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

Abstract

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.