Synthesis Of Novel Organic Hole Transport Materials And Their Applications In Organic/perovskite Solar Cells

At present,perovskite solar cells（PSCs）have been developed rapidly,and their power conversion efficiency has reached a record high（PCE）and exceeded 25%within ten years.Hole transport materials（HTMs）play an important role as a part of perovskite solar cells.A bottleneck in the commercialization of PSCs is the lack of stability due to the commonly used dopants of hole transport materials.These hygroscopic dopants not only deteriorate the stability for a long time due to the entry of moisture and the diffusion of ions,but also increase complexity and total cost.Therefore,the development of undoped HTMs is of great significance.In order to make the current undoped HTMs closer to the ideal HTMs,a series of novel organic undoped hole-transport materials were designed and synthesized in this paper,and the synthesized intermediates and target molecules were characterized by ¹H NMR/¹³C NMR spectroscopy and other detection methods.At the same time,it also uses density functional theory（DFT）calculations,DSC and TGA thermal analysis,ultraviolet-visible absorption spectroscopy（UV-Vis）,cyclic voltammetry（CV）,atomic force microscope（AFM）,contact angle tester,scanning electron microscope（SEM）characterized the photophysical,electrochemical properties and morphology of the hole transport layer and perovskite layer,and the preparation of the PSCs based on the HTMs to determine its photovoltaic properties,and systematically studies the relationship between structure and performance of materials,to improve the performance of perovskite solar cells.To provide design strategies for future commercial applications.The specific research results are as follows:1.This chapter synthesized a new type of SPBD core with intermediate interruption of the conjugate through the cheap industrial product bisphenol A,and then used methoxydiphenylamine and methyldiphenylamine as donor units through a simple Buchwald–Hartwig coupling reaction to obtain low-cost molecules TMe OPSIDA and TMe PSIDA.The photophysical properties,thermodynamic properties,film morphology,hole mobility and device performance of the two materials were studied.Because methyl group is less electronegative than methoxy group,using methyl diphenylamine as the end group can obtain a lower HOMO level and improve the molecular hole mobility.The designed HTMs and the mixed ion perovskite FA _0.85 MA_0.15Pb(I_0.85 Br_0.15)₃ were used to prepare the devices.Under standard illumination(AM 1.5G and 100 m W cm^-2),the average PCE of TMe OPSIDA and TMe PSIDA devices were 15.75%and 17.30%,respectively,and the short-circuit current density(J_sc)were 20.30 m A cm^-2 and 20.52 m A cm^-2,respectively.The open circuit voltages(V_oc)are 1.05 V and 1.08 V,and the filling factors（FF）are 73.87%and 78.06%,respectively,showing good device stability.Due to the advantages of high performance and high stability,the newly developed HTMs are expected to be candidate products for low-cost perovskite solar cell devices.2.This chapter chose the symmetrically substituted fluorene derivative spiro[fluorene-9,2’-[1,3]dithiolane]（SPFDS）containing a spiro dithiolane ring at the C-9 position.SPFDS is a commonly used semiconductor molecule of fluorene derivatives.Its rigid planar structure is conducive toπ-πinteraction between molecules.At the same time,the sulfur atoms of the dithiopentyl unit in the SPFDS structure can passivate the defects more effectively by coordinating the Pb²⁺vacancy in the perovskite.SPFDS was used as the acceptor unit to construct D-A type hole transport materials,the target material is synthesized by Suzuki-Miyaura and Buchwald-Hartwing coupling reaction,and four novel HTMs,SPFDS1,SPFDS2,SPFDS3 and SPFDS4,with methyl diphenylamine,methyl triphenylamine thio-methyl diphenylamine and thio-methyl triphenylamine as terminal groups,were constructed using SPFDS as the nucleus.At the same time,the undoped indium tin oxide（ITO）/HTM/perovskite/C60/BCP/Cu inverted PSC devices with SPFDS1,SPFDS2,SPFDS3,SPFDS4 and PEDOT:PSS as HTMS were fabricated.Therefore,in inverted-PSCs,the efficiency of dopant-free HTMs SPFDS1,SPFDS2,SPFDS3 and SPFDS4,is 18.94%,19.41%,20.02%and 18.20%respectively,all of which are higher than that of PEDOT:PSS 15.04%.At the same time,under inert conditions,the PSCs based on four HTMs maintained an initial efficiency of 80%for nearly 1000 hours,which is much more stable than the 30%efficiency when using PEDOT:PSS as HTMs,showing better device stability.3.Two novel HTMs based on alkyl bromide substituted carbazole（Br Cz）core with methyl diphenylamine and methyl triphenylamine as terminal groups are reported.The use of methyl,rather than methoxy,for diphenylamine and triphenylamine is conducive to the reduction of the highest occupied molecular orbital（HOMO）level of HTMs,which leads to a higher open circuit voltage(V_oc).Using industrial raw materials as raw materials,two HTMs were synthesized in two simple steps.At the same time,Br Cz-Me TPA,Br Cz-Me DPA or PEDOT:PSS as HTMs doped indium tin oxide（ITO）/HTM/perovskite/C60/BCP/Cu PSC devices were prepared.Therefore,in inverted PSCs,as dopant-free HTMs,the efficiency of Br Cz-Me TPA was 19.14%and the efficiency of Br Cz-Me DPA was 20.61%,both exceeding that of PEDOT:PSS（17.46%）.At the same time,under inertial conditions,PSCs based on Br Cz-Me TPA and Br Cz-Me DPA maintained an initial efficiency of 78%for nearly 1000 hours,which was much more stable than the 30%efficiency when PEDOT:PSS was used as HTM.4.A D-A conjugated polymer P（Th TIc-BDT）was synthesized from fused ring lactone and benzo[1,2-b:4,5-b’]dithiophene（BDT）unit.Polymer is used as donor material in BHJ.Polymer:A1 active layer is integrated with perovskite to prepare BHJ/perovskite integrated solar cells.The absorption spectrum of the device is broadened by integrating a narrow band gap BHJ active layer on the perovskite layer.Meanwhile,ITO/Sn O₂/perovskite/P（Th TIc-BDT）:A1/Mo O₃/Au were fabricated.Due to the the narrow band gap polymer:A1 current contribution,the optical response of the cell device was widened to 950nm,achieving an efficiency of 22.6%,and the short-circuit current density was increased to 25.75 m A/cm².Meanwhile,the unencapsulated cell was aged in air（relative humidity<30%）for 60 days.The PCE of the Sprio-OMe TAD-based perovskite solar cell and the integrated solar cell attenuates to 54.8%and 93.4%of the initial PCE,respectively.After being heated to 85℃in a nitrogen filled glove box for 200 hours,the PCE efficiency of the Sprio-OMe TAD-based perovskite solar cell decreased to 0 after 120 hours,while the integrated solar cell efficiency maintained to 81.1%of the initial PCE.5.Porphyrin-based small molecules and polymers materials SMP1,SMP2,SMP3,PL1,PL2were designed and synthesized.First,we study the porphyrin base of small molecules and polymers in the performance of organic solar cells,the preparation of glass/ITO/PEDOT:PSS/active/Zn O/PNF-Br/Al structure of BHJ OPV device,the five molecules as donor materials got the PCE of 5.32%,3.14%,8.59%,5.73%,7.14%,respectively.SMP3 has the highest power conversion efficiency.Meanwhile,a normal device with ITO/Sn O2/perovskite/porphyrins/Au structures using porphyrin-based small molecules and polymers as HTMs was prepared.The PCE of PSCs based on SMP1 was 17.78%,J_sc 19.69 m A cm^-2,V_oc1.10 V,and filling factor（FF）80.99%,while the PCE of PSCs based on SMP2 was slightly lower(PCE was15.36%,corresponding J_sc 19.01 m A cm^-2,V_oc was 1.06V and FF was 78.70%).SMP3 based PSC achieved the highest PCE of 18.52%,corresponding to a J_sc value of 21.32m A cm^-2,V_oc of 1.09 V,and FF of 79.77%.The PCE of PL1 PSCs was 15.42%,J_sc was 18.49m A cm^-2,V_oc was 1.05 V and FF was 79.32%.The PCE of PL2 PSC was slightly higher than that of PL1（16.78%）,corresponding to the J_sc value of 19.93m A cm^-2,V_oc value of 1.08 V,FF value of 78.28%.This paper aims to obtain high-efficiency perovskite solar cells,designs and synthesizes high-efficiency dopant-free low-cost hole transport materials,and in-depth study of the photoelectrochemical and physical properties of hole transport layer materials.The interface and hole transport properties were characterized,and the device realized a highly efficient and stable perovskite solar cell,which provided useful ideas and practices for the further development of perovskite solar cells.