Simple and Low-Cost Vanadyl Oxalate as Hole Transporting Layer Enables Efficient Organic Solar Cells

Organic solar cells (OSCs) with the conventional configuration usually use polyethylenedioxythiophene:polystyrene sulfonate (PEDOT:PSS) as the hole-transporting layer (HTL); however, its acidity tends to affect the performance and long-term stability of the devices. Therefore, replacing PEDOT:PSS with other more stable HTLs is essential for realizing the practical applications of OSCs. To achieve this goal, a simple and low-cost vanadyl oxalate (VOC2O4) is identified as a HTL to facilitate high power conversion efficiencies (PCEs), good stability, and high thickness tolerance to be achieved in OSCs. The VOC2O4 thin film can be easily prepared by spin-coating from its aqueous solution onto ITO/glass substrate and thermally annealed at 100 & DEG;C to exhibit high transmittance, conductivity, and work function. It can be applied as a robust HTL with wide processing conditions, especially after being heated at 200 & DEG;C and treated with UV-ozone (UVO) to afford a very high PCE of 18.94% in OSCs. This value is among the highest PCEs obtained for binary OSCs. In addition, the derived OSCs exhibit high thickness tolerance and better stability than those based on PEDOT:PSS as HTL. These results reveal that VOC2O4 is an excellent HTL for OSCs, having great potential for large-area device applications. Simple and low cost vanadyl oxalate (VOC2O4) has been identified as efficient hole transporting layer (HTL) in organic solar cells to facilitate high efficiency and stability. The robust VOC2O4 HTL can be fabricated with wide conditions, especially annealing at 200 & DEG;C and treated with UV-ozone affording a top efficiency of 18.94% with a fill factor of 80% in binary OSCs.image