Polymer solar cells with enhanced open-circuit voltage and efficiency

摘要

Following the development of the bulk heterojunction1 structure,recent,years have seen a dramatic improvement in the efficiencyof polymer solar cells. Maximizing the open-circuit voltage in alow-bandgap polymer is one of the critical factors towardsenabling high-efficiency solar cells. Study of the relationbetween open-circuit voltage and the energy levels of thedonor/acceptor2 in bulk heterojunction polymer solar cells hasstimulated interest in modifying the open-circuit voltage bytuning the energy levels of polymers3. Here, we show that theopen-circuit voltage of polymer solar cells constructed based onthe structure of a low-bandgap polymer, PBDTTT4, can be tuned,step by step, using different functional groups, to achieve valuesas high as 0.76 V. This increased open-circuit voltage combinedwith a high short-circuit current density results in a polymersolar cell with a power conversion efficiency as high as 6.77%,as certified by the National Renewable Energy Laboratory.