Recombination Dynamics as a Key Determinant of Open Circuit Voltage in Organic Bulk Heterojunction Solar Cells: A Comparison of Four Different Donor Polymers

Transient photovoltage and charge extraction analyses are employed to analyzes charge carrier densities and bimolecular recombination dynamics in organic polymer: fullerene solar cells under open circuit operating conditions, employing four different donor polymers. An equation is derived which allows us to calculate the device VOC from these kinetic measurements. This equation allows us to calculate voltage output of devices within ± 25 meV of directly measured values. This analysis thus allows us to relate device open circuit voltage directly to the kinetics of bimolecular recombination, and thereby the influence of nanomorphology upon device voltage output.