Synthesis and characterization of all-inorganic (CsPbBr3) perovskite single crystals

This work investigates the synthesis of Cesium (Cs) based all-inorganic (CsPbBr3) perovskite single crystals (PSCs) at low temperatures (45 °C) for application in photosensitive devices

Review—Influence of Processing Parameters to Control Morphology and Optical Properties of Sol-Gel Synthesized ZnO Nanoparticles

ZnO has several potential applications into its credit. This review article focuses on the influence of processing parameters involved during the synthesis of ZnO nanoparticles by sol-gel method. During the sol-gel synthesis technique, the processing parameters/experimental conditions can affect the properties of the synthesized material. Processing parameters are the operating conditions that are to be kept under consideration during the synthesis process of nanoparticles so that various properties exhibited by the resulting nanoparticles can be tailored according to the desired applications. Effect of parameters like pH of the sol, additives used (like capping agent, surfactant), the effect of annealing temperature and calcination on the morphology and the optical properties of ZnO nanoparticles prepared via sol-gel technique is analyzed in this study. In this study, we tried to brief the experimental investigations done by various researchers to analyze the influence of processing parameters on ZnO nanoparticles. This study will provide a platform to understand and establish a correlation between the experimental conditions and properties of ZnO nanoparticles prepared through sol-gel route which will be helpful in meeting the desired needs in various application areas

A Generalized Inflated Geometric Distribution

A count data that have excess number of zeros, ones, twos or threes are commonplace in experimental studies. But these inflated frequencies at particular counts may lead to over dispersion and thus may cause difficulty in data analysis. So, to get appropriate results from them and to overcome the possible anomalies in parameter estimation, we may need to consider suitable inflated distribution. In this thesis, we have considered a Swedish fertility dataset with inflated values at some particular counts. Generally, Inflated Poisson or Inflated Negative Binomial distribution are the most common distributions for analyzing such data. Geometric distribution can be thought of as a special case of Negative Binomial distribution. Hence we have used a Geometric distribution inflated at certain counts, which we called Generalized Inflated Geometric distribution to analyze such data. The data set is analyzed, tested and compared using various tests and techniques to ensure the better performance of multi-point inflated Geometric distribution over the standard Geometric distribution. The various tests and techniques used include comparing the parameters obtained through method of moment estimators and maximum likelihood estimators. The two types of estimators obtained from method of moment estimations and maximum likelihood estimation method, were compared using simulation study, and it is found after the analysis that the maximum likelihood estimators perform better

Recent progress, fabrication challenges and stability issues of lead-free tin-based perovskite thin films in the field of photovoltaics

Lead-halide perovskite materials have fascinated incredible attention among the research communities due to their favorable electrical and optical properties for optoelectronics and photovoltaic application such as significant light absorption coefficient, higher values of diffusion length, carrier mobility, carrier lifetime, etc. However, lead toxicity as well as its low material stability makes it still far from commercialization. Finding of lead ion replacement is therefore needed to form environmental friendly perovskite materials that are called lead-free perovskites. Among different substitutions, tin is the most potential candidate that is also non-toxic. In this review, the recent development of tin-based lead-free perovskite thin films in photovoltaics research area during the period 2014 till now is summarized. Moreover, the technical challenges and the stability issues faced by them are also discussed. Further, it is suggested that more efforts are needed for the advancement of tin-based lead-free perovskite thin films based solar cells to bring up this field as a cost competent technology for long term sustainability

Down‐conversion materials for organic solar cells: Progress, challenges, and perspectives

Organic solar cells (OSCs) in terms of power conversion efficiency (PCE) and operational lifetime have made remarkable progress during the last ten years by improving the active layer materials and introducing new interlayers. The newly developed wide bandgap organic donor and low bandgap acceptor molecules covered the absorption from the visible to the near-infrared region. Whereas the incident high energy region (UV) is not in favour of OSCs. Its absorption causes thermalization losses and photoinduced degradation, which hinders the PCE and lifetime of OSCs. Recently, lanthanide and non-lanthanide-based down-conversion (DC) materials have been introduced, which can effectively convert the high energy photons (UV) to low energy photons (visible) and resolve the spectral mismatch losses that limit the absorption of OSCs in high energy incident spectrum. Furthermore, the DC materials also protect the OSCs from UV-induced degradation. The DC materials were also proposed to cross the Shockley-queisser efficiency limit of the solar cell. In this review, the need for DC materials and their processing method for OSCs have been thoroughly discussed. However, the main emphasis has been given on developing lanthanides and non-lanthanides-based DC materials for OSCs, their applications, and their impact on photovoltaic device performance, stability, and future perspectives

High performance non-fullerene organic photovoltaics under implant light illumination region

Implantable biomedical electronics, such as pacemakers, drug pumps, cochlear implants, cardioverter-defibrillators, and neurological stimulators, help humans to overcome various diseases. Currently, the power supply for these devices relies on small-size batteries, and replacement of the battery is required after running for a period of time. Recharging the battery could be a way to prolong the replacement cycle. Organic photovoltaics (OPVs) are a class of emerging photovoltaics, which are now becoming more practical with recently developed device and material engineering. The absorption of OPVs using a non-fullerene acceptor (NFA) could be extended to the near-infrared (NIR) region to cover the transmission window of human skin between 650 and 1000 nm. Motivated by this, we conducted a study of NFA-based OPVs under light irradiation of wavelengths of 650–1000 nm for implants. The devices using donor (PTB7-Th) and NFA (IEICO-4F) as the active material have strong absorption in the NIR region and obtained a promising power conversion efficiency (PCE) of 14.3% under the implant light illumination, compared to 8.11% when using a benchmark fullerene derivative-based acceptor (PC71BM). Importantly, the PCE and power density of the NFA-based OPVs are significantly higher than the previously reported fullerene-based OPVs devices. This study shows that NFA-based OPVs have high potential for future applications in powering implants, e.g., through charging batteries

Effectiveness of Solvent Vapor Annealing over Thermal Annealing on the Photovoltaic Performance of Non-Fullerene Acceptor Based BHJ Solar Cells

We explore two small molecules containing arms of dicyano-n-hexylrhodanine and diathiafulvalene wings terminated with benzothiadiazole linker, denoted as BAF-4CN and BAF-2HDT, respectively, as small molecule non-fullerene acceptors (SMNFAs) in organic solar cells. The proposed materials are mixed with a low band gap polymer donor PTB7-Th having broad absorption in the range of 400–750 nm to form solution-processed bulk heterojunctions (BHJs). The photoluminescence (PL) measurements show that both donor and acceptor can quench each other’s PL effectively, implying that not only electrons are transferred from PTB7-Th → SMNFAs but also holes are transferred from SMNFAs → PTB7-Th for efficient photocurrent generation. Furthermore, solvent vapor annealing (SVA) processing is shown to yield a more balanced hole and electron mobility and thus suppresses the trap-assisted recombination significantly. With this dual charge transfer enabled via fine-tuning of end-groups and SVA treatment, power conversion efficiency of approximately 10% is achieved, demonstrating the feasibility of the proposed approach

Indoor application of emerging photovoltaics—progress, challenges and perspectives

The development of solution-processed photovoltaic (PV) devices for indoor applications has recently attracted widespread attention owing to their outstanding potential in harvesting energy efficiently for low-power-consumption electronic devices, such as wireless sensors and internet of things (IoT). In particular, organic PVs (OPVs), perovskite PVs (PPVs) and quantum dot PVs (QDPVs) are among the most promising emerging photovoltaic technologies that have already demonstrated strong commercialisation potential for this new market, owing to their excellent yet highly tuneable optoelectronic properties to meet the demands for specific applications. In this review, we summarise the recent progress in the development of OPVs, PPVs and QDPVs for indoor applications, showing the rapid advances in their device performance in conjunction with highly diverse materials and device designs, including semi-transparent, flexible and large-area devices. The remaining challenges of these emerging indoor PV technologies that need to be urgently addressed toward their commercialisation, including, in particular, their limited stability and high ecotoxicity, will be discussed in detail. Potential strategies to address these challenges will also be proposed