Simultaneous Optimization of Charge Transport Properties in a Triple-Cation Perovskite Layer and Triple-Cation Perovskite/Spiro-OMeTAD Interface by Dual Passivation

Abstract

Molecular engineering of additives is a highly effective method to increase the efficiency of perovskite solar cells by reducing trap states and charge carrier barriers in bulk and on the thin film surface. In particular, the elimination of undercoordinated lead species that act as the nonradiative charge recombination center or contain defects that may limit interfacial charge transfer is critical for producing a highly efficient triple-cation perovskite solar cell. Here, 2-iodoacetamide (2I-Ac), 2-bromoacetamide (2Br-Ac), and 2-chloroacetamide (2Cl-Ac) molecules, which can be coordinated with lead, have been used by adding them into a chlorobenzene antisolvent to eliminate the defects encountered in the triple-cation perovskite thin film. The passivation process has been carried out with the coordination between the oxygen anion (−) and the lead (+2) cation on the enolate molecule, which is in the resonance structure of the molecules. The Spiro-OMeTAD/triple-cation perovskite interface has been improved by surface passivation by releasing HX (X = I, Br) as a byproduct because of the separation of alpha hydrogen on the molecule. As a result, a solar cell with a negligible hysteresis operating at 19.5% efficiency has been produced by using the 2Br-Ac molecule, compared to the 17.6% efficiency of the reference cell.

Thermal Stability Analysis of Formamidinium–Cesium‐Based Lead Halide Perovskite Solar Cells Fabricated under Air Ambient Conditions

“…Various approaches have been utilized to address the thermal degradation issues in halide perovskite materials. These include opting for thermally stable halide perovskite materials such as FAPbI 3 , CsPbI 3 , and so on, [27][28][29] incorporating additives, [30][31][32][33][34][35][36] employing passivation layers, [37,38] fine-tuning of the material composition, and so on. [39][40][41] It has been reported that FAPbI 3 -based PSCs are thermally stable at 85 °C temperature and it maintained 85% of its initial PCE up to 400 h. [42,43] However, the challenges that FAPbI 3 faces are that at room temperature it undergoes phase transition from photoactive black perovskite phase to photoinactive hexagonal nonperovskite phase.…”