Trap-Filling-Induced Charge Carrier Dynamics in Organic Solar Cells

Traps, which are inevitable in organic solar cells, will result in trap-assisted recombination, an important loss mechanism that limits device performance. Trap-filling is an efficient approach to suppress the charge traps, and can improve charge transport and modify the electronic properties. This approach fills the defect states where traps reside by introducing additional carriers, rendering the states electronically inert. Herein, charge carrier dynamics in the prototypical system PCE10/PC₇₁BM with/without doping at different concentrations is directly targeted by employing transient absorption spectroscopy. It is found that the charge carriers' lifetime enhances, and the recombination centers can be filled at high doping concentrations, which is beneficial for achieving high power conversion efficiency. These findings indicate that charge transport and electronic characteristics can be improved by trap-filling, which is the key to pushing the efficiencies of organic solar cells toward theoretical limits.