Dopant-free hole conductor with hybrid multisite passivation for perovskite solar cells

[Display omitted] •Hybrid multisite passivation were introduced for multi-functional small molecular HTMs.•The passivation effect of carbonyl can be strengthened by introducing nitrogen.•Hole mobility is 71% higher and hole trap-density is 49% lower by the strategy. Polymer hole-transporting material (HTM) with multi-site anchors is an interesting idea for defect passivation in perovskite solar cells (PSC). In this work, a small molecular HTM coded as TPA-DN with hybrid multisite passivation, that is two chelated pyridine nitrogen atoms and carbonyl double anchor sites, is developed. Two nitrogen atoms with higher electronegativity in TPA-DN can chelate with uncoordinated lead in perovskite, and the electron cloud density of oxygen in carbonyl can be increased by introducing nitrogen in fluorene-9-one core. The hole mobility is 71% higher and the hole trap-density is 49% lower after introducing the hybrid multisite passivation strategy. Comparing with the analogue without chelated nitrogen atoms, TPA-DN causes the power conversion efficiency (PCE) increasing from 18.37% to 19.45% with increased short-circuit current density and open-circuit voltage, respectively. This work proves that hybrid multisite passivation is an effective strategy in the design of organic p-type semiconductors.