Improvement of Device Performance of Organic Photovoltaics via Laser Irradiation

Laser irradiation of semiconductors has attracted considerable attention due to its important background in all kinds of applications. Unfortunately, it has rarely been applied to optimize the morphology of the active layer in organic photovoltaics (OPV). This work provided previously unavailable information about the effect of laser annealing (LA) on the morphology and function of OPV and its comparison to thermal annealing (TA). The results showed that, compared with TA, the active layer treated with LA tended to form smaller donor crystals and a face-on structure, which facilitated hole transport. Moreover, small angle neutron scattering (SANS) experiments showed that, compared to TA, acceptor phase separation was suppressed by LA and became weaker with an increase of laser intensity. Furthermore, the maximum interfacial area between the acceptor phase and its surrounding matrix was achieved with proper laser intensity, which is found to be crucial for electron transport, bimolecular recombination, and subsequent device performance. Finally, the generality of femtosecond LA on the optimization device performance of OPV including fullerene and nonfullerene systems was also investigated. The findings in this work shed light on the application of LA for the further improvement of OPV device performance.