The Infinite Unknown

Summary

Tandem PV is a San Mateo, California-based photovoltaic technology company founded in 2021, specializing in perovskite-silicon tandem (multijunction) solar cells. The company develops photovoltaic devices that stack a wide-bandgap perovskite absorber layer on top of conventional crystalline silicon to create a tandem architecture. This stacked approach allows the perovskite layer to capture high-energy photons while the silicon layer captures lower-energy photons, theoretically enabling power conversion efficiencies of 30–35% — substantially higher than single-junction silicon’s ~22% practical limit. Tandem PV aims to achieve commercial-scale production of tandem cells by leveraging existing silicon manufacturing infrastructure while integrating perovskite layers through optimized processing.

Key Facts

• Founded: 2021
• HQ: San Mateo, CA
• Type: Private (venture-backed)
• Key investors / funding: Undisclosed specific amounts; backing includes venture capital and clean energy investors; Series funding rounds ongoing
• Core technology: Perovskite-on-silicon tandem solar cells — wide-bandgap halide perovskite layer laminated or monolithically integrated on crystalline silicon base
• Target efficiency: 30–35% at scale (lab record ~32% at small cell size; scaling to production remains challenge)
• Key differentiator: Leverages existing silicon supply chains and manufacturing know-how; compatible with silicon module assembly processes
• Production approach: Partnership-based model; targeting integration with established silicon wafer manufacturers and module assemblers
• Deployment status: Early pilot production and testing; commercial scale-up timeline targets 2025–2026
• Supply chain leverage: Silicon base can be manufactured using conventional crystalline silicon infrastructure; perovskite layer added in final processing steps

What It Is / How It Works

Tandem solar cell architecture: A tandem or multijunction solar cell combines two or more semiconductor materials with different bandgaps in a layered stack. Photons are selectively absorbed based on energy:

• Top layer (perovskite): Wide bandgap (~1.6–1.75 eV) absorbs photons from UV through green light (higher energy); lower-energy photons transmit through to the silicon layer
• Bottom layer (silicon): Narrow bandgap (~1.1 eV) absorbs the remaining lower-energy photons transmitted by the perovskite

Efficiency advantage: The Shockley-Queisser limit for a single-bandgap material (e.g., silicon alone) is ~29% under standard test conditions. By using two bandgaps in optimal combination, tandem cells can theoretically approach or exceed 35% depending on layer thickness, composition, and spectral tuning. In practice, efficiency gains of 5–8 percentage points over silicon alone are realistic for well-optimized designs.

Integration methods:

1. Monolithic tandem: Perovskite and silicon are directly connected by a tunneling junction, no additional substrates; highest current matching potential; most challenging to manufacture
2. Mechanically stacked (laminated): Perovskite cells are prepared separately on a transparent support and optically bonded to a silicon cell; simpler manufacturing; minor optical losses from interfaces

Perovskite material selection: Tandem PV likely uses formamidinium-cesium or methylammonium-cesium mixed-cation perovskites with halide composition (iodide/bromide mix) tuned to the ~1.6–1.75 eV target bandgap. Precise cation and halide ratios control bandgap and stability — a crucial material optimization lever.

Manufacturing integration: The perovskite layer is deposited (spin-coating, blade-coating, or vapor-phase deposition) onto or combined with silicon wafers in a final production step. This leverages the ~99% of silicon manufacturing already in place globally, adding a thin perovskite conversion layer — a manufacturing-friendly approach vs. building entirely new PV production lines.

Notable Developments

• 2023–2024: Focus on increasing cell-size efficiency and moving from lab-scale (cm²-scale test cells) to pilot-scale (30×30 cm and larger) prototypes; partnerships with established silicon module manufacturers for process integration studies.
• 2021: Tandem PV founded; team includes researchers from academic photovoltaics programs (Stanford, MIT, other institutions) with expertise in perovskite synthesis, device physics, and silicon integration.
• Ongoing: Perovskite material stability and degradation testing under accelerated lifecycle conditions; encapsulation strategies to prevent moisture ingress and ion migration.

Key People

Colin Bailie — Founder & Chief Technology Officer

• LinkedIn: Search “Colin Bailie Tandem PV”
• Background: PhD, Materials Science and Engineering (Stanford); BS, Mechanical Engineering (Texas A&M). Developed the first perovskite-silicon tandem solar cell during his doctoral research at Stanford — the foundational IP underpinning Tandem PV. Forbes 30 Under 30 (Energy). Activate fellow at Cyclotron Road (DOE startup accelerator). Leads Tandem PV’s perovskite materials science, device physics, and technology roadmap.

Chris Eberspacher — Co-Founder & Managing Director

• LinkedIn: Search “Chris Eberspacher Tandem PV”
• Background: 35+ years of solar industry experience. PhD, Applied Physics (Stanford); BS, Physics (University of Texas). Led thin-film CIGS solar cell development at ARCO Solar and Siemens Solar in the 1980s–2000s; co-founded Unisun (non-vacuum PV processes); senior roles at Nanosolar, Applied Materials, SoloPower Systems, and Hanwha Solar. Brings deep manufacturing and commercialization experience to Tandem PV’s silicon integration strategy.

Scott Wharton — Chief Executive Officer

• LinkedIn: Search “Scott Wharton Tandem PV”
• Background: Solar industry executive leading Tandem PV’s commercial strategy and utility-scale customer development. Has stated plans to have tandem solar panels ready for utility-scale customers by 2026.

Leadership — Last Reviewed: 2026-04-03

Supply Chain Position

⚑ Perovskite stability and longevity: The primary technical risk is perovskite material degradation under combined heat, humidity, and UV exposure. Perovskites naturally degrade faster than silicon in outdoor conditions; successful commercialization requires encapsulation and stabilization approaches that retain efficiency for 25–30 years (industry standard warranty). This remains an open research challenge.

⚑ Scaling monolithic tandem: Lab-scale monolithic tandems (small cells, <10 cm²) show promise; scaling to production-size cells (>200 cm²) introduces new manufacturing challenges (yield, uniformity, defect control). Mechanical stacking is simpler but adds optical losses (~3–5% efficiency penalty).

⚑ Silicon supply constraints (temporarily): Crystalline silicon wafer production is globally distributed and generally unconstrained. However, a rapid scale-up of tandem production (if commercialization is successful) could create localized supply tightness for specific wafer specifications.

Research Relevance

Why this matters for photovoltaics research: Tandem PV represents a critical next-generation efficiency milestone. Single-junction silicon has dominated commercial solar for 40+ years and has reached performance plateaus (~22–23% average, ~24% best-in-class). Tandem architectures offer:

1. Efficiency leap: A 30%+ tandem cell represents a ~30–40% improvement in power output per unit area vs. silicon alone — meaningful for land use (fewer acres needed for equivalent power) and balance-of-system costs (fewer frames, racking, inverters per MW).

2. Supply chain realism: Unlike competing multijunction approaches (III-V semiconductors used in space/CPV), perovskite-silicon tandem leverages the existing global silicon supply chain and manufacturing infrastructure — a critical advantage for rapid commercialization.

3. Cost trajectory: If tandem cells can be produced at cost parity with premium silicon cells (within ~20% cost premium), the efficiency gain alone creates economic advantage; further process optimization could reach cost parity.

4. Competition and technology lock-in: Early commercial success in tandem cells could fragment the solar manufacturing base (some players moving to tandem, others remaining silicon-only), creating supply and cost dynamics shifts.

The 2021 founding date positions Tandem PV early in a technology transition likely to define 2026–2030+ solar manufacturing.

Claim Verification

Claim: “Perovskite-silicon tandem cells can achieve 30%+ efficiency”

Status: Partially verified — lab demonstrations confirmed; commercial production has not yet been achieved

Supporting: Academic research (NREL, Fraunhofer ISE, MIT) has published certified perovskite-silicon tandem cell efficiencies of 29–32%; Tandem PV likely has comparable or better lab results (proprietary)

Limiting: Scaling from 1–2 cm² lab cells to 180+ cm² production cells introduces losses (series resistance, shunting, defects); full-size module efficiency will be lower than small-cell lab record. Realistic commercial efficiency likely 26–29% for first-generation production.

Summary: Lab performance is achievable and verified; commercial scale performance will be lower but still competitive.

Claim: “Tandem approach leverages existing silicon manufacturing”

Status: Verified in principle; execution remains uncertain

Supporting: Perovskite layer addition is designed as a post-wafer-processing step; existing silicon module assembly can be adapted with minimal capital investment for test runs

Limiting: Integrating perovskite deposition into a silicon module factory requires significant process validation, yield ramp, and worker training — not trivial at scale

Summary: The claim is technically sound but commercialization execution risk is real.

Sources

• Tandem PV — tandem-pv.com
• Perovskite-Silicon Tandem Solar Cells — NREL Research
• Fraunhofer ISE Perovskite Tandem Efficiency Records
• Photovoltaic Research Handbook — IEEE Spectrum