Preparation And Optimization Of Photo-functional Layers Of Perovskite Solar Cell

Organic-inorganic hybrid perovskite(OIHP)has the advantages of high absorption coefficient,low exciton binding energy,adjustable optical band gap,and long electron-hole diffusion length.It has attracted extensive attention in optoelectronic devices.Due to these excellent characteristics,the power conversion efficiency(PCE)of perovskite solar cells(PSCs)has rapidly increased from 3.8%to 25.2%just a few years,which is very close to the efficiency of commercial silicon solar cells.There are many factors that affect the performance of PSCs,and the quality of the perovskite optical functional layer is very important.The perovskite optical functional layer not only plays the role of absorbing light energy but also realizes the effective transmission and separation of photo-generated carriers.The polycrystalline perovskite film obtained by low temperature solution preparation process usually has a lot of defects on the surface and grain boundaries,which leads to the reduction of photocurrent of PSCs and accelerates the decomposition of perovskite.Therefore,the perovskite optical functional layers with uniform and dense surface,large perovskite grain size and low defect density is extremely important for improving the performance of PSCs.This article focuses on how to prepare high-quality perovskite optical functional layers,using solvent vapor annealing and passivation defects to explore and study,the research content and results are as follows:(1)Solvent vapor annealing treatment of lead acetate based(PbAc2·3H2O)perovskite optical functional layer.The perovskite optical functional layer with lead acetate as the lead source is prepared by one-step solution spin coating.Comparing with the PSCs with lead iodide as the lead source,the lead acetate-based PSC has the advantages of low cost and simple preparation process.During the annealing of the perovskite optical functional layer,N,Ndimethylformamide(DMF)solvent is introduced to induce recrystallization of the perovskite optical functional layer surface,increase the grain size,and reduce the number of grain boundaries and holes.At the same time,a physical model is established to clearly show the process of solvent annealing,and the mechanism of solvent annealing to promote grain growth is analyzed.When the volume of the solvent DMF is 15 μL,the average grain size of the perovskite optical functional layer is the largest(520 nm)and the number of holes is the smallest,corresponding to the highest PCE of the device of 13.71%.(2)Acetate(PbAc2·3H2O)modified perovskite optical functional layer.A small amount of PbAc2·3H2O is added to the FA/MA/Cs perovskite precursor solution,and the acetate of PbAc2·3H2O forms a hydrogen bond with the A-site ion of the perovskite,making the perovskite mesophase more stable and conducive to slow down the crystallization process of perovskite.It not only improves the crystalline quality of the perovskite optical functional layer,but also reduces the non-radiative recombination centers formed by grain boundary defects.When the doping amount of PbAc2·3H2O is 2%,the perovskite optical functional layer has the best crystalline quality and the strongest light absorption capacity,and the PCE corresponding to the device is 20.39%.(3)Benzene sulfonate(sodium dodecylbenzene sulfonate,SDBS)passivates the defects of the perovskite optical functional layer.SDBS is composed of benzene ring,sulfonic acid group,alkyl chain and sodium ion.Firstly,ligands containing sulfonic acid groups can interact with the lead ions in the perovskite precursor,causing SDBS to adhere to the surface of the perovskite,inhibiting the growth of perovskite crystals,and improving the morphology of perovskite optical function layer.Secondly,the electron donor aromatic group may reduce the acceptor trap state caused by dissociated iodine.Sodium may fill the vacancies generated by the A site ions of perovskite,reduce carrier recombination,and help to improve carrier utilization.Finally,the long-chain alkyl group forms a hydrogen bond with the iodine in the perovskite precursor,reducing the degradation of the perovskite and helping to enhance the stability of the perovskite optical functional layer.When the SDBS concentration is 20 ppm,the corresponding device has a PCE of 20.88%,negligible hysteresis effect and better air stability.(4)Alkyl ammonium salt(didecyl dimethyl ammonium chloride,DDAC)modified perovskite optical functional layer.On the one hand,alkyl halides can act as hydrogen bond acceptors.DDAC can form hydrogen bonds with the A-site ions of perovskite,causing DDAC to attach to the perovskite crystal nucleus,promoting favorable grain orientation and suppressing the density of trap states.On the other hand,the long alkyl hydrophobic chain of DDAC can inhibit water molecules,which helps to extend the stability of the perovskite optical functional layer.When the added volume of DDAC is 1.5%,the PCE of the corresponding PSC is 20.25%,and the average PCE is 19.37%.