CH3NH3PbI3 Perovskite Thin Films Research Articles

Exploring the impact of antimony trisulfide (Sb2S3) doping on the optoelectronic functionality of hybrid CH3NH3PbI3 perovskite layers and solar cells

In this study, we present the effect of doping with antimony trisulfide (Sb2S3) nanobare on the electrical, optical, structural, and morpholigcal properties of CH3NH3 PbI3 perovskite thin films. Doped with Sb2S3 nanobare, the thin coatings demonstrated an exceptionally high degree of purity, featuring a tetragonal phase within its single-phase structure. This allowed for the creation of (110) textured CH3NH3PbI3 films, which comprised micrometer-sized grains arranged in a vertical direction across the entire film thickness and featured high crystallinity. Additionally, the CH3NH3PbI3 perovskites films exhibited significant optical absorption at appropriate energy levels and exhibited a high gachin rate of photons. Substance doping methods that can optimize the morphology of the perovskite active layer with large granules are exceedingly desirable in order to reduce charge carrier recombination. The synthesis of perovskite films with dimensions on the order of microns can be achieved by incorporating a regulated quantity of Sb2S3 nanobare into the precursor solution. The incorporation of these textured CH3NH3PbI3:Sb2S3 nanobare films significantly enhanced the power conversion efficiency (PCE) of the perovskite solar cells. The solar cell device configuration utilized in this investigation is as follows: glass/FTO/TiO2/CH3NH3PbI3:Sb2S3 nanobars/spiro-OMeTAD/Au. By employing Sb2S3 nanobars at a concentration of 9 mg/mL, we successfully attained an exceptional power conversion efficiency of 15.87 %. The resulting values for these parameters include an open-circuit voltage VOC of 1.09 V, a short-circuit current density JSC of 21.15 mA/cm2, and a fill factor FF of 68.87 %.

Efficient methylammonium lead triiodide CH3NH3PbI3 perovskite solar cells with improved surface properties using PM6 (PBDB-T-2F) polymer

Polymer additives are extensively used and serve a crucial role in the advancement of CH3NH3PbI3 perovskite photovoltages. This work demonstrates the effect of Poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2-b:4,5-b’]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c’]dithiophene-4,8-dione)PBDB-T-2F (PM6) at various concentrations on the crystallinity, surface structure, optical and electrical properties of CH3NH3PbI3 perovskite thin films. Polymer molecules are utilized to promote the growth of crystal particles in the active layer. The chemical reaction between their functional groups and theperovskite absorber and transportation layers leads to defect passivation and improved device efficiency. The results show that the absorption spectra of CH3NH3PbI3:PM6 perovskite thin films cover the extensive absorption spectra in the UV and visible light range between 500 and 800 nm, indicating that CH3NH3PbI3:PM6 perovskite is an effective visible light absorber. The PL intensity decreased as the polymer PM6 concentration increased up to 6 mg/ml, then increased when the concentration of PM6 was raised to 8 mg/ml. Quenching the sample with 6 mg/mL of PM6 caused rapid electron transfer to the substrate. According to surface morphology findings, the perovskite film's irregularity was reduced from 37.05 nm for pure thin film to 12.27 nm when added 6 mg/ml of PM6. The 6 mg/mL PM6 film exhibited the most uniformity and fluidity. The surface of the perovskite film was transformed into smooth, compacted pores with a particle size of 2 µm, which could facilitate charge transport for enhanced photovoltaic performance. The solar cell devices had a PCE of 14.68 %, a short-circuit current density of 19.32 mA/cm2, an open circuit voltage of 1.20 V, and a fill factor of 63.35 %.

Ellipsometric studies of CH3NH3PbI3 perovskite thin film on different underlayers and its effect on photovoltaic device performance

Measurement of optical constants of semiconducting thin films is an ongoing strive for optoelectronics and related applications. The optical constants (refractive index (n) and extinction coefficient (k)) plays a vital role in optimizing the thicknesses of different layers for improved performance in optoelectronic devices such as solar cells, photodetectors, light-emitting diodes, etc. In the present work, we measured the optical constants of methylammonium lead iodide (CH3NH3PbI3 or MAPbI3) deposited on five different underlying layers/substrates and estimated the error in simulated current density estimation for a device with the architecture of Glass/ITO/TiO2/CH3NH3PbI3/Spiro-OMeTAD/Au. The optical modeling and performance analysis of this device has been done using transfer matrix method while spectroscopic ellipsometry has been used to measure the optical constants of MAPbI3 film on five different types of underlayer stacks. A maximum error of around 10.6% has been observed when the optical constants are taken from MAPbI3 films deposited on the different underlying stacks. Additionally, experimental aspects of these films such as surface morphology, structural, and optical properties have also been studied to better understand and correlate the observed differences.

Anomalous p-type characteristic and recrystallization upon aging of hot-cast CH3NH3PbI3 perovskite thin films grown under atmospheric air

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.

Improved performance and stability in CH3NH3PbI3/Si heterojunction photodetectors realized by ZIF-67 additive assisted Co ion doping

Lead halide perovskites have been regarded as promising materials for fabrication of high-performance photodetectors (PDs). However, spin-coated perovskite thin films generally have suffered from high-density grain boundaries and defect states, which severely deteriorated the performance and stability of resulting PDs. Fortunately, the above issues can be effectively solved via additive assisted metal ions doping. In this work, Co-based zeolite imidazole framework (ZIF-67) additive assisted Co ion doping has been proposed to prepare high-quality perovskite CH3NH3PbI3 (MAPbI3) thin films. Morphological, structural, optical, and electrical studies have shown that Co ion doping decreased grain boundaries as well as suppressed defect states, which greatly enhanced the performance and stability of MAPbI3/Si heterojunction PDs, including reducing dark current, increasing photocurrent, and increasing response speed. Finally, the mechanisms of suppression of defect states benefiting from Co ion doping were discussed based on density functional theory calculations. The results provided in this work will pave the way for development of high-performance and stable MAPbI3 PDs in the future.

Experimental and theoretical investigations on fullerene (C60) induced compact CH3NH3PbI3 perovskite thin films

In the present work, pure and Fullerene (C60)-doped methyl ammonium lead halide (CH3NH3PbI3) perovskite thin films were prepared on glass substrates by spin coating method at different concentrations of fullerene (C60).The structural, morphological, and optical characteristics of as-prepared thin films were analysed using experimental and computational methods. The X-ray diffraction studies and their Reitveld refinement analysis of the samples confirms that all deposited perovskite thin films have tetragonal structure and are highly oriented along the (110) plane. The morphology of the perovskite films was investigated by field emission scanning electron microscope (FE-SEM). The elemental composition of perovskite thin films was confirmed by Energy Dispersive X-rays Analysis (EDAX). The addition of fullerene (C60) resulted in the increase of grain size sand a more compact surface development of the perovskite thin films with fewer flaws as compared with perovskite thin films without (C60) was evaluated. Also, geometrical, electronic and optical properties were studied by using the first principles DFT computational method. Optical properties have been studied experimentally and verified computationally. All the perovskite thin film samples exhibit direct band-gap which is suitable for solar cells applications.

Preparation of MAPbI3 perovskite film by pulsed laser deposition for high-performance silicon-based heterojunction photodetector

This study investigates the preparation and characterization of CH3NH3PbI3 (MAPbI3) perovskite thin films. The films were prepared using a one-step pulsed laser deposition technique at different laser fluences. Structural, optical, and electrical properties of CH3NH3PbI3 films were investigated at various laser fluences. The X-ray diffraction (XRD) studies confirm the formation of β-MAPbI3 films. The optical energy gap of MAPbI3 perovskite film was calculated and is found to be in the range of 1.53–1.68 eV. Scanning electron microscope (SEM) analysis reveals the formation of rod-like and platelet morphologies, while energy dispersive X-ray spectroscopy analysis reveals that the [I]/[Pb] ratio of the films prepared with 2, 2.5, and 3 J/cm2 was 1.3, 2.3, and 1.36, respectively. Hall effect results confirm that the MPPbI3 films are p-type and the mobility of MAPbI3 film decreases from 0.26 to 0.084 cm2V−1s−1 as laser fluence increases from 2 to 3 J/cm2. The optoelectronic characteristics of the p-MAPbI3/n-Si photodetector were investigated as a function of laser fluence. By selecting an optimum laser fluence, a maximum responsivity of 2.57 A/W and an external quantum efficiency of 7.08 × 102% at 450 nm were obtained. The energy band lineup of the p-MAPbI3/n-Si photodetector fabricated with 2.5 J/cm2 was constructed.

Effect of cesium doping and antisolvent on the linear and nonlinear characteristics of CH3NH3PbI3 perovskite thin films

Effect of cesium doping and antisolvent on the linear and nonlinear characteristics of CH3NH3PbI3 perovskite thin films

A simple, low-cost modified drop-casting method to develop high-quality CH3NH3PbI3 perovskite thin films

To make perovskite solar cells competitive and efficient, it is necessary to control the crystallinity along with full coverage of the used substrate. Nowadays, numerous techniques have applied to improve and control the crystallinity of fabricated perovskite films, but still, have the most critical issue for perceiving high-performance perovskite solar cells. Herein, a low-cost yet effective procedure has used to fabricate thin-films of methylamine lead halide (CH3NH3PbI3) perovskite semiconductor. Uniform and high-quality CH3NH3PbI3 perovskite thin films were successfully fabricated on a glass substrate using a modified drop-casting method. Morphological characterization has shown an extremely compact, highly crystalline, and dense microstructure pinhole-free thin-film without any impure phase. Compared to the spin coating method, thin-films processed have been exposed to retain an enhanced film quality with higher crystallinity. Furthermore, a voltage-current characteristic has shown that the photoconductivity significantly enhanced the films processed with this versatile method. These results were also validated by absorbance and photoluminescence measurements. Achieved results highlight the significance of this low-cost method for forthcoming high-performance photovoltaic devices based on CH3NH3PbI3 semiconductor thin films.

Mesoporous TiO2 electron transport layer engineering for efficient inorganic-organic hybrid perovskite solar cells using hydrochloric acid treatment

We demonstrated effects of wet chemical processes using hydrochloric on crystallite structures, optical and electronic properties, and surface morphology of TiO2 thin films and enhancement in photovoltaic performance of perovskite solar cell using HCl-treated mesoporous TiO2 electron transport layers (ETLs). By treating mesoporous TiO2 thin films with HCl, hydroxyl groups on the surface were chemically neutralized and the film porosity was enhanced. Furthermore, the crystallite structure analyses indicated that CH3NH3PbI3 perovskite thin films deposited on the HCl-treated compact and mesoporous TiO2 ETLs possessed the relatively high crystallization along with avoiding formation of unexpected PbI2 crystals. As a result, the best power conversion efficiencies of devices using the HCl-treated mesoporous TiO2 ETLs were improved to 18.4% under forward bias scans.

Solid-state reaction process for high-quality organometallic halide perovskite thin film

Recently, a hybrid perovskite material, ABX3 (A= Cs, CH3NH3, NH2CHNH2; B= Pb, Sn; X= Cl, Br, I), has received much attention as an active layer in new-generation solar cells. This material is usually fabricated with either a one-step or a two step process in solution. However, the surface morphology, nucleation rate and grain growth rate of the CH3NH3PbI3 perovskite light absorber prepared by the solution reaction process (SRP) are hard to control. Here, we show a fast solid-solid reaction process (SSRP), to fabricate ultraflat (roughness of approximately 12 nm) CH3NH3PbI3 perovskite thin films with large grain sizes (~947 nm). The SSRP simply involves directly contacting a lead iodide thin film (PbI2) with methylammonium iodide powder (CH3NH3I) without any chemical reagents at 120°C under a normal atmospheric environment. The SSRP reaction dynamics is investigated by an in situ heating scanning electron microscope (SEM) system. This innovative SSRP is an easy approach for the large-scale fabrication of planar heterojunction perovskite solar cells and allows us to demonstrate a power conversion efficiency of approximately 15.27% (active area of 0.16 cm2).

Small grains as recombination hot spots in perovskite solar cells

Summary Non-radiative recombination in the perovskite bulk and at its interfaces prohibits the photovoltaic performance from reaching the Shockley-Queisser limit. While interfacial recombination has been widely discussed and demonstrated, bulk recombination and especially the influence of grain boundaries remain under debate. Most studies explore the role of grain boundaries on perovskite films rather than devices, making it difficult to link the film properties with those of the devices. Here, we systematically investigate the effects of grain boundaries on the performance of perovskite solar cells by two different methods. By combining experimental characterization with theoretical device simulations, we find that the recombination at grain boundaries is diffusion limited and hence is inversely proportional to the grain area to the power of 3/2. Consequently, the prevalence of small grains—which act as recombination hot spots—across the perovskite active layer dictates the photovoltaic performance of the perovskite solar cells.

Effect of film structure on CH3NH3PbI3 perovskite thin films’ degradation

The instability of CH3NH3PbI3 perovskite hybrid organic–inorganic films is a serious problem, which might be a drawback for their use in solar energy conversion. In this work, we have evaluated the degradation of the perovskite films and studied the influence of film morphology on their degradation. CH3NH3PbI3 perovskite thin films were deposited on glass substrates by a spin coating technique at different centrifugation speeds using different solvents. This study aims to determine the films’ properties that may control the degradation process. This study was based on the comparison between the characteristics determined from XRD analysis and optical transmittance of freshly deposited films and those aged 1 year in ambient air at room temperature and dark conditions. The degradation was manifested by the partial decomposition of the perovskite to PbI2, I2, and metallic lead. The degradation evaluation was achieved by the determination of the variation of the most intense XRD diffraction peak in the freshly prepared film and after aging. The results indicated that the degradation is very sensitive to the films’ porosity and thickness. Reducing the thickness of the film or increasing the porosity enhances the degradation process.

Effect of additive polarity on the stability of organic-inorganic hybrid CH3NH3PbI3 perovskite thin film

Synthesis of organic-inorganic hybrid CH3NH3PbI3 perovskite thin film from Pb(NO3)2 precursor was carried out by using alcohol with various polarity (isopropanol, 1-butanol and 1-propanol) as the additive. Preparation of CH3NH3PbI3 perovskite thin film was conducted by firstly forming Pb(NO3)2 thin film as the film’s precursor using spin coating method at 2500 rpm for 30 s with DMSO as the main solvent and isopropanol, 1-butanol or 1-propanol as the solvent additives. Pb(NO3)2 thin film was immersed in methyl ammonium iodide solution for 30 min to produce CH3NH3PbI3 perovskite thin film. The effect of solvent additive polarity on the grain size of perovskite film was studied using electron microscope method. Stability of CH3NH3PbI3 perovskite thin film was studied by using XRD and SEM. The result showed that increasing polarity of the solvent additives resulted in decreasing on the crystallinity of Pb(NO3)2 thin film. Pb(NO3)2 thin film with low crystallinity yielded high purity of CH3NH3PbI3 perovskite thin film with grain size up to 2.45 μm and have good stability with 43.09% degradation percentage for 24 h.

Influence of Deposition and Annealing Parameters on the Degradation of Spray-Deposited Perovskite Films

Abstract In this work, CH3NH3PbI3 perovskite thin films were deposited by the spray-coating method in ambient conditions using different deposition temperatures and annealing times. They were then exposed to high humidity in order to investigate the relation between processing parameters and degradation mechanisms. FTIR and XRD analyses identified two degradation mechanisms, one reversible, the formation of monohydrated perovskite, CH3NH3PbI3∙H2O, and another irreversible, the decomposition of perovskite into PbI2 and CH3NH3I. It was found that perovskite degradation is very sensitive to deposition parameters and that long annealing times at high temperatures increase compound stability, retarding reversible degradation even after a long exposure to ambient conditions. This is attributed to the formation of a small amount of PbI2 during deposition that acts as a protective layer against moisture, preventing the formation of monohydrated perovskite. Additionally, no signs of dihydrated perovskite were found in the films even after 50 days of exposure to high humidity.

Determination of residual dimethyl sulfoxide by high-resolution continuum source graphite furnace molecular absorption spectrometry

High-resolution continuum source molecular absorption spectrometry (HR-CSMAS) has been extended to the determination of sulfur-containing organic molecule, on the example of dimethyl sulfoxide (DMSO) as a residual solvent in CH3NH3PbI3 perovskite thin films. For this purpose, DMSO molecules were converted into CS molecules by pyrolysis in a graphite furnace at low temperature and the sulfur content was determined by measuring molecular absorption of CS at 258.055 nm. An aqueous solution of DMSO was used for calibration. A characteristic mass of 17 ng was achieved for S after pyrolysis at 160 °C by using Pd as a chemical modifier. Furthermore, the content of DMSO was normalized to that of Pb whereas the content of Pb was determined by reducing the Pb in the perovskite to metallic Pb with Zn powder and measuring absorption of the weak Pb line at 261.418 nm by high-resolution continuum source atomic absorption spectrometry (HR-CSAAS). The Pb content remained constant whereas the S/Pb molar ratio decreased with increasing annealing time. Our results open new opportunities for the characterization of residual DMSO in wide classes of materials.

Anti-solvent mixture-mediated reduction of photocurrent hysteresis in high-impurity perovskite precursor based MAPbI3 solar cells

High-impurity precursor based CH3NH3PbI3 (MAPbI3) perovskite thin films are fabricated by using the one-step spin-coating method with an anti-solvent mixture-mediated nucleation (ASMEN) process under various dropping times. The structural, optical and excitonic properties of the resultant perovskite thin films are characterized through the X-ray diffractometer, absorbance spectrometer, photoluminescence spectrometer and Raman scattering spectrometer. The experimental results show that the dropping time and the use of 10% dicloromethane (DCM) in the ASMEN process strongly influences the formation of point defects in the resultant MAPbI3 thin film, which dominates the current-hysteresis behavior in the current density-voltage curves of solar cells. In addition, this investigation helps further understand the effects of toluene/DCM anti-solvent mixture on the formation of point defect-free MAPbI3 thin films.

One-step method for the fabrication of high-quality perovskite thin-films under ambient conditions: Stability, morphological, optical, and electrical evaluation

Stability is still a property that limits the commercialization of perovskite solar cells. Thus, with the development of continuous deposition methods, it is essential to determine their feasibility in terms of stability, and not only on the efficiency of the devices produced. In this work, a hot air blow-drying (HABD) method is proposed as an alternative for the deposition of CH3NH3PbI3 (MAPbI) perovskite thin-films. The ability of HABD to produce homogeneous and stable thin-films was systematically studied and compared with those produced with air at standard conditions (25 °C, 25% relative humidity). The MAPbI thin-films were characterized by infrared spectroscopy and X-ray diffraction revealing that air temperature rules the film hydration. Partial degradation after using air at standard conditions was observed in contrast with the stable and pure perovskite phase obtained when using air heated at 90 C°. The influence of solution concentration on the surface coverage was determined by scanning electron and atomic force microscopies. It was found that 4 µL of precursors solution (0.434 M) produced a homogeneous MAPbI thin-film with ~180 nm thickness and roughness of (Rq ~ 29 nm) covering a 6.25 cm2 area. Moreover, the outstanding optical and electrical properties of MAPbI were not affected by the deposition procedure. Remarkably, degradation tests demonstrate that our HABD method is capable of producing stable MAPbI thin-films with excellent resistance to degradation at ambient conditions (up to 15 days), which makes it a promising low-cost and easy to use method for the continuous fabrication of perovskite solar cells.

Highly Conductive P-Type MAPbI3 Films and Crystals via Sodium Doping.

To regulate the optical and electrical properties of the crystals and films of the intrinsic methylammonium lead iodide (CH3NH3PbI3), we dope them with sodium (Na) by selecting sodium iodide (NaI) as a dopant source. The highly conductive p-type sodium-doped CH3NH3PbI3 (MAPbI3: Na) perovskite single crystals and thin films are successfully grown using the inverse temperature crystallization (ITC) method and antisolvent spin-coating (ASC) method, respectively. With the increase of Na+ doping concentration, the grain size of the film increases, the surface becomes smoother, and the crystallinity improves. Hall effect results demonstrate that both the MAPbI3: Na thin films and single crystals change their quasi-insulating intrinsic conductivity to a highly conductive p-type conductivity. The room-temperature photoluminescence (PL) peaks of doped MAPbI3 films slightly blue shift, while the photocarriers' lifetime becomes longer. The optical fingerprints of the doped levels in MAPbI3: Na perovskites can be identified by temperature-dependent PL. Obvious fingerprints of Na-related acceptor (A0X) levels in the doped MAPbI3: Na were observed at 10 K. These results suggest that sodium doping is an effective way to grow highly conductive p-type MAPbI3 perovskites.

Effect of acetic acid concentration on optical properties of lead acetate based methylammonium lead iodide perovskite thin film

Abstract High absorption of perovskite thin films is crucial for efficient metal halide perovskite solar cells. In this study, methylammonium lead iodide (CH3NH3PbI3) perovskite thin films are prepared using lead (II) acetate Pb(Ac)2, acetic acid (HAc) and CH3NH3I through solution method. The effect of HAc volume (0 ml–100 ml at step size of 25 ml HAc) on optical properties and parameters of the CH3NH3PbI3 perovskite thin films developed are investigated using UV–Vis spectrophotometry and mathematical correlations. Interestingly, the increase of HAc amount to 75 ml leads to an increase in absorbance, refractive index, extinction co-efficient, dielectric properties and optical conductivity and a decrease in transmittance and optical band gaps of the CH3NH3PbI3 perovskite thin films. The optimized film is obtained at 75 ml HAc at which refractive index, film thickness and optical band gap is 1.45 at 485 nm, 355 nm and 1.47 eV, respectively. The enhanced absorption of the optimized thin film is attributable to an increase in structure ordering at HAc amount equals 75 ml. The fabricated CH3NH3PbI3 perovskite thin films have potential as ideal antireflection coatings for solar cells and optoelectronic applications.