High-performance printable hybrid perovskite solar cells with an easily accessible n-doped fullerene as a cathode interfacial layer

Engineering the interface between the active layer and the electrodes has proven to be a promising strategy to enhance the power conversion efficiency (PCE) of hybrid perovskite solar cells (PeSCs). Here, we present an effective approach to achieve highly efficient PeSCs by inserting an easy-accessible hexamethonium bromide (HMB)-doped [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) film between the active perovskite layer and the Ag cathode. This doped interfacial layer delivers several remarkable features for use in PeSCs, including solution processability, good electrical conductivity, fine work-function tunability of the Ag electrode, and general applicability to different fullerene materials. As a consequence, planar-heterojunction PeSCs deliver a PCE up to ∼18%, showing an approximately 5.6-fold enhancement compared with the control device using an undoped PC61BM layer. In particular, benefitting from the high conductivity of this doped film, a prominent PCE as high as 15.58% can be achieved even when a large thickness of the PC61BM layer (120 nm) is used. To the best of our knowledge, this is the highest performance ever reported for PeSCs with a PC61BM thickness more than 100 nm. More encouragingly, large-area PeSCs (active area = 1.2 cm2) via the doctor-blade coating technique also exhibit a remarkable PCE (15.23%) and good long-term stability under an inert atmosphere. Our results indicate that the HMB-doped PC61BM film is a promising interfacial layer for PeSCs and can be compatible with high throughput roll-to-roll manufacturing processes.