The role of transport layers (TLs), such as the electron transport layer (ETL) and hole transport layer (HTL) in the perovskite solar cells (PSCs), play an important role in charge separation and transportation to the respective electrodes. Due to high bandgap, excellent electron mobility, and proper electron affinity, ZnO nanorod (NR) can be an efficient ETL for PSCs. Herein, we have numerically simulated the basic working mechanism of different concentrated Ni-doped ZnO NR ETL-based FTO/TiO2/Ni-ZnO NR/CH3NH3PbI3/Spiro-MeOTAD/Ag structured PSCs using a solar cell capacitance simulator one-dimension (SCAPS 1D) software. The simulated photovoltaic (PV) parameters yielded the highest device performance with power conversion efficiency (PCE) of 16.25 %, short circuit current density (JSC) of 20.67 mA/cm2, open circuit voltage (VOC) of 1.09 V, and fill factor (FF) of 71.52 % in the 4 M% of Ni-doped ZnO NR ETL-based PSC. The performance for the 4 M% Ni-doped ZnO NRs as ETL was much better compared to pure ZnO NRs as ETL. Motivating by this enhanced PV performance, we have fabricated PSCs using FTO/c-TiO2/ETL/CH3NH3PbI3/Spiro-MeOTAD/Ag device architecture, compared the device performances in between pure ZnO and Ni-ZnO ETL-based PSCs, and achieved a PCE of 6.52 %, JSC of 20.67 mA/cm2, VOC of 0.86 V, and FF of 36.32 % in the Ni-ZnO ETL with 0.25 cm2 active area. This experimental verification of the proposed numerical modeling of the device structure can make a truthful acceptance of the modeling and also show possible routes for further improvement in the device performance.

Iodine‐based hybrid planar perovskite solar cells’ (PSCs) overall performance is still very limited. In this work, a highly functionalized iodine‐based hybrid perovskite layer is fabricated by incorporating trimethylolpropane ethoxylated triacrylate (TET) within the perovskite precursor, which can crosslink with the grain boundaries to improve the crystallinity as well as the grain size and passivate the defect states of the perovskite material. The MAPbI 3 ‐based thin films with TET exhibited large grain sizes from 195.73 to 587.49 nm with 8 mg mL −1 of TET concentration. The X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), energy dispersive X‐ray (EDX) elemental mapping, photoluminescence (PL), and time resolved photoluminescence (TRPL) characterization results suggest the strong crosslinking effect between TET and MAPbI 3 , which improves the crystallinity and reduces the charge trap density. Planar PSCs is fabricated with the device architecture fluorine‐doped tin oxide (FTO)/c‐TiO 2 /MAPbI 3 :TET/Spiro‐MeOTAD/Au and achieved a power conversion efficiency (PCE) of 14.75% under 1.5 AM light illumination. The fabricated PSCs shows excellent ambient stability which retains 80% of their PCE after being exposed to the ambient environment of relative humidity (RH) ≈60%, room temperature (RT) ≈27 °C without any encapsulation.

Improving perovskite film quality for reducing non-radiative recombination centers is one of the key aspects of designing efficient and stable perovskite solar cells (PSCs). In this work, we fabricated a high-performing and ambient stable CsPbIBr2-based PSC by incorporating a 2D perovskite framework within a 3D perovskite structure. An optimum amount of 2D doping can anchor the grain boundaries to improve the crystallinity and grain sizes and ultimately suppress non-radiative recombination centers within the perovskite. The solution-processed perovskite film with the structural formula ((PEA)2PbI4)X(CsPbIBr2)1-X for X = 0.02 exhibited an improved average grain size of 853.38 +/- 0.18 nm in comparison to 350.43 +/- 0.09 nm of pristine CsPbIBr2 thin films. The bulk passivation within the perovskite was supported by the X-ray diffraction, steady-state, and time-resolved photoluminescence results. We fabricated a PSC with the device structure FTO/c-TiO2/m-TiO2/(PEA)2PbI4)X(CsPbIBr2)1-X/Spiro-OMeTAD/Ag, and achieved a power conversion efficiency (PCE) of 10.13% under ambient conditions with X = 0.02 and only 8.08% PCE for the pristine 3D perovskite (X = 0) device. The devices with 2D incorporation showed excellent ambient stability without any encapsulation and retained 80% of their initial PCE (T80) after 500 hours of ambient storage, whereas the device with pure 3D perovskite retained only 20% of its initial PCE after 400 hours of ambient storage. Simulation results, in combination with the experimental data, show that a reduced density of recombination centers resulted in much improved device performance.

Efficient and stable large-area perovskite solar cells (PSCs) are essential for the translation of the technology. However, the fabrication of large-area PSCs remains very challenging. Uniformity and homogeneity of different layers of a device over a large area are concerning issues. Poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine] (PTAA) has shown excellency as a hole transport layer (HTL) due to its stability and homogeneity over large areas. This work focuses on large-area (2.0 cm2) PSCs using PTAA as HTL with a device structure of FTO/m-TiO2/RbCs(MAFA)PbI3/PTAA/Ag. This PSC yields a power conversion efficiency (PCE) of 9.35% and retains 72% of the initial PCE even after 2000 h of storage in ambient conditions, which is optimistic for the translation of the technology. The uniformity of the PTAA layer over the large area and proper band alignment at interfaces result in good performance of PSCs. A numerical model is studied for further optimization of this PSC. A large-area monolithic tandem PSC is demonstrated using RbCs (MAFA)PbI3/PTAA combination along with a low bandgap perovskite, yielding a PCE of 21.85% with a VOC of 1.83 V, which is quite significant for an active area of 2 cm2. Therefore, this research will aid success in developing effective and stable large-area PSCs.

We have grown vertically ZnO nanorods (NRs) doped with Cu and Ni to modulate their electronic properties. The wurtzite structure of the ZnO NRs was confirmed from the top-view field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) images as well as X-ray diffraction (XRD) spectra, and the phase purity was confirmed by Raman spectroscopy. The NRs exhibit high texture orientation in the (002) and (100) directions of the Ni- and Cu-doped ZnO NRs, respectively. This structural modification significantly modulates their electronic properties. Scanning tunneling spectroscopy (STS) and corresponding density of states (DOS) measurements were employed to determine the electronic band gap and band-edge shift of the doped ZnO NRs. Ambient-processed semitransparent CsPbBr3 perovskite solar cells (PSCs) were fabricated with the device structure (FTO/ZnO seed layer/ZnO NRs:CsPbBr3/Spiro-MeOTAD/ITO) using these NRs as the electron transport layer (ETL). The Ni-doped ZnO NR samples were found to be very good in electrical conductivity with a low electronic band gap, which yielded a device power conversion efficiency (PCE) of 4.94% under ambient conditions. Thus, Ni-doped ZnO NRs could be used as an efficient low-cost and ambient-processed one-dimensional ETL in the fabrication of optoelectronic devices.

The CsPbI 2 Br material benefits perovskite solar cells (PSCs) by balancing their efficiency with chemical and thermal stability. Herein, we performed numerical modeling of a p-i-n structured PSCs employing different electron transport layers (ETLs). In order to optimize the ETL, the simulation results showed bilayer ETL (PCBM/SnO 2 ) yielded the best device performance. Then, by tweaking the absorber layer’s defect density, thickness, electron affinity, and band gap, we optimized the device performance utilizing this bilayer ETL and yielded power conversion efficiency ( PCE ) of 12.51%, fill factor ( FF) of 73.60%, open circuit voltage ( V OC ) of 0.94 V, and short circuit current density ( J SC ) of 17.94 mA cm −2 . These CsPbI 2 Br perovskite-based devices would have outstanding thermal stability in a range from 253 K to 323 K. Another important observation in these PSCs is that interfacial defect density plays a crucial for regulating the V OC . We, therefore, anticipate that this research will aid in the development of extremely effective and stable inverted all inorganic PSCs.

All inorganic CsPbBr3-based perovskite solar cells (PSCs) have drawn great attention from researchers because of their high chemical and thermal stability in an open environment. In this work, we successfully replaced the high-temperature deposited mesoporous caping (m-TiO2) electron transport layer (ETL) with a low-temperature deposited aluminum-doped zinc oxide (AZO) ETL and fabricated all inorganic CsPbBr3 PSCs using copper(I) thiocyanate (CuSCN) as a hole transport layer (HTL). The fabricated AZO-based devices exhibited an excellent power conversion efficiency (PCE) of 6.42%, fill factor (FF) of 60.32%, open-circuit voltage (V-OC) of 1.01 V, and short-circuit current density (J(SC)) of 10.38 mA/cm(2), whereas m-TiO2-based devices exhibited PCE of 5.33%, FF of 62.88%, V-OC of 1.02 V, and J(SC) of 8.39 mA/cm(2) under ambient conditions. In terms of stability, the AZO-based device retained 94% of its initial PCE, whereas the m-TiO2-based device retained 69% of its initial PCE after 1000 h of continuous exposure in the ambient atmosphere of relative humidity similar to 81% and room temperature (RT) similar to 27 degrees C without any encapsulation. Therefore, this approach of replacing m-TiO2 with AZO can facilitate the fabrication of efficient and highly stable planar all-inorganic PSCs in an ambient environment. In addition, we represented a cheap encapsulation process for improved stability as an additional advantage.

The development of ambient stable and large-area inorganic-organic hybrid perovskite solar cells (PvSCs) is necessary to translate the technology into our daily life. The concerning issue is that the materials are easily degradable and need proper attention toward the degradation mechanism. A polymer material, PTAA, can be used for the hole transporting layer (HTL) of the PvSCs, which may have better stability. This work focuses on the impact of the polymer PTAA on the stability of mesoporous n-i-p structured RbCs(MAFA)PbI3-PvSCs while using silver (Ag) as a top electrode and, in other cases, gold (Au) as the top electrode. Comparing the device performance with two different electrodes (Ag and Au) over small (0.25 cm(2)) and large areas (1.0 cm(2)), the critical role of the HTL material in the stability and performance of a fabricated device has been demonstrated here. The PTAA/Ag and PTAA/Au combination-based devices showed almost the same performance. The unencapsulated Ag electrode-based RbCs(MAFA)PbI3-PvSCs yielded a power conversion efficiency (PCE) of 10.29% over a 0.25 cm(2) active area. The fabricated device retains over 50% of its initial efficiency after 2000 h of storage in ambient conditions. At the same time, the PTAA/Au combination-based device showed better stability in ambient conditions. We chose the PTAA/Ag combination as a winner as it could provide a fast, easy, and cost-effective method for developing highly efficient, stable PvSCs.

We present experimental studies on doped and undoped ZnO nanoparticles prepared via cost-effective solution processing techniques towards its applicability for terahertz frequency domain. Scanning electron microscopy (SEM) confirms that the dimensions of synthesised particles spread over 120–275 nm, while x-ray diffraction (XRD) along with energy dispersive x-ray (EDX) characteristics manifests the presence of the desired materials for doped as well as undoped nanoparticles. Further, terahertz-time domain spectroscopy (THz-TDS) data are recorded in transmission mode which are employed to extract several optical parameters (viz. refractive index, conductivity, etc) of the nanoparticulate films spanning the frequency range from 0.2 to 0.9 THz. Doped samples clearly manifest enhanced conductivities because of the presence of metallic components. Cost-effective synthesis of ZnO nanoparticles can be useful for terahertz photonics in future.

p-i-n structured semitransparent perovskite solar cells have already been established as promising energy harvesting devices for building-integrated photovoltaics and flexible solar cells due to high transparency and low-cost fabrication. In this study, solution based p-i-n structured semitransparent perovskite solar cells (PSCs) have been developed using thin silver (Ag), zinc oxide (ZnO), and aluminium (Al)-doped ZnO nanoparticles (AZO) as buffer layers in addition to PCBM as an electron transport layer (ETL). The thickness of the ZnO and AZO layers are around ~100 nm. In the case of the thin Ag layer, poor interfacial band alignment and less transparency yield device performance with an inferior PCE of 2.53% when illuminated from the top electrode side. On the contrary, Al-doped ZnO possesses excellent optoelectronic performance as a buffer layer for their better electronic conductivity and interfacial band alignment and yield a photovoltaic device characteristic with a power conversion efficiency (PCE) of 5.87% when illuminated from the top electrode side, whereas the standard device with a metal electrode shows a PCE of 6.4%. The semitransparent device also has an average transparency of 21.8% in the visible region. Inverted structure semitransparent perovskite solar cells have been developed for flexible and building integrated photovoltaic (BIPV) applications. Solution processed perovskite solar cells with a power conversation efficiency of 5.87% and visible transmittance of 21.8% make an excellent candidate for BIPV and smart windows. Aluminum-doped zinc oxide (AZO) nanoparticles are found very effective buffer layer for the sputter grown top electrode over PCBM layer to reduce the interface damage and enhanced the overall photovoltaic performance.

This paper examines the empirical association between public issue and economic development (GDP) during the period 1989-2009. With help of log-lin regression model, we found that public issue had a positive significant impact on India’s economic development during this period, which survives almost all diagnostic tests of Classical Linear Regression Model. But, the relationship between public issue and economic development during this period, though had drastically undergone a structural change after 1997 South-east Asian Crisis, evidenced by residuals of recursive least squares, CUSUM test, CUSUMSQ test and Chow’s Predictive Failure test, but had remained stable after 2007 Subprime Crisis.

This paper examines the empirical association between Foreign Direct Investment (FDI) and Economic development (GDP) in India during 20-year-period (1991-2010) in the post-reforms era. With help of time-series regression model, where GDP has been regressed on FDI, after making both the non-stationary series (FDI and GDP) stationary through 2nd differencing of Augmented Dickey-Fuller Test, it has been found that FDI had a negative impact, and that too marginally significant, on India’s economic development during this period, which is contrary to the common belief. The negative impact has been substantiated by the fact the growth rate of FDI inflow into the economy during this period was greater than growth rate of GDP, which implies some unabsorbed capital remained in the economy, leading to inflationary pressure, which, in turn, caused fall in the development of the real sector further, establishing a negative impact of FDI on economic development.

Data that represent complex and multivariate processes are well known to be multiscale due to the variety of changes that could occur in a process with different localizations in time and frequency. Examples of changes may include mean shift, spikes, drifts and variance shifts all of which could occur in a process at different times and at different frequencies. Acoustic emission signals arising from machining, images representing MRI scans and musical audio signals are some examples that contain these changes and are not suited for single scale analysis. The recent literature contains several wave let-decomposition-based multiscale process monitoring approaches including many real life process monitoring applications. These approaches are shown to be effective in handling different data types and, in concept, are likely to perform better than existing single scale approaches. There also exists a vast literature on the theory of wavelet decomposition and other statistical elements of multiscale monitoring methods, such as principal components analysis, denoising and charting. To our knowledge, no comprehensive review of the work relevant to multiscale monitoring of both univariate and multivariate processes has been presented to the literature. In this paper, over 150 both published and unpublished papers are cited for this important subject, and some extensions of the current research are also discussed.

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