Role of Additives on the Performance of CsPbI₃ Solar Cells

Abstract

The role of additives in the performance of CsPbI3 perovskite solar cells (PSCs) was investigated. Different kinds of cations and anions were used as additives in a N,N-dimethylformamide (DMF) solution containing CsI and PbI2 (1:1 molar ratio). These include HI, HBr, HCl, NH4I, NH4Br, and NH4Cl. Additive cations (H+ and NH4 +) as well as halide ions (I–, Br–, and Cl–) are important for the properties of PSCs. Especially, the addition of iodine ion showed good characteristics compared to Br– and Cl–. Among the CsPbI3 layers prepared with different kinds of additives and annealed at different temperatures, the X-ray diffraction peaks of CsPbI3 were clearly found at 14° and 28° for the sample annealed at 150 °C with 50 μL of HI, suggesting the formation of a cubic structure at the low temperature of 150 °C. The field emission scanning electron microscopy images indicate that the surface of the perovskite layer with hydrogen halide additive (“H+”-based additive) is more uniform than that with ammonium additive. The roughness profiles determined by atomic force microscopy indicate that the CsPbI3 film with HI additive shows the least roughness among the samples with H+-based additives. Therefore, the best power conversion efficiency (PCE) of 4.72% is obtained for CsPbI3 PSCs annealed at 150 °C with HI (50 μL). The H+-based additives seem to react with PbI2 in DMF solution, increasing the solubility of PbI2 and thus lowering the processing temperature. Furthermore, the PCE of CH3NH3PbI3–x Cl x PSCs decreased from 7.45 to 0.23%, whereas that of CsPbI3 PSCs with 50 μL of HI only decreased from 3.55 to 2.78% after exposing the samples to air for 3 h. These results indicate that H+-based additives, especially HI, have more impact on the CsPbI3 PSCs in terms of lowering the processing temperature and improving the performance.

Metal-Organic Framework Materials for Perovskite Solar Cells

“…Therefore, recent PSC-based researchers have focused on improving the stability as well as the efficiency [ 103 , 104 ]. Studies have been performed to enhance the crystallinity, using inorganic ions [ 105 , 106 , 107 ], additives [ 108 , 109 , 110 ], new ETLs or HTLs [ 111 , 112 ], and interlayers [ 113 , 114 ].…”

Out‐of‐Glovebox Integration of Recyclable Europium‐Doped CsPbI3 in Triple‐Mesoscopic Carbon‐Based Solar Cells Exceeding 9% Efficiency

“…For this reason, the perovskite material is not prepared in ambient air but N 2 ‐filled glovebox, [ 13 ] hindering the chances for scaling up and future commercialization. To overcome this issue, different strategies have been implemented like the use of dopants [ 14 ] (organic, inorganic, elemental doping) in the CsPbI 3 precursor solution which improves the morphological and structural properties of the CsPbI 3 thin film, [ 15 ] resulting in better stability in air and enhanced device performances.…”

Chemical Composition and Phase Evolution in DMAI-Derived Inorganic Perovskite Solar Cells

“…Therefore, the improvement of the lattice symmetry and reduction of the lattice strain are the two directions to dissolve the problem of phase instability. − The nanocrystal-induced phase stabilization is one strategy to reduce the lattice strain by increasing the surface area of the crystals in the film, which is normally realized by introducing organic long-chain alkyl amine in the precursor solution. , The shortcoming of this method is its negative effect of a large number of grain boundaries on the carrier transport and injection. Currently, the most widely used and effective strategies are the DMAI-related methods, − including the DMAI additive methods and the HI derived methods. The HI derived methods, normally named HI additive, HI·PbI 2 , or HPbI 3 precursor, are demonstrated to inevitably bring the DMA byproduct in the precursor solution from the reaction between HI and DMF. , …”