Tandem PV

(formerly iris pv)

the next evolution in photovoltaics


Tandem PV co-founders Colin Bailie and Chris Eberspacher.

Tandem PV co-founders Colin Bailie and Chris Eberspacher.

Co-founder Colin Bailie holds a B.S. in mechanical engineering from Texas A&M University and a M.S. and Ph.D. in materials science and engineering from Stanford University. During his graduate and post-graduate work, Bailie performed seminal research on perovskite tandem solar cells, including the first reports of mechanically-stacked perovskite on Silicon and CIGS tandems (Energy & Environmental Science, 2014) and monolithic perovskite on Silicon tandem (Applied Physics Letters, 2015), as well as breakthrough engineering solutions to enhance the thermal stability of perovskite solar cells (Advanced Materials, 2016), and thermal and humidity stability (Nature Energy, 2017), filing 4 patent applications in the process. Bailie was recognized for his accomplishments by inclusion in the 2016 Forbes 30 under 30 in Energy list. 

Co-founder and managing director Chris Eberspacher has extensive experience developing photovoltaic solar technology. He served as chief technology officer at SoloPower Systems where he managed a roll-to-roll thin-film CIGS PV factory, at Hanwha where he directed global PV R&D activities, and at Applied Materials where he led the development and global implementation of SunFab technology. A pioneer in the development of efficient thin-film PV materials, he held high-level technology positions at Nanosolar, Unisun, and ARCO Solar / Siemens Solar Industries. Eberspacher earned a PhD in applied physics from Stanford University and a BS in physics from the University of Texas.

The pair founded Tandem PV (originally as Iris PV) in 2016 in order to develop tandem photovoltaic cells comprised of a metal-halide perovskite solar cell over a silicon-based cell. Tandem PV has raised nearly $1 million in grant funds and other support and is working toward commercial readiness with demonstrations of performance, durability, scalability, and cost.


Critical need: Improvements in the performance of solar panels are needed for solar power to become directly competitive with conventional sources of energy, especially as photovoltaic (PV) penetration grows.


Image credit: R. Jones-Albertus, M. Woodhouse, et al. Technology advances needed for photovoltaics to achieve widespread grid price parity”. Progress in Photovoltaics 2016.

Image credit: R. Jones-Albertus, M. Woodhouse, et al. Technology advances needed for photovoltaics to achieve widespread grid price parity”. Progress in Photovoltaics 2016.


Technology vision: By boosting the overall efficiency of conventional solar cells, Tandem PV will open new markets for residential and commercial photovoltaics, dramatically accelerating adoption worldwide.

Current state-of-the-art: Current solar panels use a single absorber material, limiting the performance of the panel. Double-junction tandems overcome this limitation by utilizing sunlight more effectively.

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Key innovation: Solution-processed metal-halide perovskites that are transparent to infrared light, stable, and low-cost.

Manufacturing challenges: Deposition and patterning of the perovskite at module scale with high yield and uniformity.

Competing technology: Tandem PV’s solar panels must surpass, at minimum, the performance of standard solar panels using silicon, CdTe, or CIGS. There is a strong likelihood that others will also attempt to make tandem solar cell products.

First market hypothesis: Initial entry will be in markets where performance is valued at a premium.

Potential for impact: The cost and performance improvements expected by Tandem PV’s technology will enable substantially higher PV penetration worldwide, potentially offsetting 3 Gigatons CO2eq per year. We will add large margins back to the income statements of PV companies and reinvigorate an increasingly choked industry.

We're looking for: 

  • Technical collaborators
  • Technoeconomic analysis 
  • Team members - scientists, engineers
  • Funders
  • Joint development partners









cdbailie [at] irispv [dot] com


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