Controllable power-conversion efficiency in organic-solar cells

In organic donor–acceptor structures, the efficiency is largely controlled by a fundamental photophysics process. Herein, the excited state dynamics of a conjugated polymer PBDT(X)TPD with ring substituents are explored using femtosecond transient absorption spectroscopy (fs-TA). The brilliant measuring sensitivity of our instruments has allowed us to study the influence of the substituted side group on charge dynamics as well as the device performance. fs-TA data demonstrates a clear correlation between the ultrafast charge separation and charge recombination, fluorescence quantum yields, ring substitutions, and device performance. Thus, the careful selection of side groups can make huge changes in the photo-electronic properties of polymers.