Diego Bagnis

Photovoltaics (PVs) are a critical technology for curbing growing levels of anthropogenic greenhouse gas emissions, and meeting increases in future demand for low-carbon electricity. In order to fulfill ambitions for net-zero carbon dioxide equivalent (CO₂eq) emissions worldwide, the global cumulative capacity of solar PVs must increase by an order of magnitude from 0.9 TW_p in 2021 to 8.5 TW_p by 2050 according to the International Renewable Energy Agency, which is considered to be a highly conservative estimate. In 2020, the Henry Royce Institute brought together the UK PV community to discuss the critical technological and infrastructure challenges that need to be overcome to address the vast challenges in accelerating PV deployment. Herein, we examine the key developments in the global community, especially the progress made in the field since this earlier roadmap, bringing together experts primarily from the UK across the breadth of the PVs community. The focus is both on the challenges in improving the efficiency, stability and levelized cost of electricity of current technologies for utility-scale PVs, as well as the fundamental questions in novel technologies that can have a significant impact on emerging markets, such as indoor PVs, space PVs, and agrivoltaics. We discuss challenges in advanced metrology and computational tools, as well as the growing synergies between PVs and solar fuels, and offer a perspective on the environmental sustainability of the PV industry. Through this roadmap, we emphasize promising pathways forward in both the short- and long-term, and for communities working on technologies across a range of maturity levels to learn from each other.

Two different methods are used to deposit Nb₂O₅ as compact electron transport layers in n-i-p double cation mixed-halide perovskite Cs_0.17FA_0.83Pb(I_0.83Br_0.17)₃ solar cells: reactive sputtering and spin coating. These different Nb₂O₅ films influenced perovskite growth and the charge transport in the cells. Photovoltaic parameters were obtained with an average power conversion efficiency of 17.0% and 15.7% for the devices based on sputtered and spin-coated Nb₂O₅, respectively. The mobility and the extracted charges were higher in sputtered Nb₂O₅-based devices than in the spin-coated ones. This effect is attributed to the larger grain sizes observed in the perovskite films when deposited onto the sputtered Nb₂O₅ layers. The higher densities of grain boundaries in the spin-coated Nb₂O₅-based devices increase ion diffusion and are expected to decrease efficiency.

The development of new energy technologies is crucial for climate stability and planet security. The growing energy demand has driven several researches aiming increase the supply of electricity, nationally and globally. The depletion of some energy resources makes it necessary to expand the forms of energy generation, materials and technologies used. Given this scenario, polymeric photovoltaic solar cells offer a potential route for implantation of large-scale solar energy once they enable cost reduction, using materials abundant in nature and low-cost production technologies. Polymeric solar cells, composed of organic materials, can be used both as an alternative in energy production. In this research work, a study was carried out on the production process and working mechanisms of polymeric solar cells. The studied devices were produced by a blade coating method, with active layer composed of hybrid films polymer:fulerene based on poly(3-hexylthiophene-2,5-diyl) (P3HT):[6,6]-phenyl-C61- butyric acid methyl ester (PCBM). The evaluated photovoltaic parameters presented small dispersion values, suggesting that the employed method proved to be efficient in the fabrication of the devices. The energy conversion efficiency of the photovoltaic device with the best performance was estimated to be around 3.12%.

Accurate prediction of the future performance and remaining useful lifetime of next‐generation solar cells such as organic photovoltaics (OPVs) is necessary to drive better designs of materials and ensure reliable system operation. Degradation is multifactorial and difficult to model deterministically; however, with the advent of machine learning, data from outdoor performance monitoring can be used for understanding the relative impact of stress factors and could provide a powerful method to interpret large quantities of outdoor data automatically. Here, we propose the use of artificial neural networks and regression models for forecasting OPV module performance and their degradation as a function of climatic conditions. We demonstrate their predictive capability for short‐term energy forecasting of OPV modules, showing that energy yield can be predicted if climatic conditions are known. In addition, the model has been extended so that the impact of climatic conditions on degradation can be predicted. The combined model has been validated on unseen OPV module data and is able to predict energy yield to within 4% accuracy.

Low‐light applications provide an exciting market opportunity for organic solar cells (OSCs). However, so far, studies have only considered OSCs of limited commercial viability. Herein, the applicability of a fully‐scalable, flexible, inverted non‐fullerene acceptor (NFA) containing OSC is demonstrated by showing its superior performance to silicon under low‐light, achieving 40 µW cm⁻² maximum power output at 1300 lx illumination. The effect of parasitic resistance and dark current on low‐light performance are identified. Furthermore, an atmosphere sensitive light‐soaking (LS) effect, critical for low‐light performance and resulting in undesirable S‐shaped current‐voltage characteristics, is analyzed. By employing different interlayers and photoactive layers (PALs) the origin of this LS effect is identified as poor electron extraction at the electron transport layer (ETL)/PAL interface when the common ETL ZnO is used. Two strategies are implemented to overcome the LS effect: replacement of ZnO with SnO₂ nanoparticles to reduce ETL sub‐gap electron trap states or tuning the NFA energy levels to optimize interfacial energetics. Finally, the commercial viability of these LS‐free devices is demonstrated by fabricating fully printed large‐area modules (21.6 cm²) achieving a maximum power output of 17.2 µW cm⁻², providing the most relevant example of the currently obtainable performance in commercial low‐light OSCs.

Tests on organic photovoltaics (OPV) mini modules, fabricated through a R2R process, in air and without hazardous solvents have been conducted in order to compare their outdoor performance, in Belo Horizonte, Brazil, and Bangor, North Wales, and assess the impact of the latitude and climate of the installation on the power generation and modules' lifetime. The test showed different profiles of degradation for each region and formulation, with a surprisingly faster degradation in Bangor. One of the possible sources of the increased degradation is the greater levels of condensation observed in Bangor. To verify the impact of condensation on the module stability, indoor tests have been conducted to relate the dew point depression to module degradation times. The results show that condensation is a significant stress factor in OPV and should be considered more prominently in reliability studies.