Phenanthroline-carbolong interface suppress chemical interactions with active layer enabling long-time stable organic solar cells

To restrain the chemical reaction at cathode interface of organic solar cells, two cathode interfacial materials are synthesized by connecting phenanthroline with carbolong unit. Consequently, the D18:L8-BO based organic solar cell with double-phenanthroline-carbolong achieve the highest efficiency of 18.2%. Double-phenanthroline-carbolong with larger steric hindrance and stronger electron-withdrawing property confirms to suppress the interfacial reaction with norfullerene acceptor, resulting the most stable device. Double-phenanthroline-carbolong based device can sustain 80% of its initial efficiency for 2170 h in dark N2 atmosphere, 96 h under 85 oC and keep 68% initial efficiency after been illuminated for 2200 h, which are significantly better than bathocuproin based devices. Moreover, superb interfacial stability of double-phenanthroline-carbolong cathode interface enables thermal posttreatment of organic sub-cell in perovskite/organic tandem solar cells and obtained a remarkable efficiency of 21.7% with excellent thermal stability, which indicates the potentially wide application of phenanthroline-carbolong materials for stable and efficient solar device fabrications.