Performance Improvement Of The Planar Heterojunction Perovskite Solar Cells By Interface Modification

As an ideal absorber with excellent properties,organic-inorganic perovskite was regarded as the most promising materials for the next generation of solar cells.The planar structure device attracted lots of attention because of its simple structure,potential application in flexible devices.However,the defects in the surface and grain boundary of the perovskite layer may result in charge recombination at the interface of the perovskite layer.Besides,the energy level between the electron transport layer and the perovskite layer also determines the ability to extract electrons and block holes,thus affecting the device performance.Therefore,it is a simple and effective method to select high electron mobility,high conductivity,high stability of the electron transport material,and to improve the interface properties between the perovskite,electron transport layer and the electrode.In this thesis,research work concerns the interfacial modification of electron transport layer was conducted as follows:1.The interface of the electron transport layer PCBM was modified by adding Polyvinylcarbazole(PVK)and 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone)-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']-dithiophe ne(ITIC).The addition of PVK and ITIC can improve the film-forming properties of PCBM,which forms a good interface contact and reduces the interface defects.Besides,the device charge separation efficiency was effectively improved and the charge recombination was inhibited.The optimal device was obtained when the PVK content is 4wt% and the ITIC content is 6wt%.Compared with the control device without additives,the power conversion efficiency(PCE)was increased from 5.26% to 9.93%,with Voc = 0.95 V,Jsc = 15.97 mA /cm2 and FF = 65.42%.In addition,the addition of PVK and ITIC inhibits the moisture and oxygen in the atmosphere into the device and improve the stability of the device.2.The interface of the PCBM/Al was modified by N,N'-di-n-octyl-3,4,9,10-perylene tetracarboxylic diimide(PTCDI-C8).Since PTCDI-C8 have high electron mobility and a smoother film can be formed on the PCBM surface,the leakage current between the PCBM and the Al electrode was reduced,thereby improving the electron collection efficiency of the cathode.In addition,the presence of the PTCDI-C8 layer can block the movement of holes toward the electrode and reduce the charge recombination at the interface.The optimal device was obtained for PTCDI-C8 film is 20 nm.Compared with the control device without the PTCDI-C8 layer,the PCE was increased from 5.26% to 8.65%,with Voc = 0.92 V,Jsc = 15.68 mA/cm2 and FF = 60%.In addition,the stability of the device was improved because of the high stability and barrier ability of PTCDI-C8.