A Facile Two-Step Interface Engineering Strategy To Boost the Efficiency of Inverted Ternary-Blend Polymer Solar Cells over 10%

A facile two-step strategy was proposed to modify ZnO nanoparticle electron transfer layer in inverted ternary-blend polymer solar cells (TPSCs) by irradiating the ZnO with UV-ozone (UVO) and then spin-coating on it a poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) interfacial modification layer. The combination of UVO and PFN showed the advantage of simultaneously passivating the defect states of ZnO to reduce the defect-assisted electron hole recombination, modifying the surface morphology and hydrophilicity of ZnO to improve the interfacial contact with the active layer, and optimizing the electron transfer characteristic of ZnO to enhance the electron extraction from the active layer to the cathode. As a result, the champion power conversion efficiency of TPSCs with PTB7-Th:PCDTBT:PC70BM as the active layer was increased from 6.80% to 9.61% by 20 min of UVO irradiation and then further increased to 10.87% after the incorporation of an ultrathin PFN interfacial layer. Because of the ease of fabrication and remarkable boost in efficiency, our results indicate that this two-step strategy provides a simple and effective way to fabricate highly efficient inverted PSCs.