Interfacial Modification Of Organic Conjugated Ionic Salts In Perovskite Solar Cells

Perovskite solar cells have been developed rapidly in recent years due to their unique properties.However,in order to achieve commercial applications,the efficiency and stability of the devices need to be further improved.Due to the polycrystalline nature of the perovskite film,there are a large number of defects at the grain boundary and surface,and these defects seriously affect the efficiency and stability of devices.In order to solve these problems,this article mainly conducts research from two aspects of interface engineering and additive engineering to realize all-round control of perovskite defects.On the one hand,organic interface materials have the advantages of good film-forming properties,easy preparation and adjustable energy levels,and have attracted the attention of more and more researchers in recent years.However,traditional hole transport materials such as poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid(PEDOT:PSS)have relatively few researches on the defect passivation of perovskite,and the efficiency and stability of the device are still low.On the other hand,a large number of additives are used to solve the defect problem of the perovskite light absorption layer,but the application of pure bromine perovskite solar cells is extremely rare.The work of this thesis is carried out in inverted perovskite devices,which have the advantages of low cost,simple preparation,and low hysteresis.First,a hole transport material with good hole transport ability was designed and synthesized,and it was applied to the MAPbI3 system perovskite solar cell,which finally improved the efficiency and stability of the device at the same time.Secondly,through the use of trimethylolpropane ethoxy triacrylate(TET)additive with crosslinking effect to regulate the growth of perovskite film,passivate perovskite grain boundary defects,and improve the efficiency of solar cells.The specific contents are as follows:(1)The conjugated polyelectrolyte PTPADT-SO3Na with bithiophene and triphenylamine as the conjugated organic framework and sodium sulfonate as the side chain was designed and synthesized,and used as a hole transport layer in MAPbI3 perovskite solar cell.The device improves the efficiency and stability of the device by adjusting the interface characteristics,film morphology and defect states.Compared with PEDOT:PSS,PTPADT-SO3Na has a lower HOMO level and a higher open circuit voltage.Due to the strong self-doping effect,PTPADT-SO3Na has a good hole transport ability.The results indicate that the perovskite film based on PTPADT-SO3Na is more uniform and dense,with fewer defects.In the end,we got an inverted device with a PCE of 18.15%.In addition,the dense perovskite film also helps to block the penetration of water and oxygen,and the environmental stability and thermal stability of unpackaged devices are improved.(2)For the first time,small organic molecules that can be cross-linked were used as additive TET in pure FAPbBr3 perovskite solar cells,which greatly improved the efficiency of the devices,and the highest PCE reached 8.93%.The TET molecule can be cross-linked under the annealing conditions and form a network around the perovskite grains,which slows down the crystal growth rate of the film,thereby producing large-sized grains.At the same time,the carbonyl group in the TET molecule can coordinate with the perovskite,passivate the defects,and inhibit the recombination of carriers in the device.Finally,the addition of TET also improves the open circuit voltage,short circuit current and fill factor of the device.