Synthesis of Hybrid Lead Iodide Perovskite Thin Film by Two-Step Method Modified with a Double Dipping Circle to Control Its Crystallization and Morphology to Improve Solar Cells’ Performance (original) (raw)
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Advances in Materials Science and Engineering, 2016
We present a critical review of the effects of processing conditions on the morphology of methylammonium lead iodide (CH3NH3PbI3) perovskite solar cells. Though difficult to decouple from synthetic and film formation effects, a single morphological feature, specifically grain size, has been evidently linked to the photovoltaic performance of this class of solar cells. Herein, we discuss experimental aspects of optimizing the (a) temperature and time of annealing, (b) spin-coating parameters, and (c) solution temperature of methylammonium iodide (MAI) solution.
Physical chemistry chemical physics : PCCP, 2016
Lead halide based perovskite solar cells are presently the flagship among the third generation solution-processed photovoltaic technologies. The organic cation part in the perovskite plays an important role in terms of crystal structure tuning from tetragonal to trigonal or pseudocubic or vice versa depending on the organic cations used, while it also displays different microstructure. In this paper, we demonstrate the influence of the organic cation part with respect to optical properties, hysteresis behavior, and stability. This study offers a clear understanding of the perovskite properties and how they can be modulated by compositional engineering. With a rational choice, light harvesting abilities and hysteresis behavior can be controlled in these systems. The substitution of formamidinium cation by methylammonium cation allows achieving low temperature annealing and inducing stability in perovskites together with enhanced photovoltaic properties. By the use of in-situ scanning...
Effect of different lead precursors on perovskite solar cell performance and stability
J. Mater. Chem. A, 2015
We present the use of halide (PbCl 2 ) and non-halide lead precursors (Pb(OAc) 2 (OAc=CH 3 CH 2 COO -), Pb(NO 3 ) 2 , Pb(acac) 2 (acac=(CH 3 COCHCOCH 3 ) -) and PbCO 3 ) for the preparation of perovskite solar cells. We have confirmed by X-ray diffraction the growth of CH 3 NH 3 PbI 3 in all the analyzed cases, except for PbCO 3 , independently of the lead precursor used for the synthesis of the perovskite. In addition, different cell configurations, thin film and mesoporous scaffolds, TiO 2 or Al 2 O 3 , have also been prepared. We have observed that the lead precursor influences strongly on the structural properties of perovskite (grain size), as well as on the solar cell performance. Photovoltaic conversion efficiencies comparable to those achieved when using the commonly employed PbCl 2 have been obtained with Pb(OAc) 2 as lead source. Stability studies of the perovskite films and devices have also been carried out; demonstrating that the lead precursor also influences this aspect. Stability is strongly affected by atmosphere and illumination conditions, but also by the lead precursor employed for the perovskite synthesis. These results highlight that other lead sources, different to the commonly used PbCl 2 and PbI 2 , are also suitable for the development of PSCs, opening a new way for device performance optimization.
Solar Energy, 2021
The study aimed to investigate the role of the metal-organic frameworks in the perovskite solution, and their effects on perovskite crystal, absorption, film formation, and device performance. Three supramolecular compounds of Zirconium(IV), Indium(III) and Zinc(II) with proton transfer compound, obtained from 2,6-pyridinedicarboxylic acid and 2,6-pyridinediamine, were synthesized, and characterized and used as additives in perovskite solar cells. The additives with different amounts were added to the CH 3 NH 3 PbI 3 solutions to control the morphology of the perovskite layer during the film formation process. More importantly, the metal-organic frameworks serving as additives can help to form a better perovskite layer with fewer voids between CH 3 NH 3 PbI 3 domains during phase transformation. The findings showed that using a 2 wt% of zinc metal-organic framework in the perovskite layer achieved yields results in the performance of perovskite solar cells. As a result, the current density (Jsc) of the new device increased from 7.02 to 9.36 mA/cm 2 , and the Fill-Factor (FF) of the device improved from 0.42 to 0.62 for 2 wt% of zinc metal-organic framework. Also, the PCE (Efficiency) of perovskite solar cells achieved more than 90% of improvement after adding 2 wt% of zinc metal-organic framework as an additive in HTM-free conditions. FE-SEM and XRD studied the morphology of this new perovskite layer.
Scientific Reports, 2016
In CH3NH3PbI3-based high efficiency perovskite solar cells (PSCs), tiny amount of PbI2 impurity was often found with the perovskite crystal. However, for two-step solution process-based perovskite films, most of findings have been based on the films having different morphologies between with and without PbI2. This was mainly due to the inferior morphology of pure perovskite film without PbI2, inevitably produced when the remaining PbI2 forced to be converted to perovskite, so advantages of pure perovskite photoactive layer without PbI2 impurity have been overlooked. In this work, we designed a printing-based two-step process, which could not only generate pure perovskite crystal without PbI2, but also provide uniform and full surface coverage perovskite film, of which nanoscale morphology was comparable to that prepared by conventional two-step solution process having residual PbI2. Our results showed that, in two-step solution process-based PSC, pure perovskite had better photon ab...
Solar RRL - Wiley, 2023
The presence of residual lead iodide phase in perovskite films, inherent to the two-step spin-coating method, has been reported to be beneficial for the per- formance of perovskite solar cells (PSCs); however, it may potentially undermine the photostability of PSCs. Herein, four distinct sets of perovskite films and devices are fabricated via the two-step spin-coating process, each under different processing conditions. All conditions demonstrate promising power conversion efficiency in PSCs. However, the aspect of photostability is found to be signif- icantly influenced by unreacted PbI2 in the perovskite films. Varying degrees of residual PbI2 are detected among these films. Upon light exposure, it is observed that residual PbI2 within perovskites undergoes decomposition into metallic lead (Pb0) and mobile iodine, and these can affect the photovoltaic performance of the PSCs. The presence of mobile ions in metal–halide perovskites has generated substantial concern due to their impact on hysteresis within the J–V curve. Furthermore, the metallic lead (Pb0) containing perovskite films exhibits a prominent inverted hysteresis in the J–V curve
In CH 3 NH 3 PbI 3-based high efficiency perovskite solar cells (PSCs), tiny amount of PbI 2 impurity was often found with the perovskite crystal. However, for two-step solution process-based perovskite films, most of findings have been based on the films having different morphologies between with and without PbI 2. This was mainly due to the inferior morphology of pure perovskite film without PbI 2 , inevitably produced when the remaining PbI 2 forced to be converted to perovskite, so advantages of pure perovskite photoactive layer without PbI 2 impurity have been overlooked. In this work, we designed a printing-based two-step process, which could not only generate pure perovskite crystal without PbI 2 , but also provide uniform and full surface coverage perovskite film, of which nanoscale morphology was comparable to that prepared by conventional two-step solution process having residual PbI 2. Our results showed that, in two-step solution process-based PSC, pure perovskite had better photon absorption and longer carrier lifetime, leading to superior photocurrent generation with higher power conversion efficiency. Furthermore, this process was further applicable to prepare mixed phase pure perovskite crystal without PbI 2 impurity, and we showed that the additional merits such as extended absorption to longer wavelength, increased carrier lifetime and reduced carrier recombination could be secured. Recently, organometal trihalide perovskite materials having composition ABX 3 (e.g. A = Cs + , CH 3 NH 3 + (meth-ylammonium, MA), or HC(NH 2) 2 + (formamidinium, FA); B = Pb or Sn; X = I, Br or Cl) have been investigated extensively for use as light-absorbing material in solar cells because of their unique properties such as direct optical bandgap, broadband light absorption, bipolar transport, and long carrier diffusion length. Since the first report about perovskite solar cells (PSC) having 3.81% power conversion efficiency (PCE) by Kojima et al. in ref. 1, which triggered intensive research in the development of PSC, remarkable enhancement in power conversion efficiency (PCE) reaching 20% has been achieved during past several years 2–4. In conventional silicon-based p-n junction photovoltaic (PV) devices, the pure crystal structure in photoac-tive layer has been known to be advantageous to efficient charge transport and reduced exciton quenching for high efficiency solar cell. However, in MAPbI 3-based PSC showing high efficiency, tiny amount of residual PbI 2 impurity was often found with the perovskite crystal phase, even though the equimolar composition of organic (MAI) and inorganic (PbI 2) components was utilized to fully convert them to perovskite crystal 3,5–14. Therefore, various approaches have been reported to find out if perovskite crystal with PbI 2 impurity would be advantageous to the performance of PSC or not. However, in general, the crystalline structure and nanoscale morphology of perovskite photoactive layers are significantly influenced by their deposition methodology 15–22 , and therefore those reports should be individually interpreted depending on their growth mechanism. Chen el al. reported an approach to produce pure MAPbI 3 film by treating as-deposited PbI 2 film with MAI vapor for several hours, from which PbI 2 component could be reversibly regenerated when annealed at 150 °C 5,6. They showed that the regenerated PbI 2 from the pure MAPbI 3 crystal structure by annealing was helpful to pas-sivate grain boundary (GB) between crystal domains, consequently improving their device performances due to the reduced recombination 6. Similarly, Zhang et al. investigated the role of PbI 2 in their perovskite film, grown by spin-casting hydrohalide deficient PbI 2 ·xHI (x = 0.9~1) precursor under MA vapor atmosphere. Using their
Scientific Reports
Organic–inorganic hybrid perovskite is the most promising active layer for new generation of solar cells. Despite of highly efficient perovskite active layer conventionally fabricated by spin coating methods, the need for using toxic solvents like dimethylformamide (DMF) required for dissolving low soluble metal precursors as well as the difficulties for upscaling the process have restricted their practical development. To deal with these shortcomings, in this work, lead sulphide as the lead metal precursor was produced by aqueous chemical bath deposition. Subsequently, PbS films were chemically converted to PbI2 and finally to mixed-cation mixed halide perovskite films. The microstructural, optical and solar cell performance of mixed cation mixed halide perovskite films were examined. Results show that controlling the morphology of PbI2 platelets achieved from PbS precursor films enabled efficient conversion to final perovskite films. Using this processing technique, smooth and pin...