Perovskite solar cells (PSCs) are solar cells that are efficient, low cost, and simple to fabricate. Over the last 9 years, researchers have conducted in-depth research on PSCs to increase their photoelectric conversion efficiency from 3.8% to 24.2%. PSCs have the potential to replace traditional energy sources in the future. However, the stability of these cells is poor, which limits their practical applications, because the perovskite material is susceptible to degradation by environmental factors, such as moisture, heat, and oxygen. In our review, some studies related to improving the stability of PSCs are summarized. Strategies that have been developed to improve the stability of PSCs are reviewed from the aspects of the electron transport, perovskite, and hole transport layers (HTLs). These strategies include doping the electron transport layer (ETL), using dopant-free HTL, grain passivation, employing double layers or graded hybrid structure of ETL or HTL, two-dimensional perovskites, and so on. We provide a reference for future studies on the stability of PSCs.

Guest editors introduce the articles in the Special Section on Solar Energy Solutions for Electricity and Water Supply in Rural Areas, published in Volume 9, Issue 4 of the Journal of Photonics for Energy.

Concentrator photovoltaic (CPV) technology is one of the best available technologies to use sunlight efficiently. Nonimaging optical elements have been used for the development of CPV systems for delivering uniform flux distribution, which gives a high optical efficiency. This research presents optical modeling of a CPV system, which consists of a primary parabolic trough and a secondary nonimaging reflector. The proposed concentrating system is capable of providing high concentration. In the literature, parabolic trough-based CPV systems included multijunction solar cells in a linear array, which provided low concentration about 50  ×   on the solar cells. The proposed design sets the solar cell at the center of the trough in a square shape, which achieves a geometrical concentration of 285, acceptance angle of ±1.1  deg, and optical efficiency of 72%. The detailed architecture design and optical ray-tracing simulation are presented to show the innovative idea for harnessing solar energy using the parabolic trough concentrator.

The zero energy building (ZEB) concept mainly depends on the dual-nature of the building attached photovoltaics systems acting as active elements for energy generation as well as shading elements for energy savings. Previous studies have shown that the maximum energy savings occur when the internal heat gains and the internal lightings consumption are reduced and also thermal insulating materials are used in building construction. Our study aims to achieve a ZEB under Egyptian climatic conditions using photovoltaic integrated shading (PVIS) systems. This is done by simulating an office building using thermal-insulation layers in wall and roof construction. Moreover, a concept is applied through using the PVIS system on windows to act as an energy generation and energy saving element. Several simulation scenarios were conducted using Sketchup and EnergyPlus software while testing the effect of using PVIS as well as the effect of having insulation layers. Results show that the best annual net energy was generated in the case of the office model with PVIS system at a tilt angle of 60 deg and a projection factor 0.7 with air conditioning set at 21°C for heating and 26°C for cooling with glass wool insulation layers with a thickness of 0.1 m (double thickness) on the walls, and an extruded polystyrene insulation layer with thickness 0.11 m (double thickness) on the roof. This resulted in an annual monetary savings of 235%. Moreover, for all cases, the annual energy consumption, the annual net site energy, and the annual heating and cooling consumptions decrease with increasing the insulation layer thickness. The percentage annual energy savings were in the range of 50% to 80% depending on the test conditions, while the percentage annual monetary savings were in the range of 80% to 235%.

In Egypt’s remote areas, photovoltaic (PV) systems appear to be a promising technology to substitute diesel generators for water pumping in irrigation systems. We aim to minimize the installed PV capacity and investment costs by optimizing azimuth and tilt angles of the PV panels and to assess the complicity with pressure and water requirements. For this purpose, a numerical algorithm has been developed for a PV-driven drip irrigation system without a water storage tank in the Bahariya Oasis, Egypt. Crop water demand is considered by 7.8 ha plots planted with potato, tomato, and date palm. Nominal water flow rate is 86, 102, and 128  m³ h^−  1. For 128  m³ h^−  1, the optimization results in tilt angles for south orientation in the range of 40 deg to 50 deg, 10 deg to 20 deg, and 0 deg to 5 deg for potato, tomato, and date palm plots, respectively. In addition, for tomato and date palm plots with 86 and 86  /  102  m³ h^−  1, respectively, an east–west orientation with tilt angles of 55 deg to 60 deg is optimal. In this case, the system operates mainly in the self-compensated pressure range of the drip lines, which is assumed to guarantee proper water distribution across the field. However, the required PV peak power is large compared to the system settings with larger nominal water flow rates.

The technical and the social feasibility of using solar-powered ultraviolet light-emitting diode (UV-LED) module for a microbial water treatment system in Panobolon Island, Central Philippines, were investigated. Technical feasibility was assessed through a laboratory scale prototype and water point source sampling in nine selected deep wells of Panobolon Island. On the other hand, social feasibility was determined from survey responses of the island residents. Results revealed that (1) regulated solar power is a suitable alternative power source for UV-LED apparatus, (2) all water point sources tested in Panobolon island were positive for Escherichia coli contamination, and (3) the proposed system is socially accepted by the residents. Therefore, it can be concluded that the solar-powered UV-LED microbial water treatment system proposed is a viable solution to improve the quality of the drinking water consumed by the residents.

The lack of safe drinking water and electricity in rural areas of Sub-Saharan Africa is extremely alarming and, together with progressing climate change and political conflicts, increasingly impairing economic development. Only robust technologies of autonomous water treatment systems driven by solar electricity based on sustainable economic concepts can provide clean water and electricity at affordable prices. Technologies for water cleaning combined with off-grid electrification are analyzed for their suitability under different conditions, exemplified for Nigeria, and economically feasible concepts are developed for different target groups: (i) single-farmer concept providing electricity from PV, UV-treated drinking water and irrigation water, and generating income from selling increased crop yields; (ii) farmer cooperative; (iii) community concept, with additional income generation from selling water and electricity; and (iv) rural kiosk concept selling electricity and water, and offering further goods and services. In the latter three concepts, high quantities of drinking water and electricity are supplied by an autonomous, PV-driven water cleaning system with disinfection based on anodic oxidation and in situ chlorine production. Only if economically sustainable can drinking water and electricity supply be achieved at a global level, and the UN sustainable development goals be reached. In the framework of a rural community concept, a pilot project starts in Abuja/Nigeria based on the anodic oxidation system for water treatment with an intelligent payment systems and provision of solar-based electricity.

We focus on the potential of using solar PV powered, decentralized drinking water treatment technologies for providing communities in remote areas with safe drinking water. Small-scale, solar PV-powered solutions for water purification may help achieve the sustainable development goals in areas without electricity access. However, more field-based research on the performance of solar-powered drinking water technologies is needed in order to perfect existing technologies. We introduce the first longer-term applied field study on the performance of 16 solar PV-powered drinking water stations using greensand filters for iron removal and anodic oxidation for chlorine production in the oases across Egypt’s Western Desert. Local groundwater shows natural iron concentrations that in some places exceed the WHO standard (0.3  mg  /  l) by a factor of 50. The presented results show that the energy efficient, solar PV-operated stations successfully remove the iron from the water. Chlorine levels vary by location and are connected to local consumption patterns and site-specific system settings. Simple adjustments are needed in order to fully benefit from the solar-driven anodic oxidation process. Solar-powered technologies for drinking water purification need to be able to respond to specific local conditions in order to become an upscalable solution for remote, rural areas across the globe.

The United Nations Sustainable Development Goals (SDGs) and their interactions in developing countries in general, and in Egypt specifically, form the basis of our review. Issues of energy and water supply, linked to agriculture in rural areas, combine several of the SDGs. The current status and the challenges for solar photovoltaic (PV) electricity production and water supply technologies in rural areas are critically described and an outlook on future developments is provided. The framework of the water–energy–food nexus approach and its relation to the SDGs globally in the MENA region and in Egypt is presented and recommendations are given on institutional governance and research and development to overcome the silo mentality and enhance sector collaboration on all levels as prerequisite to achieving the SDGs. The latest technical developments in PV and water technologies and their opportunities for rural development are outlined. Combined technical solutions are highlighted with examples from Egypt. Specifically, installed systems in various rural locations are presented, and their advantages and shortcomings are discussed. The review provides a context for the studies presented in the Special Section on Solar Energy Solutions for Electricity and Water Supply in Rural Areas, Journal of Photonics for Energy, Volume 9, Issue 4.

A neural network maximum power point tracking (MPPT) controller has been proposed in order to improve the performance of a photovoltaic water pumping system. The proposed neural network MPPT controller has been trained using inputs and output data collected using the conventional P&O algorithm. The efficiency of the proposed algorithm has been studied successfully using a DC motor-pump powered by 36 PV modules via a DC-DC boost converter controller using the proposed neural network MPPT algorithm. Comparative study results between the proposed neural network MPPT controller and P&O MPPT controllers using fixed and variable step size versions as well as experimental study results using the STM32F4 board in the hardware in the loop mode prove the efficiency of the proposed controller regarding all considered performances metrics, reducing as a consequence the response time and eliminating the steady-state oscillation leading by the way to an improvement of the whole system performances.

Intrinsic losses, including below-band gap, thermalization, mismatch angle, Carnot, and emission, are investigated in a structure of quantum dot intermediate band solar cells (QD-IBSCs). Owing to the excellent irradiance resistance of III-nitride material and reduction of Auger recombination processes, diluted nitride of InAsN is considered as quantum dot (QD) material. Then, AlPSb is considered as the barrier material according to the principles of intermediate band operation and the band structures of InAsN and AlPSb in which phosphorous molar fraction is optimized by the minimizing of total intrinsic losses. The engineering of QD size and period offers a way to engineer the confined energy levels within the QDs and ultimately the intrinsic losses. This was carried out with the help of a finite element model in the context of a three-dimensional Schrödinger equation created by means of MATLAB software and tight binding method, resulting in the minimum intrinsic loss of 55.18% for the InAs_0.995N_0.005  /  AlP_0.7 Sb_0.3 QD-IBSC at 1-sun concentration.

Polymer solar cells (PSCs) have seen great progress in recent years, with power conversion efficiencies of over 15%. However, PSCs suffer from larger energy losses than inorganic and perovskite solar cells, leading to lower open-circuit voltage (V_OC). The main factors that hinder the V_OC improvements include (i) relatively large nonradiative recombination losses and thus low electroluminescence quantum efficiency (EQE_EL) in PSCs and (ii) the existence of a charge transfer state at the interface of donor and acceptor. For efficient charge separation in state-of-the-art PSCs, empirically, the driving force for exciton dissociation is considered to be at least 0.3 eV. The large driving force could lead to large voltage losses and thus hinder the PSC performance. In this study, we report using wide bandgap material PB3T as electron donor and low bandgap material IEICO-4F as electron acceptor for nonfullerene PSCs with very small driving forces, which, however, show a decent maximum external quantum efficiency (EQE) of nearly 40%. Moreover, we demonstrate a nonfullerene PSC with high EQE_EL up to 5.1  ×  10^−  4, corresponding to very low nonradiative recombination losses of 0.20 eV and overall photovoltage energy losses of 0.46 to 0.52 eV, derived from different bandgap (E_gap) determination methods, which can now be comparable to those in perovskite solar cells and inorganic solar cells.

MoO₃ and MoO₃  :  Eu^3  + films were synthesized by the pyrosol method. X-ray diffraction diffractograms, acquired as a function of the deposition temperature, indicated the orthorhombic crystalline structure for all studied MoO₃ films. Photoluminescence (PL) and cathodoluminescence (CL) characteristics of these films were measured as a function of deposition parameters, such as the substrate temperature and the doping content (Eu^3  +ions). As the deposition temperature was increased, an increase in the intensity of the PL and CL emissions was observed. Also, a quenching of the PL and CL, as a function of the doping content, was observed. Quantum efficiency measurements showed an average value as high as 54% and a pure red color was perceived. The elemental composition of the films as determined by x-ray photoelectron spectroscopy is reported as well. Additionally, the surface morphology features of the films, as a function of the deposition temperature (by means of scanning electron microscopy and transmission electron microscopy measurements) are exhibited. Moreover, Raman spectroscopy and decay time measurements were performed on some MoO₃  :  Eu^3  + samples.