dependence of traditional p-i-n perovskite solar cell on electron transport layer and hole transport layer makes it not a cost-effective cell, and greatly increases the risk of device stability. Therefore, the design and preparation of perovskite p-n homojunction to realize carrier separation and transmission is considered as an important direction of structural innovation. In recent years, it has been reported frequently that perovskite photoelectric materials exhibit flexible conductivity from p-type, intrinsic to n-type depending on self-doping or external impurities doping. Furthermore, the perovskite p-n homojunction has been developed by a combined deposition method, which provide the possibility for designing and preparing perovskite homojunction solar cells (PHSCs). PHSCs abandon the traditional electron transport layer and hole transport layer, simplifying the device structure. It can not only improve the working stability and reduce the production cost, but also further release the application potential of perovskite solar cells in the field of flexibility and translucency, which can promote the practical popularization of perovskite solar cells. Nevertheless, the PHSCs is still in its infancy, and there are many technical problems to be solved which restrict its efficiency and stability improvement as well as its scale and industrial production. Firstly, the doping degree of perovskite materials should be further increased for high efficiency perovskite homojunction. It means that more accurate self-doping method and exogenous doping processes for heavy doping perovskite need to be developed. Secondly, the stability of the perovskite homojunction should be enhanced to promote the practical application, which requires us to start with the three aspects of inhibiting perovskite decomposition, blocking ion migration, and developing the supporting encapsulation technology to carry out relevant research programs. Thirdly, it is an important task for the industrialization of PHSCs to realize the large-scale preparation through combined deposition method, preservation transfer of perovskite films or superficial doping technology. In this paper, the research progress of PHSCs is reviewed in terms of p-type/n-type doping process and perovskite homojunction. The basic structure, working principle and existing technical problems of PHSCs are discussed in detail. This work has wide ranging impacts beyond solar cells, including emerging applications in light emission, photoelectric detector and neuromorphic computing.