Preparation And Interface Modification Of High Performance Perovskite Solar Cells

Organic-inorganic hybrid perovskite solar cells?PSCs?developed very fast recently.With the advantages of high conversion efficiency,low cost,low energy imput and solution-fabrication process,this kind of solar cell attracted great attention.The core materials,including the electron transport layer,the perovskite light absorption layer,and the hole transport layer,play a crucial role for fabricating novel performance perovskite solar cells.Interfacial structures and behaviors also have a major impact on performance of PSCs.In this thesis,effects of electronic transport layer?ETL?and perovskite absorbable materials on photovoltaic performance of PSCs were investigated,and the mechanism was studied by several characterization methods.The effects of interface modification between them on the photovoltaic performance of the perovskite cells were researched carefully.The main results are summarized as follows:?1?A method combined Solvent-annealing and Direct contact and Intercalation Process?DCIP?was applied to prepare perovskite absorption layer with uniform crystallization and large crystal grains.The result indicated that the average particle size of perovskite increased from about 300 nm to over 1200 nm when the addition amount of DMSO was 15?l in a 500 ml chamber,and the PCE of the corresponding cell was also increased from 11%to 14.33%.This method provided a promising direction in promoting the performance of the PSCs and fabricating large area PSCs.?2?A compact TiO₂ film employed as an electron-transport layer?ETL?was modified using 3-aminopropyl trimethoxy silane?APMS?hydrolysate.The power conversion efficiency?PCE?of PSCs composed of an APMS-hydrolysate-modified TiO₂ layer increased from 13.45%to 15.79%,which was associated with a significant enhancement in the fill factor?FF?from 62.23%to 68.04%.The results indicated that APMS hydrolysate enhanced the wettability of?-butyrolactone?GBL?on the TiO₂ surface,resulting the formation of a perfect CH₃NH₃PbI₃ film.The PL spectra showed after the modification of APMS hydrolysate,photoelectron injection into the electron transport layer was promoted,leading to a result of enhanced J_sc.C-V test indicated that the surface traps of TiO₂ could be passivated by the APMS hydrolysate,improving the FF of the devices.EIS tests revealed that the recombination resistance of the TiO₂/perovskite interface increased as wel which was beneficial to the photovoltaic performance.?3?A new perovskite growth method was presented here using the Methylammonium Chloride?MACl?to assist the vertical recrystallization in FA_xMA_1-xPbI_yBr_3-yfilm.The performace of the devices were enhanced by introducing the MACl.The materials were characterized by means of several techniques to investigate the intrinsic reason for the improvement of photovoltaic performance.The power conversion efficiency?PCE?of the best device fabricated by the obtained film was 18.55%.The PCE of the device was proportional to mass concentration of MACl doping in perovskite.SEM results showed that the grain size of perovskite film increased with the increasing of the mass concentration of MACl dopant in perovskite.The cross-sectional SEM demonstrated that when doped with 50%MACl,the perovskite film only had a vertical grain boundary.When the photoelectron passes through the one-direction decreased grain boundary,less energy loss and a significant increase in the short-circuit current could be obtained.The XRD patterns showed that the yellow?phase of perovskite disappeared after doping MACl,and on the other hand the black?phase increased.UV absorption characterization suggested that with rise of the amount of the black?phase an increase in visible light absorption was obtained.The PL spectra showed a promotional photoelectron injection into the electron transport layer with the increasing mass concentration of MACl doping in perovskite.The IPCE of the device was positively dependent on the doping amount of MACl in perovskite as well.?4?We studied the parameters that could influence the photovoltaic performance in PSCs using spin-coated TiO₂,Sn O₂,and bilayered electron transport layers?ETL?of SnO₂/TiO₂ and TiO₂/SnO₂,which were annealed at150°C.The optimum best PSC,which was fabricated as a combination structure of ITO/TiO₂/SnO₂/perovskite/HTM/Au,exhibited a PCE of 20.15%with reduced hysteresis.Compared with TiO₂,SnO₂ layer brought a better bandgap matching to the perovskite/ETL interface that facilitated charge extraction and diffusion in ETL.Hence,combining the high-mobility SnO₂and efficient hole-suppression TiO₂,the TiO₂/SnO₂ composite layer worked efficaciously and achieved the optimized matching.