Chris Bonasia
A recent breakthrough in transparent solar panels could seamlessly integrate clean energy into building design by transforming ordinary windows into power generators.
An international team of researchers at CITYSOLAR recently announced an efficiency record for transparent solar cells. The panels combine organic solar cells with perovskites to achieve an efficiency of 12.3%, moving closer to the average 21% efficiency of non-transparent panels.
“We are the first to achieve this with complete semi-transparency in a large area,” said team member Jessica Barichello, a post-doctoral researcher at the Centre for Hybrid and Organic Solar Energy in Rome.
Barichello told The Energy Mix the researchers used a Bragg reflector—“a multilayer optical structure designed to reflect specific wavelengths of light while allowing others to pass through”—to improve efficiency. The reflector helped to increase density without significantly compromising transparency.
Transparent solar panels are meant to replace windows on commercial buildings for integrated electricity generation. CITYSOLAR has received €4 million (C$6.2 million) from the European Union for its efforts toward decarbonizing the building sector, which accounts for 40% of the bloc’s carbon dioxide emissions, reports The Independent.
“The large glass facades found in modern office buildings can now be used for energy production without requiring additional space or special structural changes,” said Prof. Morten Madsen, another CITYSOLAR researcher, from the University of Southern Denmark. “This represents a massive market opportunity.”
CITYSOLAR’s panels are between a technology readiness level of five and six, meaning they’ve been proven in a lab but without a developed prototype. They are not yet ready for real-world application.
Barichello said the panels are undergoing thermal and light stress tests, but initial life cycle assessments suggest they offer “environmental advantages compared to silicon cells.”
However, tests have not yet compared the modules’ performance as windows—including their lifespan and insulative properties—with the non-solar-photovoltaic commercial windows currently used on office buildings and skyscrapers. Commercial windows typically last from 15 to 30 years.
Barichello said the panels could also be used for agrivoltaics.
“With its high transparency, our demonstrator presents a potential solution for agrivoltaic systems, enabling sufficient light penetration for crops while simultaneously producing energy to meet a portion of energy needs,” she told The Mix.
Vitaliy 
Mitchell Beer 
Promising step, but a lot left to prove
This 12.3% efficiency record for transparent solar is a strong step forward, especially since we’re talking large-area, fully semi-transparent panels. That matters. But let’s not get carried away yet.
We’re still in tech readiness levels 5–6, which means this is promising lab work, not install-ready hardware. No prototypes tested in real-world building envelopes yet. That’s key, because glass isn’t just a light filter—it’s insulation, weatherproofing, and safety.
No data yet on lifespan, U-values, or whether these hold up like commercial-grade double-glazing (which lasts 15–30 years). Until they match or beat the thermal and structural performance of standard windows, adoption will be a slow climb, especially in cold-weather zones like Canada.
Still, the upside is real. Office towers with curtain walls, greenhouses, agrivoltaics—these are great fits. I’ve worked on a few retrofit projects where clients asked about BIPV options, but we had to walk away because of cost, complexity, or poor light output. If CITYSOLAR’s panels clear those hurdles and stay affordable, they could unlock a new layer of energy generation for urban spaces.
Just don’t mistake potential for deployment. The real test starts once these hit pilot installations. Keep expectations steady—but yes, this tech is worth watching. https://solarenergies.ca
Thanks for this. We read the story the same way, and purposely reported it to avoid any implication that transparent solar is ready for prime time…yet. It’s fun, promising, and as you say, legitimately progressing. But no one should be including it an energy futures model just yet. That’s what we were saying about offshore wind and batteries a dozen years ago, because we didn’t know then what we know now. But it’ll be a while longer before any of us can say how or whether the trajectories compare.
Side bet: Which technology will be ready for prime time first, transparent solar or nuclear fusion? And if I lose the bet, can I buy my daughter a(nother) glitzy dessert? (Click the link if you’re wondering how in the world I connect *those* dots.) https://energymixweekender.substack.com/p/nuclear-fusion-shiny-objects-and