Abstract
In this thesis, we investigated that quasi-one-dimensional nanomaterials of single-walled carbon nanotubes (SWCNTs) and boron-nitride nanotubes(BNNTs) been used to enhance the photovoltaic performance and device lifetime in an organic photovoltaic (OPV) cells, respectively. In the first task, we fabricated and characterized OPV devices with hybrid composite anodes containing SWCNT networks sandwiched between ITO and PEDOT:PSS. We found that Voc of our OPV devices was insensitive to SWCNTs’ work function shifting caused by the employed chemical treatments, while Jsc and PCE both increased in the order of : reference devices < devices with pristine SWCNT networks < devices with H2SO4/HNO3-treated SWCNT networks < cells with N2H4-treated SWCNT networks. Compared to reference devices, Jsc and PCE of devices with N2H4-treated SWCNT networks were enhanced by 14% and 12%, respectively. The devices with N2H4-treated SWCNTs could lead to a maximum PCE up to 4.02%. The enhanced photovoltaic performance exhibited by our OPV devices with N2H4-treated SWCNTs could be attributed to better carrier extraction and phase segregation. Most importantly, for the first time, quasi-aligned digitation of planar networked SWCNTs into the active layer after annealing via the spontaneous penetration of multiple individual SWCNTs previously residing on a 2D structure sandwiched between ITO and PEDOT:PSS was observed in this work. The SWCNT digitation/penetration phenomenon was attributed to the minimization of free energy at the interface of the P3HT-containing active layer and the SWCNT-containing composite anode. The digitation of SWCNTs into the active layer as penetrating electrodes promote the hole-harvesting process by suppressing the SCLP effect to increase carrier mobility in P3HT, which also provides a new strategy that can be exploited for the fabrication of high-performance OPV devices.In the second task, Boron nitride nanotubes were synthesized on a large scale with iron-supported catalysts at low substrate temperatures (900 oC) with a PACVD approach using controlled gas-phase precursors (diborane and ammonia). The structural morphology, chemical composition, and optical and photoluminescence properties of BNNTs were characterized. Moreover, the role of the metal catalyst in this catalytic CVD process was investigated, and a phenomenological model of the growth mechanisms was presented. In addition, the as-grown BNNTs reveal obvious optical absorption in the UV region of the solar spectrum and are exploited for processing BNNTs loaded polymer for packaging of OPV cells in the near future. Based on this concept, the OPV cells were expected to extend the operation lifetime by suppressing the photochemistry-induced degradation.