Methylammonium lead iodide (CH3NH3PbI3) based perovskite having low degrees of the disorder is of great interest for optoelectronic and photovoltaic applications. In this work, a layer of CH3NH3PbI3 ...was successfully prepared using an ultrasonically sprayed-nebulous method. Changes in structural and optical properties alongside with photo-induced charge separation and transportation behavior were systematically studied. The surface photovoltage spectra reveal a significant reduction of the density of deep defect states as the organic content was increased. It was observed that the measured values of Urbach energies decrease from 33.36 to 28.24 meV as the amount of organic content was increased to an optimum value. The best perovskite solar cells obtained using the sprayed-on approach exhibited a Jsc of 16.54 mA/cm2, a Voc of 0.99 V, and a FF of 62.4, resulting in an overall PCE of 10.09%.
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•Fabrication of sequence sprayed-on perovskite layers was demonstrated.•An Urbach tail energy of the sprayed films depends significantly on the exposure time to the MAI.•PSCs with a sprayed-on approach showed the PCE of 10.09%.
It is well known that thermal annealing of region-regular poly(3-hexylthiophene-2,5-diyl) and 6,6-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) solar cells helps in improving their overall ...performance. When aluminum (Al) is used as the electrode, it has been found that annealing causes the Al atoms to diffuse into the organic layer and to form what is called a "mixed layer". In this work, we studied the diffusion of Al and using Fick's second law, calculated its diffusivity in a P3HT:PCBM heterojunctions layer. By employing energy dispersive X-ray spectroscopy elemental mapping, a diffusion constant of about 1.8 × 10−21 cm2 s−1 for devices annealed at 120 °C was obtained.
An understanding of the spectrum–property relationship of perovskite solar cells when illuminated by light‐emitting diodes that are used for indoor applications is necessary. Herein, it is aimed to ...explore the influences of correlated‐color temperatures on a MAPbI3‐based device under low‐light conditions. Given an irradiance of approximately 3 W m−2 (or ≈1000 lx), a maximum free carrier generation rate of 1.0 × 1021 m−3 s−1 was found. Additionally, power conversion efficiencies (PCEs) up to 31.97%, 30.36%, and 28.98% with maximum power outputs of 13.66, 13.02, and 16.09 μW could be reached at 3000, 4000, and 6500 K, respectively. Additional increases in the PCEs were observed when high‐energy blue light (in a range of 400–550 nm) was excluded during the current–voltage sweeps. In combination with the surface photovoltage measurements, intense blue light (under 6500 K) had a minimal influence on the photoinduced charge separation signals when compared to those caused by 3000 and 4000 K light. As a solar cell, the PCE reached as high as 34.52%, which corresponded to 73.08% of the thermodynamic limit of its bandgap at 3000 K.
Herein, the impacts of the correlated‐color temperatures (CCTs) of LEDs on a single‐cation perovskite material MAPbI3 are highlighted. Based on the irradiant spectrum, an emphasis is placed on the theoretical prediction of the free carrier generation rate and maximum current density as a function of the CCT.
As a promising material, Cs4PbX6 (X = Cl, Br, I) nanocrystals (NCs) have attracted much attention. However, their luminescent property is still under debate. In this work, we first systematically ...studied the colloidal preparation of Cs4PbX6 NCs. It is found that the critical parameter for the formation of Cs4PbX6 NCs is the ratio between Cs and Pb. Pure Cs4PbX6 NCs are nonluminescent. The luminescence property of previous reported Cs4PbX6 NCs may come from the impurity of luminescent CsPbX3 NCs. No coexistence of both Cs4PbX6 and CsPbX3 phase has been found in one single nanoparticle. The water-triggered transformation from nonluminescent Cs4PbX6 NCs to luminescent CsPbX3 NCs has been quantitatively studied. The potential application of Cs4PbX6 NCs in humidity sensor and anticounterfeiting have been demonstrated. This work is important because it not only confirmed the nonluminescent nature of Cs4PbX6 NCs but also demonstrated the potential application of such NCs.
•P-type characteristic is observed for hot-cast MAPbI3 thin films.•Substrate temperature plays some roles for film stability.•Low trap state density can be obtained from large grain hot-cast MAPbI3 ...films.
Hot-cast CH3NH3PbI3 perovskite thin films are fabricated in ambient air using heated substrates. All the perovskite films prepared are stored in a low-humidity environment. Interestingly, it has been observed that the perovskite films fabricated with high-temperature substrates degrade at a slower rate compared to those prepared at lower temperatures. Even after one week, the morphology of the films remains unchanged when produced with high-temperature substrates under 35–40 % relative humidity (RH). The hot-cast films exhibit p-type characteristics, as evidenced by their surface photovoltage signals. During the aging process, the iodine ions seem to vaporize as evidenced by the reduction of the I/Pb ratios in the energy-dispersive X-ray spectroscopy (EDX) spectra. The hot-cast perovskite films show relatively low surface trap states, ranging from 1015–1016 cm−3, along with low energy band tails of approximately 20 meV.
Perovskites are promising solution processible materials widely used for solar cell application. We developed a vacuum-assisted deposition (VAD), which allowed spin-coating process under different ...vacuum conditions. Via two-step deposition for perovskite solution, VAD affects evaporation rate during deposition and perovskite formation. VAD improved all key properties necessary for optoelectronics like morphology, UV–visible absorption, and crystallinity along with UV, thermal, and moisture stability. Moreover, perovskite films became harder with VAD, paving the way for high mechanical stability. VAD opened a new door for high stability, dense perovskite films and could be adapted for various perovskite compositions for optoelectronic application.
Results of a temperature dependence study of photoinduced charge separation across P3HT nanocrystals at P3HT/ITO interfaces have been investigated by modulated surface photovoltage (SPV) spectroscopy ...in a fixed capacitor arrangement. The SPV measurements were correlated with the crystalline sizes of P3HT nanocrystals determined by grazing incidence X-ray diffraction (GIXRD). The crystalline sizes of P3HT nanocrystals were varied systematically by progressive heating/cooling cycles identical for SPV and GIXRD measurements. Photovoltage signals, indication of photoinduced charge dissociation in space, at the P3HT/ITO interface were collected, and electrons were separated across the first monolayer of P3HT nanocrystals at the P3HT/ITO interface due to band bending. The activation energies for quenching of the in-phase and phase-shifted by 90° SPV signals were 0.7 and 0.6 eV, respectively. Thermal activation of the formation of P3HT nanocrystals was of the same order as the enthalpy of fusion of ideal crystals from regioregular P3HT. A schematic drawing of photoinduced charge separation at the P3HT/ITO is proposed.
(PEA)
(MA)
Pb
I
Br
perovskites are semi-transparent, color-tunable thin films with broader band gaps. They have the potential for semi-transparent solar cell and smart window applications. Solvent ...engineering significantly alters the morphology, absorbance, crystallinity, charge separation, and defects, thereby influencing the optoelectronic properties. Herein, we investigated the effect of the solvent type on the low dimensional, mixed halide perovskite thin films (
= 1, 3, and 5) and identified DMF : DMSO = 8 : 2 as the most suitable solvent. The mixed solvent regulated the growth rate of perovskites, which led to the smooth morphology and larger crystallite size. Through surface photovoltage spectroscopy and time resolved photoluminescence, good charge separation and low defects were linked to DD82 usage.
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•The XRD pattern of a PTB7 film has shifted from 22.3° to 18.6° when the PC71BM is added.•EELS spectra of PTB7 and PC71BM are centered at 22.7eV and 24.5eV, respectively.•The addition ...of the DIO (3%vol) is found to cause a significant improvement in electron mobility in the blend.
Visualizing and controlling the phase separation of the donor and acceptor domains in organic bulk-hetero-junction (BHJ) solar devices made with poly(4,8-bis(2-ethylhexyl)oxybenzo1,2-b:4,5-b’dithiophene-2,6-diyl3-fluoro-2-(2-ethyl-hexyl)carbon-ylthieno3,4-bthiophenediyl) (PTB7) and 6,6-phenyl-C71-butyric acid methyl ester (PC71BM) are needed to achieve high power conversion efficiency (PCE). Traditional bright-field (BF) imaging, especially of polymeric materials, produces images of poor contrast when done at the nanoscale level. Clear nanoscale morphologies of the PTB7:PC71BM blends prepared with different 1,8-diiodooctane (DIO) concentrations were seen when using the energy-filtered transmission electron microscopy (EFTEM). The electron energy loss (EELS) spectra of the pure PTB7 and PC71BM samples are centered at 22.7eV and 24.5eV, respectively. Using the electrons whose energy losses are in the range of 16–30eV, detail information of the phase morphology at the nanoscale was obtained. Correlations between the improvement in the photovoltaic performances and the increased electron mobility were seen. These correlations are discussed in terms of the changes (at the nanoscale level) in blending phase morphology when different DIO concentrations are added.
In solution-processed perovskite semiconductors, ultraviolet (UV) radiation can induce structural degradation in the light-absorbing layer, for instance, methylammonium lead iodide (MAPbI3). In this ...paper, we use modulated surface photovoltage (SPV) spectroscopy to track the mechanisms of photo-generated charge generation and separation as well as the formation of defects in formamidinium lead triiodide (FAPbI3) and cesium (Cs)-containing FAPbI3 (FA x Cs1–x PbI3) perovskite when exposed to different durations of UV-light treatment. The measured SPV signals (in-phase and out-phase (shifted by 90°)) were found to be strongly dependent on the addition of Cs and on the UV exposure times. Upon the partial incorporation of Cs, the improved stability in the structural and optical properties was observed. The formation of the δ-CsPbI3 phase in the FA x Cs1–x PbI3 perovskite is attributed to the stabilization of the FAPbI3/CsPbI3 interface, which would efficiently inhibit the phase segregation and provide for a stable medium for the modulated charge separation under UV illumination.
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