Rationalizing charge carrier transport in ternary organic solar cells

Ternary bulk heterojunction (BHJ) organic solar cells have energy offsets between multiple donors and acceptors. In such bi-continuous percolating films, electron carriers mainly transport in acceptor materials, and hole carriers typically transport in donor materials. Changing the third component of additional donors or acceptors is a common method to fine-tune the transport properties in ternary BHJs. Experimentally, although there are some empirical guidelines for the mobility evaluation, a clear charge transporting model has still not been fully established in multi-component BHJ films. Herein, we observed a general regularity about charge transport that the charge carriers have higher possibilities to transport in polymeric materials even if only low dosage (<10% in weight) polymeric materials are introduced for both the hole and electron cases. From the extended Su-Schrieffer-Heeger model, a polymer bridge assisted charge transport mode in small molecules is proposed after the energy offset exceeds the threshold (Delta E-e > 0.15 eV). This work provides a perspective for fine tuning the charge transport property in high-performance ternary organic solar cells. Published under an exclusive license by AIP Publishing.

Automated summary

Ternary bulk heterojunction organic solar cells have energy offsets between multiple donors and acceptors. This study observed that charge carriers have higher possibilities to transport in polymeric materials, even in low dosage. A polymer bridge assisted charge transport mode in small molecules is proposed after the energy offset exceeds the threshold.