Complete coverage of perovskite materials over ZnO Nanorods with Multiwalled Carbon Nanotubes (MWCNTs) as Hole Transport Material (HTM)

Abstract

In this research, ZnO nanorods (NRs) have been fabricated for perovskite solar cell (PSC) application. An issue about the use of ZnO material for PSC application is lower photovoltaic outputs than TiO2 material. Such outcome is due to unstable ZnO/perovskite interface. Other factor is due to partial coverage of the perovskite over the ZnO material. By using 1-step method and mixture of DMF and DMSO as the solvent for perovskite solution, complete coverage of the ZnO NR was achieved. Multiwalled carbon nanotubes (MWCNTs) and copper iodide (CuI) were used as hole transport materials (HTMs) for comparison purpose. The experiment and characterization were done in Shizuoka University, Hamamatsu campus, Japan. The ZnO NRs were grown by implementing 2-steps method of seed layer deposition by spin coating and NRs growth through chemical bath deposition. Methylammonium lead iodide (CH3NH3PbI3 or MAPbI3) perovskite was grown through 1-step method by mixing equimolar lead iodide (PbI2) and methylammonium iodide (CH3NH3I or MAI) in DMF and DMSO solvents (volume ratio of 7 to 1 for DMF and DMSO, respectively). The current-voltage (I-V) curve for both materials showed higher JSC and VOC for MWCNTs at 5.34 mA/cm2 and 0.21 V, respectively compared to CuI materials (JSC = 3.40 mA/cm2 and VOC = 0.14 V). Lower VOC is the result of higher series resistance due to non-passivated ZnO/MAPbI3 interface. Another factor to consider is recombination of electron and hole at the interface. MWCNT material is an alternative material to act as HTM because of high conductivity and lower electrical resistance compared to CuI. Complete coverage of the perovskite over ZnO material helped improving the production of photogenerated electrons.