The Study On Hole-conductor-free Perovskite Solar Cells With Carbon Counter Electrodes Based On TiO₂ Nanorod Arrays

With the depletion of traditional fossil energy sources,people have turned to the development and utilization of new energy sources.From the initial silicon-based solar cells to today's dye-sensitized solar cells(DSSCs)and perovskite solar cells(PSCs),PSCs have been extensively studied for their advantages of all-solid-state safety and simple manufacturing processes.To date,the photoelectric conversion efficiency of PSCs has exceeded 20%.In the traditional PSCs structure,hole transport material(HTM)and precious metal counter electrode are usually included.The use of HTM and precious metals will undoubtedly increase the production cost of the cells.In order to reduce the cost of the PSCs and simplify the manufacturing process,the researchers used a screen printing technology to prepare PSCs.Among them,Han's research group directly applied TiO2 layer,ZrO2 layer and C layer on the FTO conductive glass covered with seed layer by screen printing technology,and then dripped the precursor of perovskite directly,obtained more than 12%of the photoelectric conversion efficiency,which was hope for industrialization.In order to further reduce the production cost of PSCs,we consider using low-temperature C to instead of C-slurry required high-temperature annealing,and omitting the ZrO2 layer,which made the structure of the cells simpler.Considering that TiO2-NR have faster electron transport rate and light scattering ability than TiO2 particles,the TiO2-NR were prepared by hydrothermal method as electron transport layer materials and assembled into the PSCs with free-hole transport layer and carbon as counter electrode.The effects of TiO2-NR on the performance of PSCs under different hydrothermal conditions were studied.The details of the work are as follows:(1)The PSCs based TiO2-NR and C as electrode was prepared,and studied the effect of arrays parameters on cells performance.T1O2-NR were grown on FTO conductive glass covered with seed layer by hydrothermal method.The nanorod arrays grown under different hydrothermal conditions were characterized by SEM,and the growth process of nanometer TiO2 under different hydrothermal conditions was discussed.TiO2-NR grrown under different hydrothermal conditions were assembled into perovskite solar cells(specific structure:FTO/ETL/TiO2-NR/ZrO2/C),and the perovskite precursor solution was dropped from the carbon layer,performing a J-V performance test after annealing.The experimental results show that the performance of the cells is affected by the pore size of the arrays and the length of the TiO2 nanorods.The TiO2-NR grown under hydrothermal conditions of 140?/3h were assembled into PSCs.The open circuit voltage of the cell was 0.85 V,the short-circuit current density was 18.59 mA/cm2,and the photoelectric conversion efficiency reached 7.5%.(2)In order to further reduce the production cost of the PSCs,we removed the ZrO2 layer on the basis of the study(1),prepared the MAPbl3 light absorbing layer with good crystallinity by the anti-solvent method,and used the low temperature C to instead of the carbon slurry that required high temperature annealing.The two-step annealing step is omitted,the manufacturing process becomes simpler,and the prepared cells have a simpler structure(specific structure:FTO/ETL/TiO2-NR/MAPbI3/C).Based on the results of(1),TiO2-NR grown under hydrothermal conditions of 140?/2h and 140?/3h were assembled into the PSCs with low temperature carbon as counter electrode.The PL measurements of the TiO2-NR show that the nanorod arrays prepared under hydrothermal conditions at 140?/2h has a faster electron injection rate.As well as J-V performance test of the PSCs,the experimental results show that the assembled PSCs with TiO2-NR prepared under the hydrothermal conditions of 140?/2h has a higher short-circuit current density.The J-V performance of the PSCs was tested,the experimental results show that the PSCs assembled with TiO2-NR prepared under the hydrothermal conditions of 140?/2h has a higher short-circuit current density,and the average short-circuit current density reaches a high level of 17.16,m A/cm2,which is more than the short-circuit current density of 13.56 mA/cm2 of the PSCs with TiO2-NR grown under hydrothermal conditions of 140?/3 h.The PSCs obtained highest photoelectric conversion efficiency of 7.2%based on the TiO2-NR as electron transport layer material under hydrothermal conditions of 140?/2h,and the average photoelectric conversion efficiency was 6.2%.