Application And Research Of Condensed Ring Coplanar Molecules In Perovskite Solar Cells

Perovskite solar cells(PSCs)have developed rapidly in recent years because of their high performance,low cost and simple process.However,the researchers found that their outstanding problems of poor stability,operating environment,and high cost have not been solved well,so it is still a difficult problem to cheaply prepare stable and efficient perovskite solar cells.The hole-transporting materials(HTMs)is regarded as one of the important directions for optimizing PSCs because of its huge role in carrier migration.Heteroatom-containing fused ring coplanar molecular materials are hole-transporting materials.Their synthesis is simple and inexpensive,with good intrinsic mobility and energy levels matching perovskite solar cells.Their hydrophobicity and wettability with the perovskite solution can also be adjusted based on the changes of functional groups.This subject intends to use a series of condensed ring coplanar molecular materials as the HTMs of PSCs to study their application in devices of PSCs including devices with inverted planar structure(p-i-n)and regular planar structure(n-i-p).Accordingly,this subject has done the following work:The application and optimization of the new heteroatom-containing condensed ring coplanar molecular materials named ZFDM1,ZFDM2 and ZFDM3 in PSCs with inverted planar structure(p-i-n).The optimized parameters include: the concentration of the new cavity material,the thickness of the perovskite active layer and the annealing temperature.The highest photoelectric con version efficiencies of the devices made with ZFDM1,ZFDM2 and ZFDM3 materials were 17.96%,17.81% and 16.49%.According to the experimental results,we give the general optimization process of lead-based halogen organic-inorganic hybrid perovskite solar cell inverted planar structure(p-i-n)devices.At the same time,by detecting the surface morphology of the device and the photoelectric characterization results,the internal mechanism in which various factors affect the performance of the device is described.Experimental results show that higher mobility and better energy level matching with perovskite make ZFDM1,ZFDM2 and ZFDM3 materials have higher fill factor and open circuit voltage than PEDOT: PSS.Besedes,the better light absorption characteristics can increase the short-circuit current density.The Cl atoms in the synthesis process of the new material have better hydrophilicity,and the removal of Cl atoms can increase the hydrophobicity of the film and improve the stability of the device.The application and optimization of new heteroatom-containing condensed ring coplanar molecular materials named ZFDM4 and ZFDM5 in PSCs with regular planar structure(n-i-p).Optimization parameters include the concentration of the new cavity material and the thickness of the perovskite active layer.ZFDM4 and ZFDM5 materials produced the highest efficiency of the positive devices were 9.45% and 18.84%.We give the general optimization process of small molecular materials on regular structure devices(n-i-p).Furthermore,we characterize and analyze the performance differences brought about by different molecular structures.The introduction of heteroatoms greatly increases the hydrophobicity and oxidation resistance of the device,both of which exhibit good device stability.The PSCs made with ZFDM4 and ZFDM5 as the hole transport layer still retains 78% and 90% of the initial efficiency after 20 days.The test results of PL and TRPL also reasonably explain the difference in device performance between the two device s.The relative strength of the PL of the device made by ZFDM5 is weak,which means that the hole extraction speed is faster.Furthermore,we used electrochemical impedance spectroscopy to analyze the interface electrical properties of perovskite solar cel l devices from the interface level.Compared with ZFDM4,the regular planar structure(n-i-p)device fabricated with ZFDM5 exhibits a semi-circle with a high radius in a small radius and a semi-circle with a low radius in a large radius.This result indicates that the charge transfer resistance at the internal interface of the device fabricated by ZFDM5 is smaller and the charge transfer is easier.At the same time,the recombination resistance is large,the carrier recombination is more difficult.So their devices have better performance.Those synthesis of new HTMs are simple and cheap.The performance of the prepared devices in PSCs is efficient and stable.They can also be used in devices of various structures.This research also provides some experience for the application of new small molecular materials in PSCs.