Perovskite/Organic Integrated Solar Cells

Owing to the excellent optoelectronic properties of perovskite materials,as well as the continuous optimization of the device structure and fabrication technology ofperovskite solar cells(PSCs),the PSCs have achieved rapid development in recent years.At present,the power conversion efficiency(PCE)of PSCs has approached or surpassed some commercialized solar cells.To further improve the efficiency of the perovskite solar cell,improving the absorption and utilization of near-infrared light is an effective method.Therefore,in this thesis,the perovskite/organic integrated solar cells are prepared to enhance the utilization of near-infrared light by integrating a low band gap organic active layer on the perovskite active layer,thereby improving the performance of the device.The main work of this thesis on the research of perovskite/organic solar cells includes:firstly,the perovskite film is optimized,and then the research on the integrated solar cells is carried out based on the high-quality perovskite film.The specific research content includes the following four parts:1)High-quality CH3NH3PbI3 film is prepared by a simplified close-space sublimation(CSS)method.In this method,a highly crystalline,uniform and dense perovskite film can obtain by controlling the reaction time of the PbI2 and CH3NH3I,the thickness of the PbI2 and CH3NH3I layers and the distance of the sublimation space.The preparation process of CSS method is simple and controllable.The preparation process is optimized by studying the photovoltaic performance of planar heterojunction PSCs based on CH3NH3PbI3 films fabricated by CSS method with different annealing times,different perovskite thicknesses and different photoactive area.Finally,the optimized PCE of the PSCs with an active area of 4mm2 can reach 16.2%,and the optimized PCE of the PSCs with an active area of 100 mm2 can also reach 11.4%.The results reveal that the simplified CSS method can be used to fabricate large-dimensional PSCs,which provides a new choice for the fabrication of perovskite films in the future.2)Introducing carbon quantum dots(CQDs)as additive to passivate the grain boundary of CH3NH3Pbl3 and to prepare highly efficient and stable PSCs.The appropriate concentration of CQDs adds to the CH3NH3PbI3 film can effectively passivate the grain boundary,reduce the trap-state density,and improve the photophysical properties of CH3NH3PbI3 film.In addition,the introduction of CQDs additives can greatly improve the stability of the CH3NH3Pbl3 film.The passivation of the grain boundary is attributed to the carboxyl group,hydroxyl group and amino group at the edge of the CQDs bonding with the uncoordinated Pb ions in the perovskite crystal.Because of the interaction between the CQDs and CH3NH3PbI3,the CQDs can adsorb on the surface of CH3NH3PbI3 to form a block layer,which can prevent the contact of the perovskite and water,thereby improving the stability of the PSCs.Finally,the PSCs based on the CQDs added CH3NH3PbI3 film achieves higher PCE and better stability and its' highest PCE reaching 19.38%.3)The integrated solar cells(ISCs)with CH3NH3PbI3/PBDTTT-E-T:IEICO bi0 active layer is prepared.The low band gap active layer(PBDTTT-E-T:IEICO)is deposited on perovskite layer to broaden the absorption spectrum and improve the absorption and utilization of near-infrared light for PSCs.In ISCs,both CH3NH3PI3I3 and PBDTTT-E-T:IEICO can absorb photons and generate charges.At the same time,the charges generated in the two active layers can be transferred between the two layers.Owing to the current contribution of PBDTTT-E-T:IEICO active layer,the photoresponse of ISCs is extended to 930 nm and the short-circuit current density(Jsc)is increased to 24.07mA/cm2.Moreover,the ISCs obtains an EQE of over 50%in the near-infrared region(800-830 nm).Therefore,the output current of the CH3NH3PbI3/PBDTTT-E-T:IEICO ISCs is much higher than that of the PSCs based on single CH3NH3PbI3 active layer.The results demonstrate that the perovskite/organic integrated structure can effectively expand and enhance the near-infrared light absorption and employment for PSCs4)All-inorganic perovskite/organic ISCs is studied using CsPbI2Br and PBDTTT-E-T:IEICO active layers.First,the CsPbI2Br film is prepared via vacuum solvent treatment method.By optimizing the time of vacuum solvent treatment,a highly crystalline,uniform and dense CsPbI2Br film is obtained.Then,the CsPbI2Br/PBDTTT-E-T:IEICO ISCs is studied.According to fluorescence and transient absorption tests,there is effective charge transfer in CsPbI2Br and PBDTTT-E-T:IEICO and the transportation of charge between CsPbI2Br,PBDTTT-E-T and IEICO are analyzed.The all-inorganic pero vskite/organic ISCs based on CsPbI2Br/PBDTTT-ET:IEICO achieves a PCE of 14.03%,which is 11.97%higher than that of the traditional all-inorganic PSCs(12.53%).In addition,the CsPbI2Br/PBDTTT-E-T:IEICO ISCs also exhibit better air stability and thermal stability.