Researchers from Huaqiao University, City University of Hong Kong and Chinese Academy of Sciences (CAS) have explained that highly efficient perovskite solar cells in the n-i-p structure demonstrated limited operational lifetimes earlier due to the layer-to-layer ion diffusion in perovskite/doped hole-transport layer (HTL) heterojunction, leading to conductivity drop in HTL and component loss in perovskites. Now, they have reached 26.39% efficiency of perovskite solar cells using an ultrathin (~7 nm) p-type polymeric interlayer (D18) with excellent ion-blocking ability between perovskite and HTL to address these issues.
Device architecture, the structure of D18 polymer, and the detailed ion blocking effect of D18 membrane. Image credit: Nature Communications
The ultrathin D18 interlayer effectively inhibits the layer-to-layer diffusion of lithium, methylammonium, formamidium, and iodide ions. Additionally, D18 improves the energy-level alignment at the perovskite/HTL interface and facilitates efficient hole extraction.
The resulting PSCs achieved efficiencies of 26.39% (certified 26.17%) and 25.02% with aperture areas of 0.12 and 1.00 square centimeters, respectively. Remarkably, the devices retained 95.4% of the initial efficiency after 1100 hours of operation in maximum power point tracking, representing significant stability advancements for high-efficiency n-i-p PSCs.
The researchers said that the idea of incorporating a hole-selective interlayer in PSCs was inspired by proton exchange membrane (PEM) fuel cells, where the PEM serves as a proton conductor while blocking the diffusion of other chemical species.
“To achieve highly stable n-i-p PSCs with high efficiency, the inserted hole-selective interlayer is expected to efficiently transport photo-generated holes and inhibit ion diffusion,” the researchers said.
