| Intrinsic toxicity and instability are the two most considerable issues concern in lead-based Hybrid Organic-Inorganic Perovskite Solar Cells(PSCs)for commercial application.Hence,methylammonium iododibismuthate(CH3NH3)3Bi2l9(MBI)has received more attention for its low-toxicity and long-term stability.Pure MBI was synthesized by solution and vapor processing,respectively,and was systematically studied the crystal structure,stability and photoelectric properties by Hoye et al,which has greatly promoted the development of MBI film as a light-absorption layer in the PSCs.However,many hexagonal nanocrystalline flakes of MBI on the surface of TiO2 and disorderly stacked together,resulting in uncontinuous film.Besides,large area defects caused short circuit or even open circuit seriously in the device.Therefore,it is urgent to obtain high-quality,uniform and continuous films to improve the efficiency of Bi-based PSCs through interface engineering such as morphological control,some attemptions focusing mainly on the following work:(1)Rutile TiO2 nanorod array(NRA)was prepared by hydrothermal method at different reaction time on the TiO2 compact layer,then MBI films were fabricated through a two-step sequential solution process on the rutile TiO2 NRA films,follow by spinning-coated the hole transmission layer and vacuum evaporation deposited gold counter electrode to obtain the devices.X-ray diffraction(XRD)showed the(101)and(002)planes of the rutile TiO2 phase.The length of TiO2 NRA increased from 472 nm to 1073 nm with the reaction time by Field emission scanning electron microscopy(SEM).Furtherly,XRD patterns showed that MBI was synthesized by the two-step sequential solution process.UV-Vis showed that the light absorption of MBI film was related to the length of rutile TiO2,and the indirect band gap of MBI was calculated to be 2.2 eV.SEM demonstrated that the as-made MBI was hexagonal flake,the film was not dense,so that some area of bare mesoporous layer can be seen.XPS further proves that we have synthesized MBI successfully.At the same time,the J-V curve shows that the power conversion efficiency(PCE)is 0.14%with the 564 nm-TiO2 NRA.The time resolved photoluminescence spectra showed that MBI PSCs based on 564 nm had the shortst lifetime,indicating that the photoelectrons can pass from the MBI light-absorption layer to the TiO2 layer relatively easily,the carrier recombination probability becomes lower and the corresponding efficiency is higher.After 67 days,the efficiency remained almost unchanged,demonstrating excellent stability of the MBI PSCs.(2)High quality MBI films were synthesized by using two antisolvents:chlorobenzene(CB)and diethyl ether(DEE),respectively.The MBI films were used as light-absorption materials in mesoporous TiO2 PSCs.The influence on Bi-based PSCs between traditional one-step and anti-solvent treated MBI films was compared.XPS and XRD showed that MBI was synthesized.The SEM demonstrated that the DEE/MBI film had the best quality and the highest light absorption capacity with treating,and the corresponding PCE was 0.343%,We also found that PCE was over 0.3%of the 85.7%of 8 cells,demonstrating the reproducibility of the device assembled with MBE/DEE.Moreover,the PCE of DEE/MBI PSCs still remained over 0.3%after 100 days,only decreased 7.58%,indicating signicant long-term stability of this device.(3)We explored the morphology of MBI film with different voltages by pulse deposition.In the electroplating process,the first step is to deposit Bi metal film and the second step is to translate Bi film to MBI film.XRD and XPS showed that MBI film was synthesized successfully.SEM indicated that the MBI crystals were still hexagonal flakes,demonstrating that the MBI film was not compacted,and the physical parameters need to be further explored. |
PDF Full Text Request