Preparation Of CoO Nanoplates And Co²⁺doped CuGaO₂ Nanocrystallines And Their Applications In Perovskite Solar Cells

Perovskite solar cells?PSCs?have attracted wide attention due to their excellent optical properties and simple device fabrication processes.Since first reported in 2009,the photoelectric conversion efficiency?PCE?of PSCs has soared from 3.8% to 25.2%.However,the perovskite polycrystalline film is easy to decompose and the organic hole transport materials?Spiro-OMeTAD,etc.?are expensive,which limits the commercial application of PSCs.Therefore,improving the stability of perovskite films and searching for cheap and efficient inorganic hole transport materials have become the current research hotspots.In this paper,two kinds of inorganic p-type nano-materials CoO and Co²⁺doped CuGaO₂?Co-CuGaO₂?are innovatively synthesized for the purpose of improving the photoelectric performance and long-term stability of PSCs.They are used as perovskite surface interface modification materials and hole transport materials?HTM?for PSCs and for the preparation of organic-inorganic double hole transport layers?HTL?.Tin-doped indium oxide?ITO?conductive glasses with low surface roughness are used as the conductive substrate,and titanium dioxide?TiO₂?nanoparticles after stripping organic ligands are used as the electron transport material?ETM?.The main research contents and results are as follows:?1?Inorganic p-type CoO nanoplates are synthesized by the solvothermal method,which are dissolved in toluene to prepare a uniform solution,and spin-coated on the surface of the perovskite layer to improve the performance and stability of PSCs.TEM,XRD,and XPS tests are used to characterize the morphology and composition of CoO nanoplates,and the results show that CoO has a plate-like structure around 10 nm;SEM,AFM,UPS,PL,TRPL tests show that the CoO interface modification layer can effectively passivate the surface defects of the perovskite,improve the moisture resistance of the perovskite polycrystalline film,optimize the energy level structure of the device,and improve the carrier transport performance.By optimizing the concentration of the CoO solution,the reverse scanning PCE of the PSCs device is up to 20.72%,and after 30 days in an air atmosphere with 30% to 50% relative humidity,the original efficiency can remain 82.61%.?2?Spiro-OMeTAD/CoO composite HTL is prepared by introducing inorganic p-type CoO nanomaterials as HTM into the HTL of PSCs.The purpose is to combine the advantages of Spiro-OMeTAD and CoO through an organic-inorganic method to prepare high-efficiency PSCs with good stability and high hole transport efficiency.We observe the morphology of the composite HTL and the dispersion state of CoO through SEM,FIB-SEM,and AFM;The hydrophobicity of the surface of the composite HTL is verified by contact angle test.The test methods such as PL,TRPL,EIS,and n_trapare used to verify that Spiro-OMeTAD/CoO composite HTL can reduce internal defect states of perovskite and improve hole transport performance.By optimizing the CoO concentration,PSCs achieve a high efficiency of 20.91%,and maintain the original efficiency of 82.58% after 400 h stability test under 40% to 55% relative humidity.The results show that inorganic p-type CoO nanomaterials play an important role in improving the performance and stability of PSCs.?3?Co-CuGaO₂ nanocrystals with a particle size in the range of 15²5 nm are prepared by the hydrothermal method,and then used as inorganic HTLs for PSCs.Co²⁺doping can reduce the position of valence band of CuGaO₂ and make the energy levels of Co-CuGaO₂ film and perovskite more closely match;In addition,CuGaO₂ itself has a wide band gap,which is conducive to transporting holes and blocking electrons.SEM tests show that the Co-CuGaO₂ film completely covers the underlying perovskite,which is beneficial to protect the perovskite crystals from damage by water and oxygen.Moreover,Co-CuGaO₂ itself,as an excellent HTM,can form an organic-inorganic double HTL structure with the Spiro-OMeTAD layer,further improving hole transport performance.This has been verified by tests such as UPS,PL,TRPL,etc.By optimizing the concentration of the Co-CuGaO₂ solution,the maximum PCE of the PSCs was 20.39%;and maintained the original efficiency of 84.34% after 30-days stability test under 10±5% relative humidity.