Research On Carbon Electrode Perovskite Solar Cells With Cuprous Thiocyanate As The Hole Transport Layer

Organic-inorganic hybrid perovskite solar cells,as an outstanding representative of novel solar cells,have attract tremendous attention due to their rapidly increased power conversion efficiency and easy fabrication process.However,the expensive organic hole transport materials and noble metal electrodes are widely used in most of the reported high-performance devices,which heavily increase the cost of devices.The inorganic material cuprous thiocyanate(CuSCN)and carbon electrodes are promising alternatives to replace the organic hole transport layer and noble metal electrodes in the existing architecture.How to prepare high-efficiency carbon electrode devices has become one of the crucial issues in this field.In this paper,we applied CuSCN to the carbon-electrode devices as the hole transport layer,optimized the preparation process of carbon electrode and employed a pre-heated substrate method with spin-coating perovskite in order to study the influence of CuSCN solution on perovskite,the interface stability of perovskite/CuSCN film and the growth process of perovskite film,so as to improve the performance of devices.Specifically,we have carried out the following work.First,we studied the impacts of the introduction of CuSCN on device performance.Devices with CuSCN as the hole transport layers were fabricated based on the high-quality perovskite films.Then it was compared to the HTL-free devices to explore the change of device performance parameters.It is found that the solvent diethyl sulfide would erode the perovskite and lead to the degradation of device performance,and the use of polydimethylsiloxane can effectively reduce this effect and protect the perovskite film.Compared to the HTL-free devices,the CuSCN film effectively enhanced the hole extraction and suppress the non-radiative recombination of the interface.In that case the performance of devices was improved.Secondly,the interface stability of perovskite/CuSCN thin films was researched in this thesis.By comparing the changes of perovskite/CuSCN films before and after the preparation of carbon electrodes,it was explored that the effects of drying temperature on the perovskite/CuSCN interface.Further studies revealed that more SCN~-ions diffuse from CuSCN film to the perovskite film when it was heated at 100°C,which changed the energy band structure of CuSCN film and caused the mismatch of energy level between perovskite,CuSCN and carbon electrode.All the bad effects led to the low performance of the devices.In order to solve the problem,a vacuum-assisted drying process was developed to accelerate the volatilization rate of the terpineol at low temperatures,effectively alleviating the adverse effects of SCN~-diffusion and increasing the device efficiency to 15.72%.Meanwhile,the devices manufactured by this way exhibited good shelf-stability,light-stability and thermostability.Moreover,the substrate pre-heated spin-coating process was developed to obtain a high-quality perovskite film and improve the light absorption of the devices.The oriented growth of perovskite film in the direction of charge transport was promoted and larger grains was obtained when the substrates was preheated.Finally,when the substrate preheating temperature is 45°C,the light absorption of the film was significantly enhanced,and the current density of the device is also significantly improved obtained a PCE of 17.99%.In addition,this method was used to prepare the large-area devices with 74 cm~2,and a high efficiency of 12.09%was also obtained.In summary,this thesis confirms the effectiveness of CuSCN and optimized the spin coating process of CuSCN by introducing the CuSCN hole transport layer into the carbon electrode devices.On this basis,the vacuum-assisted drying method of carbon electrodes reduces the adverse effects of SCN~-diffusion.Combined with the substrate preheating method,a high-quality perovskite film is prepared to enhance the light absorption of the device,and finally the efficient and stable CuSCN carbon electrode device was prepared in dry air atmosphere.