| Energy is one of the key problems facing human society.Solar energy as a clean energy has broad development prospects and application prospects.Solar cell is a kind of device which converts solar energy into electric energy.Organic-inorganic hybrid perovskite material has attracted extensive attention due to their large absorption coefficient,direct band gap,high carrier mobility and diffusion length.In ten years,the efficiency of PSCs has increased from 3.8% to 23.7%,and its efficiency has improved faster than other solar cells.The PSCs are generally composed of electron transfer layer(ETL),perovskite absorption layer,and hole transfer layer(HTL).The HTL is one of the indispensable factors for high efficiency of PSCs.Organic HTMs have been commonly used in high-efficiency PSCs,such as 2,2’,7,7’-tetrakis-(N,N-p-dimethoxyphenylamino)-9,9’-spirobifluorene(Spiro-OMeTAD),polytriarylamine(PTAA),Nano-fibμLar polyaniline(PANI),and other small molecμLes.However,the application of these organic HTMs can increase the cost of PSCs,because the synthesis process of these materials is complicated and high purity is obligatory for photovoltaic application,In addition,the use of the additive can reduce the stability of PSCs.CISe is a Cu-based chalcopyrite semiconductor inorganic material,which has currently utilized as a light-absorbent material in traditional quantum dot sensitized solar cells,because of its high absorption coefficient,a finely tunable direct band gap ranging,low toxicity,simple preparation method and low production cost.However,So far,it has not been reported that CISe quantum dots are applied to PSCs as inorganic HTM.Moreover,most of the synthetic CISe quantum dots use solvothermal method.The large amount of oleylamine solvent makes the sub-surface encapsμLated with organic long chains of insμLation,which reduces the conductivity of quantum dots and seriously affects the photoelectric performance of device.Therefore,in this paper,the CISe quantum dot is applied as a HTM to the PSCs,and the organic long-chain ligand on the surface of the quantum dot is replaced with a short chain.The conductivity of the quantum dots and the photoelectric performance of the PSCs are improved.Therefore,I studied the two parts:First section:First,we synthesized CISe quantum dots using a hot-injection method with a single particle size and good dispersion.Then,we fabricated perovskite solar cells with the CISe quantum dots as a HTM for the first time and a high PCE of 12.8% was achieved for PSCs with CISe quantum dots as HTL.The most important point is that compared with the commonly used organic hole transporting material Spiro-OMeTAD,the CISe quantum dot was be used as the inorganic HTM without any impurities,which not only reduces the cost,but also improves the stability of PSCs.The PCE of PSCs based on CISe quantum dots retained 78% after 5 days in the ambient environment with 30%-50% humidity without any encapsμLation.However,the PCE of PSCs with Spiro-OMeTAD decayed to 30% after 5 days,in the same environment.It shows that CISe quantum dot is a promising inorganic HTM.Second section:The long chain on the surface of the CISe quantum dot can affect hole transport.We use the bifunctional molecμLe 3-mercaptopropionic acid to exchange the organic long-chain ligands on the surface of quantum dots into a point-chain ligand,which does not affect the dispersion of quantum dots and improve the conductivity of quantum dots.We fabricated the inverted structure PSCs with point-chain ligand quantum dots.Through characterizations,it was found that the solar transmittance of the quantum dot film after ligand exchange was improved,and the absorption of solar by the perovskite light absorbing layer was increased.In addition,the injection and transport of holes was improved with the quantum dots after ligand exchange as a HTL and the recombination of carriers in the PSCs was effectively suppressed.The performance of the PSCs was improved from 7.18% to 8.59%. |
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