Tuesday morning’s plenary lecture in Area 4 was given by Dr. Eszter Voroshazi from Univ. Grenoble Alpes (CEA-INES) which discussed the importance of sustainability when considering TW implementation of PV. This included considering the availability of materials and critical shortages of (for example) silver and indium particularly when considering current ambitions in terms of large-scale PV installations. Increasing efficiency was discussed as a critical lever towards sustainability, where multiple technologies must be used. In general, improvements and considerations in both module manufacture and their impact require assessment to provide sustainability during the clean energy transition.
The plenary in Area 7 was given by Jenya Meydbray from PVEL who discussed PV performance, reliability, and qualification using and various field-testing protocols including thermal cycling, mechanical stress, and damp heat testing etc., in addition to the effects of weather such as hail, tornados, snow loading etc. Developments in testing due to transitions from mono to bifacial and for new physically larger solar cells have also been developed, and testing assesses not only PV modules but constituent materials (encapsulants, contacts, cell busbars and soldering etc.).
Dr. Babak Enayati from New Technology National Grid gave Tuesday morning’s plenary lecture in Area 9 on “PV Grid Integration Challenges and the Need for Grid Enhancing Technologies.” Here, Dr. Enayati discussed how large-scale PV deployment might be incorporated on the grid in an affordable manner that enables a sustainable clean energy future. PV integration provides several challenges including issues with power quality – voltage fluctuations, system protection, power back feed into transmission (which increases with solar), and unintentional islanding (generation of power in subsection of grid). Enhancing grid capabilities were discussed with respect to the use of intelligent systems in terms of monitoring, protection, and ensuring the health of the infrastructure (transformers etc.) and implementing new tools such as robotics to assess live substations, and the integration of renewables (via storage and power flow control).
The Area 1 session on “Thermoradiative and Hot Carrier Devices” began with a presentation from Nicholas Ekins-Daukes from UNSW who gave a comprehensive introduction into the emerging topic of thermoradiative diodes bridging classical PV and thermoradiative systems and presenting strong experimental evidence for the viability of such systems. This was followed by a discussion of the theoretical limitations of thermoradiative devices from Geoffrey Landis from NASA Glenn Research Center who described practical losses with respect to terrestrial and space applications. Kyle Dorman from the University of Oklahoma described recent experimental work on the role of electric field in carrier scattering and extraction in valley photovoltaic systems, while Daixi Xia from the University of Ottawa discussed the development of a drift-diffusion model for such valley photovoltaic systems, which includes multi-valley transport and intervalley scattering transitions.
In Tuesday morning’s Area 2 session on the “Production and Reliability of CIGS” Simona Villa from TNO described how to employ multi-mode lab scale characterization techniques to identify nanoscale mechanisms of water ingress-induced degradation of fielded CIGS modules. Here, the degradation of CIGS modules due to water ingress was shown to be a serious issue for long term stability of the systems. Diego Colombara from the Universita degli Studi di Genova discussed a thought experiment on how preferential diffusion of sodium in CIGS could lead to anisotropyinduced fluctuations. Ayaka Yamada from the University of Tokyo described a photothermal AFM technique to directly measure non-radiative recombination at grain interiors and boundaries depending on Cs treatment, while Klaas Bakker (TNO partner in Solliance) identified that the connection between decomposition voltage and Cu content in CIGS is a fundamental material property of critical relevance for shading-induced degradation and the formation of worm-like features in the TCO.
Tuesday morning also saw a joint session between Area(s) 3.6 and 6.8 on “Perovskites and Chalcogenides for the Space Environment.” This included work from Kaitlyn VanSant from NASA Glenn/NREL who described the stability of triple cation perovskite solar cells encapsulated in ALD SnOx/ITO layers, which were shown to retain their performance under light exposure, high temperatures (384K) and vacuum for 3600 hours. Zhaoning Song from the University of Toledo presented excellent work on the development of high efficiency flexible all perovskite tandem solar cells with high specific power, while Hadi Afshari from the University of Oklahoma demonstration high temperature high radiation stability of perovskite solar cells with optimized structural design and encapsulation. Moving away from perovskites, Manoj Jamarkattel from the University of Toledo demonstrated the potential of flexible CdTe/CdS solar cells for space power applications presenting high performance low specific power devices in this system.
In the Area 4 session on “Passivated, Carrier-Selective, and Heterojunction Contacts” Thien Truong from the Australian National University discussed Gallium-Boron spin-on co-doping for polycrystalline silicon passivating contacts and described how while Ga doping provides promising passivation properties it has high contract resistivity, and that boron lacks passivation but shows good contact resistivity. Zhongshu Yang (ANU) discussed strong gettering observed for poly-Si contacts and proposed a model to describe the gettering through pinholes and in different oxides. Franz-Josef Haug from EPFL discussed fireable passivating tunnel oxide contacts for crystalline silicon solar cells and presented promising results on cubic SiC for more transparent poly-Si structures, while Wook-Jin Choi from Georgia Tech. described a streamlined process for front integration of thin Poly-Si passivating contacts using a novel co-annealing process.
In Tuesday morning’s session in Area 8, Jacob Clenney from Arizona State University reported on work related to the influence of Na from Glass on potential induced degradation (PID) effects using simulations, TOF-SIMS analysis, and modelling and showing that Na relevant for PID cannot originate in the glass substrate and production contamination is the most likely source. Patrick Thornton from Stanford showed improved predictions for the evolution of EVA adhesion based on modeling of field and accelerated ageing in various locations in the United States.
Tuesday Morning’s session in Area 9 discussed “Microgrids and Distribution System Operation and Control.” Highlights included Fernanda Trindade from the University of Campinas presenting a method for performing PV hosting capacity, which is much faster than traditional power flow approaches, and Nicholas Gurule from Sandia National Laboratories describing the droop response of grid-following and grid-forming inverters and showed how these control techniques can lead to instability. William Hobbs from the Southern Company also presented the challenges of estimating the potential high limit of PV output in real-time operation while the systems were being curtailed.
On Tuesday afternoon, the Area 11 session on “Environmental and Health Impacts” included highlights from Sherif Khalifa from Drexel University who discussed the health and toxicity risks of the lead-halide perovskites and found that lead leaching from perovskite modules stays below EPA limits depending on the inherent background lead levels in the soil. However, Gonzalo Rodriguez-Garcia from South Dakota School of Mines & Technology showed that other metals in perovskite modules need to be considered for total toxicity, especially in floating solar installations. Elsewhere, Parikhit Sinha from First Solar presented work that confirms that CdTe and c-Si PV systems meet electricity sector economic emissions intensity requirements for staying below the 1.5 °C set by the IPCC.
Highlights in the Area 5 session on “Advanced Characterization of PV Materials and Devices” included applications of Kelvin probe techniques to reveal the junction location in CdTe solar cells by Chun-Sheng Jiang from NREL, and work from Rasha Awni from the University of Toledo that showed capacitance-voltage analysis of perovskite solar cells can lead to an overestimation of the doping density in these systems. Vladislav Kornienko from Loughborough University described how Xe-plasma FIB techniques followed by electron back scattering diffraction allowed a large-area survey of grain orientation in CdTe thin film solar cells, which can be correlated to device efficiency.
Tuesday afternoon’s Area 9 session on “Ancillary Services and Grid Support Functionalities” covered topics which are critical to integrate large penetration of variable renewable energy (VRE) sources like solar PV and wind to the power grid in a safe and economic manner. Topics covered included effects of solar variability and location (Mesude Bayrakci Boz – Penn State Hazleton), ancillary services market potential for VRE (James Hyungkwan Kim - Stanford), gridfollowing and grid-forming inverters (Marena Trujilo – University of Colorado), and distribution system loading (Isacc Bromley-Dulfano – NREL).
Tuesday afternoon also saw an Area 3 session covering III-V Photonic Power Converters. Emily Kessler-Lewis from Rochester Institute of Technology presented the first experimental demonstration of a fully monolithic integrated electro absorptive modulator/PV device for free space optical communication, while Meghan Beattie from the University of Ottawa presented an InGaAs power converter on InP along with a metamorphic InGaAs device on GaAs demonstrating 52.8% efficiency in the O-transmission band. Jamie Phillips from the University of Delaware presented bio-integrated devices with over 10% efficiency and transmission of 850 nm illumination through mouse tissue. Further highlights included FDTD calculations from Nicholas Irvin from Arizona State University who showed that the combination of truncated nano cones and lower silver mirrors in thin GaAs diodes predict an almost 19% increase in the optical absorption under monochromatic illumination, and a presentation by Brian Corbett from Tyndall National Laboratory on the development of wide gap AlGaInP-based PV cells for indoor PV harvesting.