16% efficiency all-polymer organic solar cells enabled by a finely tuned morphology via the design of ternary blend

A SUMMARY There is an urgent demand for all-polymer organic solar cells (AP-OSCs) to gain higher efficiency. Here, we successfully improve the performance to 16.09% by introducing a small amount of BN-T, a B <- N-type polymer acceptor, into the PM6:PY-IT blend. It has been found that BN-T makes the active layer, based on the PM6:PY-IT:BN-T ternary blend, more crystalline but meanwhile slightly reduces the phase separation, leading to enhancement of both exciton harvesting and charge transport. From a thermodynamic viewpoint, BN-T prefers to reside between PM6 and PY-IT, and the fraction of this fine-tunes the morphology. Besides, a significantly reduced nonradiative energy loss occurs in the ternary blend, along with the coexistence of energy and charge transfer between the two acceptors. The progressive performance facilitated by these improved properties demonstrates that AP-OSCs can possibly comparably efficient with those based on small molecule acceptors, further enhancing the competitiveness of this device type.

Automated summary

The performance of all-polymer organic solar cells has been improved by introducing a small amount of BN-T, resulting in increased crystallinity and enhanced exciton harvesting and charge transport. This enhancement is attributed to the reduced nonradiative energy loss and improved energy and charge transfer between acceptors, making AP-OSCs potentially as efficient as devices based on small molecule acceptors.