Performance improvement of perovskite solar cells using vanadium oxide interface modification layer

Abstract

To improve the performance of perovskite solar cells (PSCs), vanadium oxide (VOx) film was deposited as an interface modification layer (IML) by a radio frequency magnetron sputtering system. The VOx IML was utilized to modify the interface between the indium tin oxide (ITO) anode electrode and the poly(3,4-ethylenedioxythiophene)-poly (styrene sulfonate) (PEDOT:PSS) hole transport layer (HTL). The valence band maximum (VBM) of 4.94 eV of the VOx films was measured by an ultraviolet photoelectron spectroscopy (UPS). Using the optical energy bandgap and the VBM of the VOx film, the conduction band minimum (CBM) energy level was 2.12 eV. This phenomenon verified that the VOx IML could be an electron blocking layer and made a more match energy level between the work function of ITO anode electrode and the highest occupied molecular orbital (HOMO) of PEDOT:PSS HTL. Using the measurement of contact angle, the surface energy of PEDOT:PSS HTL spun on VOx IML and ITO anode electrode was evaluated as 47.76 mJ/m2 and 38.21 mJ/m2, respectively. The enhanced surface energy of the PEDOT:PSS HTL spun on VOx IML could improve the adhesion ability of the perovskite absorption layer spun on the PEDOT:PSS HTL. Consequently, the carrier extraction could be enhanced and the leakage current could be reduced by the predominant functions of VOx IML. Therefore, the performances of the PSCs were significantly improved. The power conversion efficiency (PCE) of the PSCs with VOx IML was enhanced from 9.43% to 13.69% in comparison with the conventional PSCs without VOx IML.