High performance and stable perovskite solar cells using vanadic oxide as a dopant for spiro-OMeTAD

Abstract

Spiro-OMeTAD as a hole-transport material (HTM) plays a crucial role in the photovoltaic performance and stability of perovskite solar cells (PSCs). However, the inferior conductivity and mediocre hole-mobility of unoxidized spiro-OMeTAD limit its function. In order to improve the functional properties of HTMs, we develop a new kind of dopant, vanadic oxide (V₂O₅) in place of the traditional oxygen in the presence of a lithium salt. V₂O₅ with strong redox potential can rapidly oxidize spiro-OMeTAD, which effectively improves the hole-transport properties and adjusts the energy level of the HTM. Consequently, the champion PSC based on the V₂O₅-doped HTM achieves a power conversion efficiency of 20.5%, while the device without V₂O₅ doping exhibits an efficiency of 18.1% under the same test conditions. Meanwhile, owing to the reduction of trap state density and the band gap adjustment by V₂O₅ doping the hysteresis of devices is effectively suppressed and the stability is improved. The facile and inexpensive treatment and obvious performance improvement render the present finding very promising.