Interface barrier strategy for perovskite solar cells realized by In-situ synthesized polyionic layer

The harmonious coordination between the perovskite and the charge transport layer is the prerequisite for the high efficiency and stability of perovskite solar cells (PSCs). The excellent photoelectric and solution processable SnO2 electron transport material opens the most commercial potential of planar PSCs. However, SnO2 has rich surface activity and photocatalytic properties, which will deteriorate perovskite after absorbing UV light and seriously affect the stability and efficiency of PSCs. Here, the interface barrier strategy is introduced to insert an anchored-then-rinsed lead polystyrene sulfonate (ARPSS-Pb) polyionic layer between SnO2 and perovskite via in-situ synthesis method to construct a new stable interface, which can effectively block the phase transition of perovskite driven by photocatalytic SnO2. In addition, ARPSS-Pb also has the functions of passivating interfacial defects, relaxing interfacial stress and guiding crystallization of perovskite. PSCs based on ARPSS-Pb achieved a power conversion efficiency (PCE) of 22.26%, much higher than 19.60% of the control devices. More importantly, after 1000 h of storage under continuous humidity conditions, up to 96.32% of the initial PCE is maintained. A high open circuit voltage (VOC) as high as 1.190 V has been obtained for ARPSS-Pb based devices. To our best knowledge, this is the highest VOC achieved in the system of perovskite with 1.56 eV energy gap.