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The photovoltaic effect is where light striking a material generates electric current and was first observed in the mid-1800s. Early photovoltaic devices were expensive, made from toxic materials, and converted less than 1% of sunlight into electricity. At the same time, fossil fuels were becoming cheap and readily available, offering far more practical energy. Photovoltaic research languished for nearly a century.

The modern solar era began in the 1940s-50s when Bell Labs researchers, building on semiconductor science, developed silicon-based solar cells that achieved 6% efficiency, a dramatic improvement but still far too expensive for widespread use outside specialized applications like spacecraft. Over the following decades, incremental advances steadily improved silicon solar cell efficiency while manufacturing innovations reduced costs. This process took more than 60 years: silicon cells now exceed 26% efficiency in the laboratory and 20-22% in commercial panels, while costs have decreased several hundred-fold.

Today, electricity from silicon photovoltaics is cost-competitive with fossil fuel generation in most locations, and often cheaper when considering full lifecycle costs. In many regions, solar is now the most affordable electricity source available. This economic transformation positions solar power as a central technology for clean energy systems. However, scaling solar from its current ~5% of global electricity to a dominant role requires addressing remaining technical, economic, and deployment challenges across the full technology pipeline.

RASEI's solar research spans this entire pipeline, from fundamental materials physics and materials science, through device engineering to real-world deployment and end-of-life management. Working across multiple photovoltaic technologies and scales of application.

Perovskite photovoltaics have achieved unprecedented efficiency improvements, from 4% in 2009 to over 26% today, while offering potential manufacturing cost advantages through low-temperature, solution-based processing. RASEI has substantial research efforts in perovskite solar cells, addressing the key challenges of stability, lead-free alternatives, and scalable manufacturing that must be solved before perovskites achieve widespread commercial deployment.

Single-junction solar cells, whether silicon, perovskite, or other materials, face fundamental efficiency limits because they can only optimally convert a portion of the solar spectrum. Higher-energy photons waste energy as heat; lower-energy photons aren't absorbed at all. Tandem cells stack materials with different bandgaps, allowing each layer to efficiently convert a different portion of the spectrum. Perovskite-silicon tandems have achieved over 33% efficiency in the laboratory, significantly exceeding what either material can achieve alone.

RASEI research on tandems addresses multiple challenges: developing top-cell materials (often perovskites or other thin films) optimized for tandem configurations, engineering transparent contacts and interfaces between layers, managing thermal and mechanical stresses from combining different materials, and developing manufacturing processes that integrate these distinct technologies without damaging either layer. Tandem architectures offer a pathway to dramatically higher efficiencies, particularly valuable for applications where space is limited (rooftops, vehicles) or where higher efficiency justifies higher cost (concentrated solar, space applications).

Beyond silicon and perovskites, RASEI explores other thin-film photovoltaic materials including organic solar cells. These technologies offer distinct advantages: lightweight and flexible form factors, potential for very low manufacturing costs through roll-to-roll printing processes, transparency options for windows and building integration, and reduced material usage compared to silicon wafers.

The tradeoff is typically lower efficiency and shorter lifetime compared to silicon. Research focuses on improving both, designing materials with better charge transport and light absorption, understanding and preventing degradation mechanisms, and developing device architectures that maximize performance. For applications where flexibility, weight, aesthetics, or very low-cost matters more than efficiency, these technologies offer compelling advantages.

Translating laboratory cell performance to commercial modules requires addressing numerous engineering challenges. Small laboratory cells (often <1 cm²) achieve higher efficiencies than large commercial panels because scaling introduces losses, such as non-uniform materials over large areas, electrical resistance in conductors and contacts, optical losses from encapsulation and protective layers, and mechanical stresses from temperature cycling and environmental exposure.

RASEI research develops accelerated testing methods that predict long-term performance and reliability from short-term experiments, engineers module architectures that minimize scaling losses, optimizes encapsulation materials and methods that protect cells while maximizing light transmission.

Solar panels don't operate in isolation, they are part of larger energy systems. Research addresses how solar integrates into these systems across multiple scales: Utility-scale solar farms (megawatts to gigawatts) require optimizing panel placement and orientation, integrating with grid infrastructure and managing large power flows, pairing with energy storage to provide power when the sun isn't shining, and coordinating with other generation sources. RASEI research on grid integration addresses how large-scale solar affects grid stability and operations. Rooftop and distributed solar (kilowatts per installation) faces different challenges: diverse roof orientations and shading conditions, integration with home or building electrical systems, economics of residential-scale storage, and navigating permitting and interconnection processes. Research examines how distributed solar and storage can provide grid services.

As the solar industry matures, managing end-of-life becomes increasingly important. Early solar panels are now reaching the end of their 25-30 year lifespans, and the volume of retired panels will grow substantially over coming decades. Panels contain valuable materials (silicon, silver, copper, aluminum, glass) that could be recovered and reused, but current recycling infrastructure is limited. RASEI research and analysis on solar circularity examines processes for efficiently recovering materials from different panel types (silicon, thin films, emerging technologies each require different approaches), designing new panels for easier disassembly and material recovery, economic and policy frameworks that incentivize recycling rather than landfilling.

Technical performance alone doesn't determine solar deployment success. RASEI researchers study how different communities experience solar adoption. This real-world deployment research informs both technology development and policy design.

Solar photovoltaics have achieved remarkable technical and economic progress, transforming from an expensive niche technology to the lowest-cost electricity source in many regions. However, scaling solar to provide a dominant share of global electricity, and doing so equitably across diverse communities and applications, requires continued advances across the full technology pipeline.

RASEI's comprehensive approach addresses this challenge at every stage: fundamental research improving materials and devices, engineering work translating laboratory performance to commercial products, systems research integrating solar into grids and buildings, deployment analysis understanding and overcoming adoption barriers, and circularity research ensuring sustainable end-of-life management. By working across these dimensions and across multiple photovoltaic technologies, RASEI research advances solar power as a cornerstone of clean, affordable, accessible energy systems.