Preparation And Research Of Fibrous Perovskite Solar Cells Based On Inorganic Electron Transport Materials

Perovskite solar cells（PSCs）have received widespread attention due to the rapid improvement of photoelectric conversion efficiency（PCE）.Due to its advantages of high efficiency,light weight,and simple preparation process,the application ofPSCs has gradually extended to the field of wearable devices.High efficiency PSCs often use rigid glass as the substrate,and ITO or FTO thin films as electrodes.These rigid glass electrodes have many drawbacks,such as heavy weight and easy breakage,making it difficult to meet the application requirements of wearable devices well.Therefore,this article attempts to assemble fibrous perovskite solar cells（fPSCs）based on the selection of substrate materials,using Ti wires with good flexibility and conductivity as the substrate.During the assembly process of the device,we selected different inorganic electron transport materials and studied the impact of the differences in electron transport layers on the device performance.At the same time,this article introduces a vapor assisted deposition method in the film-forming process of fPSCs,which improves the surface morphology of fibrous perovskite films and thus improves the performance of the device.The main research content is as follows:（1）In the optimization of the electron transport layer,we selected two materials,titanium dioxide（TiO₂）and tin dioxide（SnO₂）,inorganic electron transport materials,as research objects.Firstly,nanorod-type TiO₂ electron transport layer and dense TiO₂electron transport layer were prepared by hydrothermal method and sol-gel method,respectively.During the preparation process,the morphology of the nanorod like electron transport layer is controlled by adjusting parameters such as hydrothermal temperature and hydrothermal time.The experimental results show that the TiO₂ morphology obtained under hydrothermal temperature and time control of 180℃and 90 minutes is the best,and the performance of the assembled fPSCs device reaches 2.46%.Compared with hydrothermal method,the devices prepared by solution gel method achieved 2.07%PCE.We also compared SnO₂ based devices prepared with different concentrations of SnO₂solution,and the results showed that the device performance was the best when the concentration of SnO₂ precursor was 1.36 wt%,achieving a PCE of 2.45%.（2）A TiO₂/SnO₂ double electron transport layer was prepared and a fPSCs was assembled on this basis.The single electron transport layer will have some shortcomings,such as insufficient electron mobility and instability under light.Therefore,this chapter experiments attempt to superimpose TiO₂ and SnO₂ materials to prepare the two-electron transport layer to improve the performance of the device.By regulating the concentration of SnO₂ precursor solution,different thicknesses of SnO₂ layers were covered on the nanorod shaped TiO₂ electron transport layer formed by hydrothermal method,ultimately forming a composite electron transport layer.Through tests such as XPS and EDS,we confirmed the presence of Ti and Sn elements on the surface of the titanium wire and observed their uniform distribution.The experimental results show that the existence of SnO₂ can smooth the surface of nanorod TiO₂ and play a good support role for the growth of perovskite crystals.Through SEM testing,we found that perovskite thin films grown based on composite electron transport layers have smoother surfaces and larger crystalline particles.Finally,the PCE of the device based on the TiO₂/SnO₂ dual electron transport layer reached 3.81%.（3）On the basis of TiO₂/SnO₂ dual electron transport layer,we prepared perovskite thin films by gas-assisted deposition of CH₃NH₃I（MAI）and lead iodide（PbI₂）thin films,and studied the effect of evaporation time on the morphology of perovskite thin films.The experimental results have shown that compared to the solution coating method,the vapor assisted deposition method can obtain a more uniform and flat perovskite film,and the improvement effect is best when the device reacts in MAI vapor for 3 hours.The final device has a PCE of 5.35%and a lower hysteresis coefficient.By conducting PCE statistics on the assembled PSCs,it was found that the PCE of 20 devices assembled using vapor assisted deposition method is higher and has smaller dispersion,resulting in higher stability performance.