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

Abstract

Vanadium pentoxide (V2O5) 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 V2O5 nanorods (NRDs) were formed by the CV while V2O5 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 V2O5. Features of the electrochemically-grown V2O5 were compared with each other and with those of the V2O5 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 V2O5 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 V2O5 synthesized by the hydrothermal method. This was attributed to the high electroactive surface area (0.26±0.003 cm2), high charge mobility (2.44 × 10-4 cm2. V-1s-1) and excellent conductivity (0.03 mS.cm-1) of V2O5 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 cm2, 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.