Comparative study of electrochemically-grown vanadium pentoxide nanostructures synthesized using differential pulse voltammetry, cyclic voltammetry, and chronoamperometry methods as the hole transport layer

Vanadium pentoxide (V ₂O ₅ ) nanostructures were grown on the ITO-coated glass slides using differential pulse voltammetry (DPV), cyclic voltammetry (CV), chronoamperometry (CA) methods, and utilized as the hole transport layer (HTL) in the construction of bulk heterojunction polymer solar cells (BHJ PSCs). The influences of the deposition time in the mentioned methods were investigated to find the best conditions to achieve the highest electrochemical performance from the deposited layer. The morphology of the electrodeposited nanostructures differed by changing the applied potential regime, and V ₂O ₅ nanorods (NRDs) were formed by the CV while V ₂O ₅ nanoparticles (NPs) formed using DPV and chronoamperometry. Simple adjustment of the applied potential regime and deposition time led to considerable structural and electrochemical changes of the resulting V ₂O ₅. Features of the electrochemically-grown V ₂O ₅ were compared with each other and with those of the V ₂O ₅ prepared using the hydrothermal method. The best sample in each series was selected in terms of suitable surface conductivity, high optical transparency and appropriate energy levels and applied as HTL in BHJ PSCs. Results revealed that the V ₂O ₅ sample prepared using DPV provided considerably better electrical, optical and electrochemical features. PSCs prepared based on this sample exhibited a higher power conversion efficiency (PCE) (~ 48%) and fill factor (~2%) than PSCs prepared based on V ₂O ₅ synthesized by the hydrothermal method. This was attributed to the high electroactive surface area (0.26 ± 0.003 cm ²), high charge mobility (2.44 × 10 ^-4 cm ². V ^-1s ^-1) and excellent conductivity (0.03 mS.cm ^-1) of V ₂O ₅ NPs grown using DPV. The best cell provided an open circuit voltage of about 0.56 V, a short circuit current of 9.42 mA cm ², a fill factor of 65.3% and a power conversion efficiency of 3.40%. PCE of this cell was about 60% higher than that considered for the reference device prepared base on the PEDOT:PSS HTL.