Photoelectric Property Reaserch On Indium/zinc Coordination Polymer Modified Perovskite And Hole Transport Layer

In recent years,perovskite solar cells(PSCs)gained a widespread attention,which can be ascribed to the advantages of perovskite cells such as high extinction coefficient,bipolar carrier transport properties,simple structure,and convinent to large-scale production and so on.Up to now,power conversion efficiency of PSCs has been greatly improved,making it comparable to commercial silicon-based solar cells.However,there exists disadvantages such as narrow spectral response range,many thin film surface defects,poor stability due to humidity sensitivity and low interface charge transfer efficiency that hinder the devlopment of PSCs.Therefore,it is necessary to adjust the band gap of perovskite,optimize the crystallization and morphology of perovskite,introduce hydrophobic materials,and reduce the energy loss of charge transport,so as to expand its spectral response range,reduce surface defects,improve hydrophobicity and stability,and accelerate charge transport efficiency.Brodened spectral response range of perovskite was studied by adjusting the band gap of perovskite.Introduce narrow-banded formamidinium iodide in perovskite can expand perovskite lattice,extending the spectral response to near-infrared region.When the proption of narrow band gap material is too large,the device voltage will be attenuated due to excessive lattice expansion.Thereafter,by introducing a new bromine element,it can adjust the lattice constant of perovskite under the premise of less influence on spectral absorption,thereby achieving an increase in the open circuit voltage.As a result,the spectral response of the PSCs is widened to the near-infrared region,open circuit voltage is improved,and power conversion efficiency of PSCs is also increased from 12.6%to 14.8%.Research on reducing perovskite defects was carried out by means of constructing coordination polymers modified perovskite film.A solvothermal method was used to synthesize the coordination polymer with the most common nitrogen-containing heterocyclic phenanthroline as the organic ligand and the most commonly used main group elements in semiconductors metals Indium as the metal center[In2(phen)3Cl6]CH3CN·2H2O(abbreviated as P1),and it was applied in PSC based on study the photoluminescence property and energy level characterizations of P1.Through introducing P1 into the lead iodide precursor solution to get the perovskite film via the two-step method,the crystallization and morphology of the corresponding lead iodide film was investigated.As a result,lead iodide film with reduced surface defects is obtained,the quality of corresponding perovskite film has been significantly improved.The main improvement is the expansion of particile size,the reduction of grain boundary defects,the increase of film coverage,and the close connection between particles,thus reducing the surface defects.After that,the fluorescence emission and lifetime decay test illustrated the modified perovskite film has better optical properties and longer carrier lifetime.The corresponding power conversion efficiency shows a significant improvement up to 17.15%.Research on improving the stability of PSCs was conducted through energy level matching engineering.Due to mismatch on energy level between perovskite and the hole transport layer,tetra-tert-butylpyri dine(TBP)and lithium bis-trifluoromethanesulfonimide(LI-TFSI)in the hole transport layer material is prone to deliquescence in the air,thereby reducing the long-term stability of PSCs.Considering that energy level of P1 mathes with the hole transport layer,and coordination polymer has good hydrophobicity,therefore,P1 was introduced into the hole transport layer through energy level matching engineering,which effectively reduces the energy level mismatch,accelerates the charge transport,suppresses charge recombination between the interface of perovskite and hole transporting layer,increases the power conversion efficiency,reduces the hystersis and improves long-term stability of PSCs.Study on improve the interface charge transport efficiency by improving the conductivity of the hole-transporting material was investigated.Due to the low intrinsic conductivity and hole mobility of the hole transport layer Spiro-OMeTAD,the PSCs need to be stored in dry air condition to oxidize 2,2',7,7'-Tetrakis(diphenylamino)-9,9'-spirobifluorene(abbreviated as Spiro-OMeTAD)for one night,this will inevitably hinder the stability of PSCs.Therefore,a more hydrophobic coordination polymer[In0.5K(3-qlc)Cl1.5(H2O)0.5]2n(abbreviated as P2)with oxidizing group 3-quinolinecarboxylic acid as the ligand and element indium as the central metal,and a coordination polymer{H[Zn3(OH)(TPO)2]·3DMF·2H2O}n(abbreviated as P3)with environmentally friendly and cost-effective elemental Znic as the metal center were selected and directly modified into the Spiro-OMeTAD solution,respectively.The results show that P2 and P3 can enhance the oxidation driving force of Spiro-OMeTAD,achieving directly oxidation of Spiro-OMeTAD to Spiro-OMeTAD+.The oxidized Spiro-OMeTAD+can speed up charge separation and charge transport,without the need for air oxidation,PSCs can maintain high photoelectric conversion efficiency with shortened fabrication process.