Enhanced Photovoltaic Performance with Carbon Nanotubes Incorporating into Hole Transport Materials for Perovskite Solar Cells

In an attempt to further enhance the photovoltaic performance of perovskite solar cells (PSCs) fabricated by spray deposition under ambient conditions, carbon nanotubes (CNTs) are introduced for incorporation into hole transport materials (HTM). The effect of CNT category and length on the efficiency of the perovskite solar cell for incorporation into HTM is investigated. The enhanced photovoltaic performance is achieved in multi-walled carbon nanotubes (MWCNTs) with the shortest length. The efficiency of acid-treated MWCNT-based cells is improved compared to that of purified MWCNTs due to the better dispersibility and the p-p interaction between the -COOH group and spiro-OMeTAD. As the volume ratio of the spiro-OMeTAD and spiro/MWCNTs mixture is 2: 2 or 3: 1, the highest power conversion efficiency (PCE) of PSCs containing MWCNTs reaches 8.7% with the enhanced short-circuit current density (J(sc)) and open-circuit voltage (V-oc)