High-efficiency polymer-PbS hybrid solar cells via molecular engineering

Solution-processed hybrid solar cells (HSCs), composed of conjugated polymers and semiconducting PbS nanocrystals, are promising candidates for the next-generation photovoltaic devices. Through deliberate molecular design, a series of new organic donor-acceptor polymers bearing varying optical band-gaps (1.25-1.65 eV) and suitable HOMO (highest occupied molecular orbital) energy levels (similar to 5.0 eV) were synthesized. Due to improved device architecture, we achieved the highest power conversion efficiency (PCE) of 4.23% to date for polymer-PbS based HSCs. Furthermore, the correlation between the polymer molecular structure and hybrid blend morphologies was systematically investigated using 2-dimensional grazing incidence X-ray diffraction, atomic force microscopy and scanning transmission electron microscopy. We believe our findings can be beneficial to the future molecular design toward highly efficient polymer-PbS HSCs.