These are preliminary reports that have not been peer-reviewed. They should not be regarded as conclusive, guide clinical practice/health-related behavior, or be reported in news media as established information. For more information, please see our FAQs.
19_10_31_FAPI-PbS_merged_compressed.pdf (1.28 MB)
Chemi-Structural Stabilization of Formamidinium Lead Iodide Perovskite by Using Embedded Quantum Dots for High-Performance Solar Cells
Preprints are manuscripts made publicly available before they have been submitted for formal peer review and publication. They might contain new research findings or data. Preprints can be a draft or final version of an author's research but must not have been accepted for publication at the time of submission.
submitted on 03.11.2019 and posted on 08.11.2019by Sofia Masi, Carlos Echeverría-Arrondo, Salim K.P. Muhammed, Thi Tuyen Ngo, Perla F. Méndez, Eduardo López-Fraguas, David F. Macias-Pinilla, Josep Planelles, Juan I. Climente, Iván Mora-Seró
The extraordinary low non-radiative recombination and band gap versatility of halide perovskites have led to considerable development in optoelectronic devices. However, this versatility is limited by the stability of the perovskite phase, related to the relative size of the different cations and anions. The most emblematic case is that of formamidinium lead iodine (FAPI) black phase, which has the lowest band gap among all 3D lead halide perovskites, but quickly transforms into the non-perovskite yellow phase at room temperature. Efforts to optimize perovskite solar cells have largely focused on the stabilization of FAPI based perovskite structures, often introducing alternative anions and cations. However, these approaches commonly result in a blue-shift of the band gap, which limits the maximum photo-conversion efficiency. Here, we report the use of PbS colloidal quantum dots (QDs) as stabilizing agent for the FAPI perovskite black phase. The surface chemistry of PbS plays a pivotal role, by developing strong bonds with the black phase but weak ones with the yellow phase. As a result, stable FAPI black phase can be formed at temperatures as low as 85°C in just 10 minutes, setting a record of concomitantly fast and low temperature formation for FAPI, with important consequences for industrialization. FAPI thin films obtained through this procedure preserve the original low band gap of 1.5 eV, reach a record open circuit potential (Voc) of 1.105 V -91% of the maximum theoretical Voc- and preserve high efficiency for more than 700 hours. These findings reveal the potential of strategies exploiting the chemi-structural properties of external additives to relax the tolerance factor and optimize the optoelectronic performance of perovskite materials.