| In the structure of polymer solar cells(PSCs),the charge collection layer between the active layer and the electrodes has various functions such as reducing contact resistance,optimizing the energy level between layers,and improving the light field distribution.Meanwhile,it is one of the most critical factors affecting the power conversion efficiency(PCE)and the stability of the PSCs.Among them,metal complexes have been widely used in PSCs for their advantages,including low cost,solution-processing,adjustable light field distribution,and optimizing energy levels.However,metal complexes still face different problems:low electrical conductivity,inability to adjust the internal light field of the device,and complicated manufacturing processes.Therefore,based on the acetylacetone group,a series of new metal complexes were designed and synthesized in this paper to optimize the optical field,photoelectric characteristics,and stability of PSCs,and they were applied as electron collecting layers(ECLs).Secondly,in this paper,a general method to prepare ternary blend structure by synthesizing dual-cable donor-acceptor molecules was also proposed,thus effectively expanding the absorption spectrum of the active layer and further improving the PCE of PSCs.Therefore,the main contents of this paper are as follows:1.A series of metal complexes that could form adjustable size nanoparticles were designed and synthesized,and they were also adopted as scattering centers and charge collection layers in PSCs.Metal complexes-based hafnium,including Hf(Acac)4,Hf(ACB 1)4,and Hf(ACB)4,were designed and synthesized by extending and introducing benzene rings with different amounts into the acetylacetone structure.Due to their different conjugation properties,when the three complexes were used as ECLs,they can self-assemble into nanoparticles with different sizes.Afterward,these nanoparticles distributed uniformly on the surface of the active layer can be used as the scattering center,optimizing the light field distribution,thereby significantly enhancing the light capture of the active layer.Additionally,the simulation calculation,reflection spectrum,and external quantum efficiency of different metal complexes such as ECLs displayed that PSCs with Hf(ACB1)4 can obtain the optimal optical field distribution and efficiency.Hence,based on PM6:BTP-eC9,PSCs achieved a PCE of 17.13%and good device stability.2.The crosslinkable group was introduced into the acetylacetone structure,and the ECL with the anti-solvent property was also prepared from the synthesized metal complexes.1,3-bis(4-vinylphenyl)propane-1,3-dione(ACBV)was synthesized by introducing crosslinkable functional groups into acetylacetone monomer.Simultaneously,the crosslinkable characteristics of the Hf(ACBV)4 could be proved by the measurement of differential scanning calorimetry and the UV-visible optical absorbance spectra of crosslinked films before and after being washed by chloroform.The results revealed that Hf(ACBV)4 film had excellent solvent resistance after cross-linking reaction was initiated by heating.The crosslinked Hf(ACBV)4 film could also be applied to PSCs as an ECL.The PCE of the device-based PM6:Y6 could reach 15.17%,and the efficiency could remain above 90%after continuous illumination in the air for 20 hours.It is proved that Hf(ACBV)4 could effectively improve the contact and charge transfer efficiency between ITO and the active layer and enhance the stability of the device.3.By introducing the amide group into ACB1,a novel ligand structure N-((3-oxobutyryl)phenyl)acetamide(ACBNO)based on acetylacetone was designed and synthesized,and the complex Hf(ACBNO)4 with good alcohol solubility was also obtained.The Hf(ACBNO)4 thin film can effectively absorb ultraviolet light,ranging from 300nm to 400 nm,to improve the optical stability of the device.Spinning coated Hf(ACBNO)4 on the substrate of SnO2 has excellent charge transport and high light transmittance,which could make the active layer obtain uniform surface morphology and appropriate phase separation size,after which optimizes the energy level of SnO2 to improve the open circuit voltage(VOC)and filling factors of the device.Meantime,HF(ACBNO)4 can effectively isolate oxygen and water to improve the overall stability of the device.The device with Hf(ACBNO)4 as ECL still has good overall stability after 500 hours of continuous illumination in the air,and the VOC maintains above 95%,and the PCE is also above 75%.The PCE of the device with SnO2/Hf(ACBNO)4 as the ECL could reach 15.84%,and the stability of the device with SnO2 as ECL has been greatly improved.4.A general method for developing a novel dual cable donor-acceptor material,namely ITLYBT,has the same partial molecular fragment of the donor and the acceptor has been supposed.Since the absorption spectrum of the ITLYBT molecule is the superposition of the donor skeleton and the absorption characteristic peaks of the acceptor unit,the blue shift of the characteristic absorption peak is about 200 nm due to the enhancement of steric hindrance.Therefore,ITLYBT can be used as a supplementary component of high-efficiency ternary PSCs to expand the absorption spectrum of the active layer.The devices with ternary structure presented higher short-circuit current density and open circuit voltage.The PCE of the devices also increased from 12.50%to 13.14%,which was caused by introducing ITLYBT into PBDB-T-2F:ITIC-4F blend structure,optimizing phase separation of the active layer,and reducing charge recombination.The results show that this method effectively constructs high-performance ternary PSCs via designing and synthesizing the donor-acceptor dual cable molecule.Metal complexes can also play an excellent role in the ternary structure as ECLs. |
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