Growth And Research Of CH₃NH₃PbI₃/p-Si Heterojunction

Organic-inorganic hybrid perovskite solar cells have become one of the hot spots in recent years because of the advantages like low cost and high efficiency.However,problems like thermal instability of organic hole-transporting materials become the bottleneck for further development of PSCs.In this paper,a p-type silicon is used to replace the traditional organic hole-transport material to transport holes to improve the stability of solar cells.The CH₃NH₃PbI₃ film is prepared on p-type silicon substrate to form CH3NH3PbI3/p-Si heterojunction.The characteristics of the CH₃NH₃PbI₃/p-Si heterojunction are studied,which can be used as a reference for fabricating perovskite/p-Si heterojunction solar cells with high efficiency and long-term stability in the future.The main research contents and results are as follows:1.CH₃NH₃PbI₃ thin films are prepared by using one-step solution method and sequential deposition method,respectively.The influence of substrate temperature,spin rate,annealing temperature,CH₃NH₃I concentration and dipping time on the morphology and electrical properties of the film is studied by AFM,SEM,XRD and I-V test,respectively.It turns out that the surface morphology and crystallization of the CH₃NH₃PbI₃films was improved significantly when the substrate temperature is 40°C,spin-coating speed is 3000rpm and annealing temperature is 100°C in one-step solution method.And CH₃NH₃PbI₃ films prepared by sequential deposition method have PbI₂ crystal residues.This might be caused by the incomplete reaction of PbI₂ with CH₃NH₃I solution,because in planner structure the PbI₂ grain size might become very large without the limitation of mesoporous structure.2.I-V curves with and without illumination show that CH₃NH₃PbI₃/p-Si heterojunction have rectifier features and photoelectric conversion features with short circuit current(I_sc)of 0.16uA and open circuit voltage(V_oc)about 10mV.C-V test of CH₃NH₃PbI₃ film shows a non-linear dielectric property and the dielectric value is about4.64 as calculated.The high frequency C-V characteristic of Ag/CH₃NH₃PbI₃/p-Si heterojunction turns out to be similar with that of Metal-Insulator-Semiconductor?MIS?structure,and a parallel translation of the C-V curve along the forward voltage axis is found.This parallel translation means the existence of defects at CH₃NH₃PbI₃/p-Si interface and positive fixed charges in CH3NH3PbI3 layer.The defects at the interface of CH3NH3PbI3/p-Si heterojunction result in the dramatic decline of the Voc.