Reducing Surface Halide Deficiency for Efficient and Stable Iodide-Based Perovskite Solar Cells

Abstract

State-of-the-art, high-performance perovskite solar cells (PSCs) contain a large amount of iodine to realize smaller bandgaps. However, the presence of numerous iodine vacancies at the surface of the film formed by their evaporation during the thermal annealing process has been broadly shown to induce deep-level defects, incur nonradiative charge recombination, and induce photocurrent hysteresis, all of which limit the efficiency and stability of PSCs. In this work, modifying the defective surface of perovskite films with cadmium iodide (CdI 2 ) effectively reduces the degree of surface iodine deficiency and stabilizes iodine ions via the formation of strong Cd−I ionic bonds. This largely reduces the interfacial charge recombination loss, yielding a high efficiency of 21.9% for blade-coated PSCs with an open-circuit voltage of 1.20 V, corresponding to a record small voltage deficit of 0.31 V. The CdI 2 surface treatment also improves the operational stability of the PSCs, retaining 92% efficiency after constant illumination at 1 sun intensity for 1000 h. This work provides a promising strategy to optimize the surface/interface optoelectronic properties of perovskites for more efficient and stable solar cells and other optoelectronic devices.

Printable CsPbI3 Perovskite Solar Cells with PCE of 19% via an Additive Strategy

“…As a result, the PCE of organic–inorganic perovskite solar cells based on ambient blade‐coating recently increased to 21.9% for an 8 mm 2 single cell. [ 16 ] Unfortunately, MA‐based perovskite solar cells suffer from poor thermal stability because of the volatile MA + cation. Replacing MA + with Cs + cations (e.g., CsPbI 3 ) has allowed for significantly improved thermal stability and a slight increase of the bandgap (≈1.7 eV), which together hold promise for efficient tandem solar cells.…”

High‐Pressure Nitrogen‐Extraction and Effective Passivation to Attain Highest Large‐Area Perovskite Solar Module Efficiency

“…Overall, the performance of slot‐die coated PSCs is still low, lagging far behind those from the other large‐scale technologies, especially the champion PCE of 21.9% from blade coating. [ 19 ] We attribute the unfavorable PCE to the complicated nature of perovskite crystallization from the precursor state and the complex processing parameters in the slot‐die coating process, including substrate temperature, dynamic flow of inks, solvent density, substrate moving speed, etc. Thus, continuously optimizing the slot‐die coating process and further improving the device performance are paramount for achieving large‐scale, roll‐to‐roll production.…”

Toward Efficient and Stable Perovskite Solar Cells: Choosing Appropriate Passivator to Specific Defects

“…At the same time, excess I − provided by CdI 2 can fill the iodide vacancy on the surface. The CdI 2 ‐modified PSC achieved a high PCE of 21.9%, exhibiting a high V oc up to 1.2 V with a smallest V oc loss of 0.31 V. [ 71 ] Beyond metal halides, halide ions were also introduced in the form of ammonium halide. Tavakoli et al utilized MACl to modulate perovskite crystallization for the purpose of optimizing the morphology of thin films with large grain.…”

“…Reproduced with permission. [ 71 ] Copyright 2020, American Chemical Society. d,e) Location of Na and F ion in the FAPbI 3 .…”