2021 Angew. Chem. Int. Ed., Open-circuit Voltage over 1.23V! How to Solve the Defect Problem of Perovskite Films?

　　Angewandte Chemie (IF 15.336) published a study in December 2021. During solution processing of organic-inorganic halide perovskite films, halide-anion-related defects, including halide vacancies and interstitial defects, readily form at the surfaces and grain boundaries. Among them,

1. The uncoordinated lead cations create defect levels within the band gap.
2. Excess iodide interferes with interfacial carrier transport

　　Therefore, these defects can lead to severe nonradiative recombination, hysteresis, and substantial energy loss in the device. Here, the research team introduced polyacrylonitrile (PAN) to passivate the uncoordinated lead cations in perovskite films. Enlitech’s QE-R Quantum Efficiency Measurement system was used to record the external quantum efficiency (EQE) and other instruments were used in this study to assist in the measurement. After comparing several common polymers, it was found that the coordination ability of cyano group is stronger than that of commonly used carbonyl groups. Strong coordination reduces the I/Pb ratio at the film surface. Therefore, with the PAN perovskite film, the device efficiency improved from 21.58% to 23.71%, the open-circuit voltage increased from 1.12 V to 1.23 V, the ion migration activation energy improved, and the operating stability also improved.

　　In addition to the EQE (External Quantum Efficiency) spectrum analysis of solar cells, the Quantum Efficiency Measurement System of Enlitech also provides Jsc (short-circuit current density) comparison for the short-circuit current of solar cells under the solar simulator to prove the authenticity of the experiment.