P-type Materials Applied In Inverted Perovskite Solar Cells

Organic-inorganic hybrid perovskite solar cells?PSCs?have attracted a great deal of attention owing to their high absorption coefficient and ambipolar charge transport properties as well as flat,highly uniform thin films.For PSCs,the power conversion efficiency?PCE?has increased from initial 3.8%to newly 22.7%in the last few years.However,the problems of stability and cost of PSCs have not been solved,which will retard the commercial development of the PSCs.Thus,the inverted p-i-n PSCs in which the perovskite films are deposited onto the hole transporting layer,have received great attention for their simple device fabrication,low hysteresis and low temperature process.In this thesis,my topic is focused on the application of P-type semiconductor in inverted PSCs?i-PSCs?with three representative hole transporting materials?HTMs?,involving poly?3,4-ethylenedioxythiophene?polystyrene sulfonate?PEDOT:PSS?,nickeloxide?NiO_x?and4,4?,4??-tris?N-3-methylphenyl-N-phenylamino?triphenylamine?m-MTDATA?.Also,UV-Vis spectrophotometer?UV-Vis-NIR?,scanning electron microscope?SEM?,atomic force microscope?AFM?,X ray diffraction analysis?XRD?,conductivity test,mobility test,electrochemical workstation?EIS?,J-V curves have been used to illustrate the effect of P-type semiconductors in PSCs.Aiming to optimize the PCE,reduce the cost and improve the stability of cells,the main contents of this thesis are listed as following:1.Based on the optimized volume ratio value at 1:3 of PEDOT:PSS and methanol,we used the environmentally friendly green solvent ethyl acetate as anti-solvent to control the crystallization of perovskite films.It was found that adding Cs and Formamidine?FA?to CH₃NH₃PbI₃?MAPbI₃?in PEDOT:PSS-based i-PSCs leaded to the higher efficiency and stability.2.We chose the spray pyrolysis method to fabricate NiO_x films and the thickness of NiOx films was set up to 20 nm.Then we introduced a fullerene pyrrolidine derivative of N-methyl-2-pentyl-[60]fullerene pyrrolidine?NMPFP?synthesized via Prato reaction of C₆₀ directly with cheap hexanal and sarcosine.The one-step reaction made the use of the shelf chemicals and did not require an inert atmosphere or highly purified or anhydrous-grade solvents,which resulted in one-fourth of the manufacturing cost compared to[6,6]-phenyl-C₆₁-butyric acid methyl ester PCBM in a lab scale such as 1 g.The new fullerene derivative NMPFP as an alternative low-cost electron transporting layer?ETL?to PCBM was employed in the i-PSCs.Compared with the PCBM-based cells,the devices with the NMPFP ETL yield a comparable efficiency.3.We introduced a novel organic small molecule m-MTDATA to replace PEDOT:PSS as hole transporting layer?HTL?in the i-PSCs without any dopants.The price of m-MTDATA is lower than Poly[bis?4-phenyl??2,4,6-trimethylphenyl?amine]?PTAA?.The dopant-free m-MTDATA-based device showed significantly improved performance with a PCE of 18.12%.This performance is superior to that of the standard PEDOT:PSS-based PSC?PCE=13.44%?.Also,the PCE showed negligible dependence on the thickness of the m-MTDATA film.In addition to its high device performance,it also showed a long-term stability over 1000 h in room temperature with only a small of the initial performance decreased and a good illumination stability during 80 h.