Search

In this research, we examined the impact of solution concentration on the photovoltaic and the material properties of perovskite solar cells (PSCs) obtained from dehydrated Pb-acetate precursors. The perovskite solution was deposited by a one-step spin-coating technique followed by 5 min of thermal annealing on a hotplate at the temperature of 90 °C to form the perovskite active layer. The PSC device structure adopted was the inverted planar architecture. The precursor solution concentrations were varied from 0.7 to 1.1M, with the optimal solution concentration found to be 1.0M. This concentration results in a power conversion efficiency of 12.2%, an open circuit voltage (Voc) of 0.94 V, a short circuit photocurrent density (Jsc) of 20.71 mA/cm2, and a fill factor of 62.69%. Our investigations revealed that the precursor solution concentration had a huge effect on the quality of the perovskite film and the photovoltaic properties of the PSCs.

One route to a brighter global energy future may be through enhancing the efficiency and stability of perovskite solar cells (PSCs), which depends on the level of defects in the photoactive absorber and along the interfaces of the multilayered structure. Here, we use a combined experimental and theoretical approach to study the effects of pressure-induced compaction of microvoids and closure of cracks on the power conversion efficiency (PCEs) and stability of formamidinium-rich PSCs. A range of mechanical pressures was applied to the PSCs to reduce pre-existing grain-boundary voids and interfacial cracks within the devices. The PCEs of the PSCs increased from ~19.5% to ~ 23.5% for applied pressures between ~ (0 – 7) MPa. Unlaminated device stability increased by 33%, falling to 80% of initial PCE in 1800 hrs without compression, as compared to 2400 hrs with compression. The implications of this study are discussed in light of possible future manufacturing processes.

This paper presents the results of a combined experimental and analytical/computational study of the effects of pressure on photoconversion efficiencies of perovskite solar cells (PSCs). First, an analytical model is used to predict the effects of pressure on interfacial contact in the multilayered structures of PSCs. The PSCs are then fabricated before applying a range of pressures to the devices to improve their interfacial surface contacts. The results show that the photoconversion efficiencies of PSCs increase by ~40%, for applied pressures between 0 and ~7 MPa. However, the photoconversion efficiencies decrease with increasing pressure beyond ~7 MPa. The implications of the results are discussed for the fabrication of efficient PSCs.

In this study, we reported a low-temperature, one-step solution process to fabricate perovskite solar cells using dehydrated lead acetate as the lead source. These perovskite films were aged at 200 s before thermal annealing at 90 °C for 5 min. Uniform perovskite films with lesser pinholes were obtained by this technique. The inverted planar (n-i-p) perovskite solar cell device resulted in a power conversion efficiency of 13%. A substantial finding was that the devices demonstrated high reproducibility. We also investigated the effect of annealing temperature on the optical and structural properties of the films and on the photovoltaic performances of the fabricated solar cell devices. For the aforementioned, a low-temperature, one-step solution process, the optimal temperature was achieved at 90 °C.

Incorporation of cesium (Cs) into the perovskite layer has become a good strategy to boost the stability and power conversion efficiency (PCE) of perovskite solar cells (PSCs). However, a suitable and scalable method of Cs incorporation in a perovskite film that does not cause a significant increase in the optical bandgap is needed. In this paper, we introduce a thin layer of CsBr into a formamidinium (FA)-rich mixed halide perovskite film using the thermal evaporation technique. The effects of the thickness of the CsBr layer on the microstructural, structural, and optoelectronic properties and surface chemical states of the perovskite film are then studied. The results indicate that the CsBr layer thickness is able to tune the microstructural and optoelectronic properties of the perovskite film. Planar PSCs fabricated with different thicknesses of CsBr layers in the perovskite absorber exhibited different photovoltaic performance characteristics. The CsBr-modified PSC device with a 50 nm layer of CsBr in the perovskite layer showed a better PCE of 16.19% ± 0.17%, which was about 15% higher than that of the control device, and was able to retain nearly 70% of its initial PCE value after 120 days of storage in an unencapsulated state.

This paper presents the results of experimental and theoretical studies of the effects of pressure and thermal annealing on the photo-conversion efficiencies (PCEs) of polymer solar cells with active layers that consist of a mixture of poly(3-hexylthiophene-2,5-diyl) and fullerene derivative (6,6)-phenyl-C61-butyric acid methyl ester. The PCEs of the solar cells increased from ∼2.3% (for the unannealed devices) to ∼3.7% for devices annealed at ∼150 °C. A further increase in thermal annealing temperatures (beyond 150 °C) resulted in lower PCEs. Further improvements in the PCEs (from ∼3.7% to ∼5.4%) were observed with pressure application between 0 and 8 MPa. However, a decrease in PCEs was observed for pressure application beyond 8 MPa. The improved performance associated with thermal annealing is attributed to changes in the active layer microstructure and texture, which also enhance the optical absorption, mobility, and lifetime of the optically excited charge carriers. The beneficial effects of applied pressure are attributed to the decreased interfacial surface contacts that are associated with pressure application. The implications of the results are then discussed for the design and fabrication of organic solar cells with improved PCEs.

This paper presents the results of pressure-effects on performance characteristics of near-infra-red perovskite light emitting diodes (PeLEDs) using a combination of experimental and analytical/computational approaches. First, pressure-effects are studied using models that consider the deformation and contacts that occur around interfacial impurities and interlayer surface roughness in PeLEDs. The predictions from the model show that the sizes of the interfacial defects decrease with increasing applied pressure. The current–voltage characteristics of the fabricated devices are also presented. These show that the PeLEDs have reduced turn-on voltages (from 2.5 V to 1.5 V) with the application of pressure. The associated pressure-induced reductions in the defect density and the bandgaps of the perovskite layer are then used to explain the improved performance characteristics of the PeLED devices.

In this research, we demonstrated the use of hafnium acetylacetonate (Hfaca) dissolved in ethanol as a buffer layer for perovskite solar cells from non-halide Pb (dehydrated lead acetate) source material. The inverted p-i-n planar heterojunction structure was employed in this work. A one step spin-coating method was used in depositing the perovskite solution before thermal annealing at 90 °C for 5 min to form the perovskite film. Hfaca has been previously used as a buffer layer, but the optimal concentration has not been reported. The optimum concentration of Hfaca was found to be 1.0 mg/ml, resulting in a power conversion efficiency (PCE) of 12.23% corresponding to more than 30% improvement when compared to the control device (phenyl-C61-butyric acid methyl ester/Ag) without Hfaca, which has a PCE of 8.89%. Hfaca as a buffer layer leads to superior stability, retaining about 90% of its original PCE values after 15 days of storage in a glove box, compared to the control device, which retains 70% of the initial PCE value under the same storage.