Researchers at South Korea’s Ulsan National Institute of Science and Technology (UNIST) and Pohang University of Science and Technology report a power conversion efficiency of 25.8% for a single junction perovskite solar cell, by forming a coherent interlayer between electron-transporting and perovskite layers to reduce interfacial defects.

The cell was built with an interlayer between a tin(IV) oxide (SnO2) electron-transporting layer and a layer made of a halide perovskite layer by coupling chlorine-bonded SnO2 with a perovskite precursor containing chlorine. “This interlayer has atomically coherent features which enhance charge extraction and transport from the perovskite layer; and fewer interfacial defects,” the academics explained.

The defect-free connection layer is said to eliminate the risks related to passivation, which may not always provide the desired interface defect reduction, as the surface-treatment agents on the electron-transporting layer may dissolve while coating the perovskite thin film.

The cell also reportedly retained around 90% of its initial efficiency after 500 hours under standard illumination. “Our findings provide guidelines for designing defect-minimizing interfaces between metal halide perovskites and electron-transporting layers,” said UNIST researcher Seok Sang-il.

In April 2021, researchers from UNIST and the Swiss Federal Institute of Technology Lausanne (EPFL) achieved a conversion efficiency of 25.6% in a single-junction perovskite solar cell. The result also surpasses the previous record of 25.2%, achieved in February by scientists at the Massachusetts Institute of Technology (MIT), and UNIST's earlier result of 25.17%, achieved in November 2020.