Highly efficient aqueous-processed polymer/nanocrystal hybrid solar cells with an aqueous-processed TiO2 electron extraction layer

In this work, a novel environmentally friendly approach to deposit TiO2 films via an aqueous process is developed. The atomic force microscopy (AFM) measurement indicates that water-dispersed TiO2 nanocrystals (NCs) show excellent film-forming properties on an ITO-coated glass substrate. In addition, the femtosecond transient absorption (TA) and conductivity measurements suggest that the aqueous-processed TiO2 film shows excellent electron extraction ability and good conductivity. The aqueous-processed polymer/NC hybrid solar cells based on the aqueous-processed TiO2 electron extraction layer present superior photovoltaic performance and a PCE of 5.53% is achieved, which is the highest for hybrid solar cells fabricated via an aqueous process. Finally, the solar cells with the aqueous-processed TiO2 electron extraction layer exhibit better humidity resistance compared to the TiO2 film deposited via a sol-gel method.