Highly efficient cross-linked PbS nanocrystal/C60 hybrid heterojunction photovoltaic cell

We present a highly efficient hybrid heterojunction photovoltaic (PV) cell with a colloidal inorganic nanocrystal (NC) electron donor and an organic electron acceptor. The heterojunction is formed by a thin film of cross-linked PbS NCs and a C₆₀ layer. Compared to the PbS-only PV cell, the heterojunction device has improved the power conversion efficient (PCE) from 1.6 % to 2.2 %. The C₆₀ layer effectively prevents the excitons from quenching at the NC/metal interface, which is demonstrated with a significant improvement of the fill-factor (FF) of the heterojunction devices. In addition, a larger open-circuit voltage (V_OC) in the heterojunction devices suggests that the electrons in C₆₀ can readily transfer to the PbS NCs through the NC surface linkers. This is supported by the measured optical absorption spectrum of the hybrid system.