In recent years, organic-inorganic hybrid perovskite solar cells have been widely concerned.The material has the advantages of adjustable bandgap, high absorption coefficient, long carrier lifetime and high carrier mobility.Porovskite solar cells have been reported The highest efficiency has more than 20% Recently, the Chinese Academy of Sciences, Chinese Academy of Sciences Institute of semiconductor semiconductor materials science laboratory Wang Zhanguo group, in the perovskite solar cell carrier transport management research has made new progress.
The organic-inorganic hybrid perovskite material as the active layer plays a key role in the cell efficiency, and the pure perovskite thin film to improve the efficiency of the battery has been at the bottleneck.This requires the physical process of photoelectric conversion, the battery structure In this context, the team constructed a typical P-I-N structure and systematically studied the factors affecting the generation and separation of photoexcitation excitons and the transport and collection of carriers in perovskite solar cells.
1, the mechanism of the cathode work function
The difference between the work function of the electrode and the Fermi level of the active layer influences the band bending and the interfacial dipole moment, which has an important influence on the carrier transport. The typical inverted perovskite solar cell is used to control the metal buffer The work function of the layer adjusts the energy band bending at the interface of the active layer of the cell, which facilitates the transport and collection of electrons, thereby promoting the generation and separation efficiency of photogenerated excitons. The research is published in Small and the research work is supported by the Ministry of Science and Technology Funding for Key Basic Research Development Program (973 Program).
2, carrier transport management
A highly efficient inverted-structure perovskite solar cell is designed from the perspective of efficiently separating, transporting and collecting photo-generated carriers.The electron mobility of PC61BM is improved by modifying Al electrode with zirconium acetylacetonate (ZrAcac), and the density of defect states is reduced. For the battery charge transport resistance is reduced to achieve the cathode efficient collection of electrons; the use of Cu doping NiOx hole transport layer optimization, the presence of Cu can enhance the NiO xLayer hole mobility, while Cu doping NiO can be adjusted xOf the energy level position, in the case of the smallest open-circuit voltage loss, to achieve the purpose of hole transport; the use of high conductivity FTO glass substrate can be avoided in the NiO xAnnealing caused by the decline of the anode conductivity, the battery charge transport resistance to further reduce the battery fill factor to improve the battery's photoelectric conversion efficiency of 20.5%. The results published in Energy & Environmental Science, the research has been the Ministry of Science and Technology Funding of National Key Basic Research and Development Program (973 Program).
Figure 1. (a) Jph versus Veff for different cathodic work function cells, inset for Gmax values of corresponding cells (b) P (E, T) versus Veff for different cathodic work function cells, Short-circuit current state, the corresponding battery P (E, T)
Figure 2. IV curve and band structure of perovskite solar cell (left), SEM image of cross section of perovskite solar cell (right).
