Hafnium Thin Film as a Rear Metallization Scheme for Polymer/Silicon Hybrid Solar Cells

In this work, a hafnium (Hf) thin film is introduced for the first time as the rear metallization scheme between the rear side of n-type crystalline silicon (n-Si) and Ag electrode in the poly (3, 4-ethylenedioxythiophene) doped with poly (styrenesulfonate) (PEDOT:PSS) polymer/Si hybrid solar cell. Hf thin films are uniformly deposited at room temperature by sputtering technology, showing its advantages of stable electrical sheet resistance at the atmosphere with the relative humidity of 40%. The insertion of Hf thin film reduced interfacial carrier recombination and contact resistance loss, leading to a significant improvement in the open circuit voltage (V-oc) and the fill factor (FF) of the polymer/Si hybrid solar cell. Eventually, compared with the reference device (only Ag back metallization), a higher power conversion efficiency (PCE) is obtained. This efficacy could be attributed to low work function of Hf thin film to ensure the highly transparent to electrons at the rear side of the hybrid solar cell.