Sharif Digital Repository

The present research sheds new light on the development of a triple-cation quasi-two-dimensional (2D) perovskite family with the general formula of (S1−xS′x)2[Cs0.05(FA1−xMAx)0.95]3Pb4(I1−xBrx)13, in which two spacers, namely 5-ammonium valeric acid iodide (S) and tetra-n-octylammonium bromide (S′) were simultaneously incorporated. Morphology, crystal structure, optical properties, photovoltaic performance, and internal resistances of such compound were systemically studied in comparison with an analogous single-cation 2D counterpart (i.e. (S)2(FA)3Pb4I13) as a reference. X-ray diffraction set forth that the films deposited based upon these compounds had a 2D perovskite crystal structure... 

In planar perovskite solar cells (PSCs), engineering the extraction and recombination of electron–hole pairs by modification of the electron transport layer (ETL)/perovskite interface is very vital for obtaining high performance. The main idea here is to improve properties of the TiO2/perovskite interface by inserting an ultra-thin layer (UTL) of WO3 or SnO2 with the thickness of less than 10 nm by RF magnetron sputtering method. The structural and electrical characteristics of the samples were tested by XRD, AFM, FE-SEM, Mott-Schottky analysis, UV–Vis spectroscopy, J-V characterization and electrochemical impedance spectroscopy (EIS). It was found that the bilayer structured ETLs exhibit... 

Vacuum deposition of transporting layers, especially the hole-transporting layer (HTL), is still a big challenge for the fabrication of large-area perovskite solar cells (PSCs). In this work, efficient and large-area PSCs are fabricated by thermal evaporation of all the layers. Poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine) (PTAA) is used as the HTL, and a compact layer of PTAA with low thickness (2–10 nm) is successfully deposited using thermal evaporation. The optical and ultraviolet photoelectron spectroscopy (UPS) measurements prove that the evaporated PTAA has a great match with the single A-cation methylammonium triiodide perovskite film in terms of quenching effect and band... 

Perovskite solar cells suffer from various instabilities on all time scales. Some of them are driven by light, in particular when employing compounds with mixed halides. Such light soaking effects have been observed to result in performance changes of solar-cell devices. They have also been spectroscopically investigated in detail on films, where the formation of a low-gap iodine-rich phase, seen as a red shift of the PL, has been found to be responsible for a reduced open-circuit voltage. However, studies synchronously examining device performance and its relation to spectroscopy data are scarce. Here, we perform an in operando study, where we investigate the changes of open-circuit voltage... 

Different polymers have been already introduced for passivating the interfacial defects at the interface of perovskite and the organic hole transport material, meanwhile as an environmental barrier in perovskite solar cells (PSCs). Herein, polyvinylcarbazole (PVK) compared to polymethylmethacrylate (PMMA) at the interface of the perovskite (Cs0.05(MA0.83FA0.17)0.95Pb(Br0.17I0.83)3) layer and CuInS2/carbon as a low-cost inorganic hole-collecting electrode are investigated. By suppressing interfacial recombination using PMMA and PVK, saturation current density (in dark current) decreases one order of magnitude from 7.9 × 10−10 to 4.0 × 10−11 mA cm−2 by adding PMMA and two orders of magnitude... 

In this work, synthesis of CuIn0.75Ga0.25S2 (CIGS) nanoparticles, the formation of stable dispersion, deposition of high-quality films and, fabrication of thin-film Perovskite solar cells are reported. The stability of nanoparticle ink is crucial in the formation of device-quality films. The chalcogenide-based materials are widely used in thin-film solar cells; in particular, Cu(In,Ga)S2 are used as an absorber and hole transporting layer. In the present study, the nanoparticles of about 20 nm size and bandgap of 1.5 eV are synthesized using a heat-up method. A variety of solvents are used as dispersing media and the stability of the inks is evaluated by precise optical monitoring. We... 

One of the key parts of perovskite solar cells which has great influence on their performance and stability is hole transporting layer. Spiro-OMeTAD is extensively used as organic hole transporting material in perovskite solar cells. However, Spiro-OMeTAD is expensive and has low chemical stability. In this study, the solution processed Sb2S3 and Cu3SbS4 nanocrystals have been synthesized and then the n-i-p mesoscopic perovskite solar cells have been fabricated using Spiro-OMeTAD, Sb2S3 and Cu3SbS4 nanocrystals as hole transporting layer at ambient air condition. It is shown that the conduction and valence band levels of the synthesized Sb2S3 and Cu3SbS4 nanocrystals are in the proper... 

A key direction toward managing extrinsic instabilities in perovskite solar cells (PSCs) is encapsulation. Thus, a suitable sealing layer is required for an efficient device encapsulation, preventing moisture and oxygen ingression into the perovskite layer. In this work, a solution-based, low-cost, and commercially available bilayer structure of poly(methyl methacrylate)/styrene-butadiene (PMMA/SB) is investigated for PSCs encapsulation. Encapsulated devices retained 80% of the initial power conversion efficiency (PCE) at 85 °C temperature and 85% relative humidity after 100 h, while reference devices without SB (only PMMA) suffer from rapid and intense degradation after only 2 h, under the... 

A key direction toward enhancing the long term and outdoor stability of the perovskite solar cells is encapsulation. As a result, a suitable encapsulation package is required to prevent moisture and oxygen penetration toward the perovskite solar cells. In this work, a low-cost commercially available bilayer structure of poly (methyl methacrylate)/ room-temperature vulcanizing silicone rubber (RTV) encapsulation package for enhancing the long term stability of the perovskite solar cells has been investigated. Encapsulated cells retained more than 80% of the initial efficiency at the environmental condition of 50% moisture, and room temperature after 1000 h, however reference cell efficiency... 

Organic-inorganic hybrid halide perovskite materials have been most attractive for wide range of optoelectronic applications. Investigating the photo-response in these devices will be very useful to understanding cell performance in different conditions and applications. For understanding non-linearity photo-response we use the Bathocuproine (BCP) as blocking layer in two interfaces of inverted perovskite solar cell (FTO/NiO/BCP/Perovskite/PCBM/Au and FTO/NiO/Perovskite/PCBM/BCP/Au). Employing thick BCP layer (≈15 nm) caused s-shaped JV curve due to charge accumulation at interfaces. The nonlinearity effect was also explored for devices with s-shaped JV and established that device parameters... 

This study represents the investigation of In2S3 thin films, which have been deposited with different Indium salts (Chloride, Acetate, and Nitrate) using the Chemical Spray Pyrolysis (CSP) method. The Mott-Schottky analysis has been used in case of studying the electrical properties of films such as conduction and valence band, carrier densities, Fermi level (Efn), flat band potential, and semiconductor type. In the next step, the Rb1MAFA perovskite solar cell has been simulated, and the results have been validated by the experimental data (with the least parameters for fitting). Finally, In2S3 layers have been inserted on the SnO2 layer to decrease the recombination rate and enhance the... 

Herein, we demonstrate a new fabrication strategy for low-cost and stable-operation perovskite solar cells (PSCs) suitable for commercialization. This is performed by fabrication of the device under ambient conditions using a Cs0.05(MA0.17FA0.83)0.95Pb(Br0.17I0.83)3 formulation as the mixed cation and halide (MCH) perovskite and CuInS2 (CIS) as the inorganic hole transporting layer. The deposited MCH perovskite with uniform, compact and smooth microstructure containing equiaxed large grains showed excellent thermal and structural stability under intense conditions at 85 °C for 2 h in humid air (i.e., 45% relative humidity). Moreover, it had higher phosphorescence emission, absorption and... 

Because of the compatibility with tandem devices and the ability to be manufactured at low temperatures, inverted perovskite solar cells have generated far-ranging interest for potential commercial applications. However, their efficiency remains inadequate owing to various traps in the perovskite film and the restricted hole blocking ability of the electron transport layer. Thus, in this work, a wide-bandgap n-type semiconductor, 4,6-bis(3,5-di(pyridin-4-yl)phenyl)-2-phenylpyrimidine (B4PyPPM), to modify a perovskite film via an anti-solvent method is introduced. The nitrogen sites of pyrimidine and pyridine rings in B4PyPPM exhibit strong interactions with the undercoordinated lead ions in... 

Low-cost inorganic hole-transporting materials (HTMs) accompanied by a printable carbon electrode is an efficient approach to address the limitation of material cost of perovskite solar cells (PSCs) and get this technology closer to commercialization. The present work is focused on optimizing the Zn/Sn ratio of Cu2ZnSnS4/carbon hole collectors in n-i-p structured PSCs, where CuInS2/carbon is applied as the reference hole collector. This composition regulation is a solution to address the challenge of composition-related defects of the Cu2ZnSnS4 (CZTS) material. The Zn/Sn ratio was tuned by the initial proportion of the zinc precursor during the nanoparticle (NP) synthesis using a heating-up... 

Cu2ZnSnS4 (CZTS) is a good candidate for cost-effective perovskite solar cells (PSCs) due to its direct bandgap with a value of 1.4–1.5 eV. In this study, we investigate CZTS ink as an inorganic hole-transport-layer (HTL) in CsMAFAPbIBr mixed halide PSCs. We study the cell efficiency and hole extraction from the perovskite layer for different thicknesses of HTL. The optimized device exhibits better hole selectivity, and the best efficiency of the device (12.84%) is achieved for the CZTS layer with a thickness of 159 nm. The prepared samples were also tested by open-circuit voltage decay analysis and electrochemical impedance spectroscopies. Results show that the optimized device effectively...