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.