The role of a LiF layer on the performance of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/Si organic-inorganic hybrid solar cells

We report an ultra-thin layer of lithium fluoride (LiF) between silicon (Si) and aluminum (Al) in a Si/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hybrid solar cell which resulted in a power conversion efficiency (PCE) of 11.09%. The insertion of a thin layer of LiF improved the contact between Si and Al, which decreased the contact resistance from 5.4 × 10−1 Ω cm2 to 2.6 × 10−2 Ω cm2. Also, the electron transport from Si to Al was improved and charge carrier recombination was suppressed. As a result, the short circuit current density, the open circuit voltage, and the fill factor were all improved with the presence of the LiF layer. The solar cell with the LiF/Al bilayer as a cathode displayed a 14.45% enhancement on PCE when compared with the device using pristine Al as a cathode.