| As the energy crisis is approaching year by year,human beings have an increasingly urgent demand for secondary energy.As an inexhaustible high-quality clean energy,solar energy is a leader in the development of various secondary energy sources.Solar cells are high-efficiency electronic energy devices that directly convert solar energy into electrical energy.However,the current mature solar cell technology still has huge drawbacks.Taking the crystalline silicon cell with an absolute market share as an example,its cost is high,the payback period is long and the conversion efficiency limit is relatively low,and the future prospects are worrying.The recent emergence of perovskite solar cells,it has advantages of low cost,high conversion efficiency and simple preparation,and has become a star material in the field of solar cell research,and it has a promising future in the field of industrial and commercial applications.Hole transport materials are indispensable key materials in high-efficiency perovskite solar cells.Hole transport materials are divided into two categories:organic hole transport materials and inorganic hole transport materials,each of which has advantages and disadvantages.Generally speaking,organic hole transport materials are widely used and have high efficiency,but they are expensive and have poor stability.Inorganic hole transport materials are less studied,their efficiency is relatively low,but the cost is low and the stability is good.Exploring how to combine the advantages of the two is the main work of the author during my Ph.D.First,we selected a high-performance inorganic hole transport material cuprous iodide.This material has low cost,strong charge transport ability,good stability and good energy level matching with the perovskite active layer.It is suitable for commercial applications.Therefore,we choose this material as hole transport material and research object.However,in the actual use process,we found that good interfacial transport could not be formed between this material and the perovskite active layer,so we used the organic transport material PEDOT:PSS as the auxiliary transport layer to form cuprous iodide/PEDOT:PSS Double-layer hole transport layer structure.The perovskite solar cell based on this structure successfully achieved an energy conversion efficiency of 14.3%.At the same time,compared with the cell based on pure PEDOT:PSS hole transport,the stability has been greatly improved.Relative conversion efficiency increased from 72%to 88%.Then,we combine the inorganic hole-transporting material cuprous iodide with the organic hole-transporting material P3HT,which is an efficient organic hole-transporting material but has not been applied to inverted structure perovskite solar cells so far.Among them,because the hydrophobicity of the P3HT is too large after film formation,perovskite cannot be coated on its surface,so it cannot be used as a hole transport layer alone,so we developed a new Cu I:P3HT composite hole transport material.Thanks to the good interfacial charge transport between P3HT and perovskite films,the device with the composite hole transport layer obtained higher VOC,FF,and PCE values than the device with the Cu（I）iodide substrate alone.At the same time,we found that the device effect of the prepared Cu I:P3HT film annealed at 150°C is better than that of the device annealed at 100°C,which is due to the increase in the consistency of the molecular arrangement of P3HT.In the end,the conversion efficiency of the device we obtained was as high as 15.0%,while the conversion efficiency of the Cu I-based device alone was only 9.52%.Through impedance spectroscopy and fluorescence spectroscopy tests,we found that the reason for the increase in the conversion efficiency of the device came from the introduction of P3HT,which led to the decrease of the interface resistance of the device and reduction of interfacial charge recombination.Finally,we set our sights on two-dimensional Mo S2,an inorganic two-dimensional material.Mo S2 is an emerging two-dimensional hole-conducting material with the advantages of low cost and good stability.However,Mo S2 itself has a large band gap and poor film formation,and we found that it could not be used as a hole transport layer alone,so we developed a PTAA/Mo S2 double-layer hole transport layer structure.Benefiting from the suitable bandgap and strong electron blocking ability of Mo S2,the devices with the double-layer hole transport layer structure obtained higher VOC,JSCand PCE values than the devices on the single PTAA substrate.At the same time,we also prepared a two-dimensional perovskite solar cell with the same structure based on two-dimensional perovskite,and found that the PCE of the device was also improved.Finally,we obtained 3D and 2D perovskite solar cells with conversion efficiencies of18.47%and 13.19%,while the corresponding device PCEs on the PTAA substrate alone were only 14.48%and 10.13%.Meanwhile,our fluorescence tests show that the 2D perovskite-based solar cells have a self-quenching effect due to the inhomogeneous phase distribution of the 2D perovskite films,and the direction of the automatic charge transfer is the same as the direction of the charge transfer when the cell is working,indicating that It is more advantageous in the inverted structure.Secondly,the perovskite solar cell based on the PTAA/Mo S2 double-layer structure is also more stable,and the relative conversion efficiency is increased from 47%to 66%after being stored in the air for 500 hours. |
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