CsPbI3 perovskite quantum dots (QDs) are more unstable over time as compared to other perovskite QDs, owing to ligand loss and phase transformation. The strong red emission from fresh CsPbI3 QDs gradually declines to a weak emission from aged QDs, which PLQY dropped by 93% after a 20 day storage; finally, there is no emission from δ-phase CsPbI3. The present study demonstrated a facile surface treatment method, where a sulfur–oleylamine (S-OLA) complex was utilized to passivate the defect-rich surface of the CsPbI3 QDs and then self-assembly to form a matrix outside the CsPbI3 QDs protected the QDs from environmental moisture and solar irradiation. The PLQY of the treated CsPbI3 QDs increased to 82.4% compared to initial value of 52.3% of the fresh QDs. Furthermore, there was a significant increase in the colloidal stability of the CsPbI3 QDs. Above 80% of the original PLQY of the treated QDs was reserved after a 20 day storage and the black phase could be maintained for three months before transforming to the yellow phase. The introduction of S-OLA induced the recovery of the lost photoluminescence of the nonluminous aged CsPbI3 QDs with time to 95% of that of the fresh QDs. Furthermore, the photoluminescence was maintained for one month. The increase in the stability and photoluminescence are critical for realizing high-performance perovskite-QD-based devices. Therefore, this work paves the way for increasing the performance of perovskite-based devices in the near future.

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Metal-organic frameworks (MOFs) and MOF-derived materials have been used for several applications, such as hydrogen storage and separation, catalysis, and drug delivery, owing to them having a significantly large surface area and open pore structure. In recent years, MOFs have also been applied to thin-film solar cells, and attractive results have been obtained. In perovskite solar cells (PSCs), the MOF materials are used in the form of an additive for electron and hole transport layers, interlayer, and hybrid perovskite/MOF. MOFs have the potential to be used as a material for obtaining PSCs with high efficiency and stability. In this study, we briefly explain the synthesis of MOFs and the performance of organic and dye-sensitized solar cells with MOFs. Furthermore, we provide a detailed overview on the performance of the most recently reported PSCs using MOFs.

Planar perovskite solar cells were fabricated on F-doped SnO2 (FTO) coated glass substrates, with 4,4’-((1E,1’E)-((1,2,4-thiadiazole-3,5-diyl)bis(azaneylylidene))bis(methaneylylidene))bis(N,N-di-p-tolylaniline) (bTAThDaz) as hole transport material. This imine was synthesized in one step reaction, starting from commercially available and relatively inexpensive reagents. Electrochemical, optical, electrical, thermal and structural studies including thermal images and current-voltage measurements of the full solar cell devices characterize the imine in details. HOMO-LUMO of bTAThDaz were investigated by cyclic voltammetry (CV) and energy-resolved electrochemical impedance spectroscopy (ER-EIS) and were found at −5.19 eV and −2.52 eV (CV) and at −5.5 eV and −2.3 eV (ER-EIS). The imine exhibited 5% weight loss at 156 °C. The electrical behavior and photovoltaic performance of the perovskite solar cell was examined for FTO/TiO2/perovskite/bTAThDaz/Ag device architecture. Constructed devices exhibited good time and air stability together with quite small effect of hysteresis. The observed solar conversion efficiency was 14.4%.

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.