Interface Modification for Planar Perovskite Solar Cell Using Room-Temperature Deposited Nb₂O₅ as Electron Transportation Layer

Compared with crystallized TiO₂, amorphous Nb₂O₅ has been applied in planar perovskite solar cell as electron transportation layer because of its excellent optical transmittance, low temperature preparation process, and similar Femi level with TiO₂. However, the electron transfer rate is still limited by its low electron mobility and surface defect via room-temperature deposition process. Herein, a novel double buffer layer of [6,6]-phenyl-C61- butyric acid methyl ester(PCBM)/ionic liquid([EMIM]PF₆) has been inserted between perovskite and Nb₂O₅ film. The PCBM could passive the surface of Nb₂O₅ and improve electron extraction ability. The insert of [EMIM]PF₆ could improve the hydrophilic of PCBM and decrease the dissolution of PCBM in DMF during spin-coat perovskite precursor solution. A relatively high open voltage (over 1.09 V) and conversion efficiency of 18.8% have been achieved by using a double buffer layer which is the highest PCE of Nb₂O₅ based perovskite solar cell to our best knowledge. The results indicate room temperature deposited Nb₂O₅ can be a suitable candidate for replacing crystallized TiO₂ film and proposed modification strategy could facilitate the future development of interface modified layer for high efficient planar perovskite solar cell.