Controlling Nucleation And Growth Of Crystal In Printing Formamidine Perovskite Solar Cells

Perovskite solar cells,as the outstanding one in the third generation of the new-type solar cells,have great prospects in the application.But its degree of commercialization is still low,and it can only be conducted in the laboratory.In order to realize the commercialization,the researchers introduced all kinds of solution processing methods in other thin film preparation,and in the end the crystallization in the period between solution and perovskite must be faced.However,it is the generation and transformation of photovoltaic phase that hinders the development of printing process.So it is the common problem in perovskite solar cells that needs to be solved.Additives are chosen to control crystallization in tin-based perovskite,the crystallinity of which is poor than other kinds of perovskite.And then the strategies are combined with the practical issue in printing to guide the improvement in printing.Firstly,through studying the roles of biomolecular in the crystallization process,additives with suitable groups are selected.However,the long-chain compounds are commonly unable to keep the perfect configuration like biological protein,so the graphene materials planar molecules with existence space continuity are chosen.The superiority can be seen from the results of graphite carbon nitride fully.And the conclusion that the size-effect can inhibit nucleation of perovskite and then delay the crystallization to improve the quality of films is brought out.This basic idea realizes that PCE of flexible tin base perovskite solar cells achieves 8.56%and guides the subsequent works.Then the strategy of additive continues to be adopted.On the one hand,benzoporphyrin derivatives with antioxidant properties are chosen to protect the crystal and passivate the films in view of the poor stability of tin-based perovskite.On the one hand the ester bond on it can interact with Sn²⁺or Pb²⁺to inhibit nucleation and then improve quality of films,through which the theory is confirmed again.The additive of nickel porphyrin also successfully improves the PCE of tin-based perovskite solar cells.Finally,in the printing process,the theory of delaying nucleation and optimizing crystallization is continued to be used and the sally port that surface energy affects the energy of nuclear in perovskite is found.Oil-soluble polyurethane is used as an additive to improve the surface energy of ink and reduce the difference of surface energy between ink and substrate.The value is derived by the theoretical formula about the nuclear power which is reduced,and the solution continues to be supersaturated so that the change of nuclear energy can effectively reduce nucleation.Thus competition of perovskite crystal growth is fully reduced.Not only the perovskite crystal becomes bigger,also makes the optimization is more apparent in the printing large-area of thin film.From the perspective of adjustment of printing process parameters,this strategy can also improve its operational tolerance,and high-quality perovskite films can be prepared even if the process parameters are optionally changed within a certain range.