Introduction to Perovskite Tandem Lamination Process

Introduction to Perovskite Tandem Lamination Process

Perovskite tandem solar cells combine a wide-bandgap perovskite top subcell with a narrow-bandgap bottom subcell (typically silicon) to break the Shockley–Queisser limit of single-junction solar cells and achieve higher power conversion efficiency. Lamination is a key low-temperature, scalable integration route for fabricating perovskite tandem devices, alternative to direct deposition of perovskite onto pre-fabricated silicon cells.

1. Basic Principle of Lamination

Instead of sequentially depositing all functional layers of the top cell directly on the bottom cell, the perovskite top subcell and the silicon bottom subcell are pre-fabricated on separate substrates first. The two pre-made subcells are then aligned, bonded together under controlled temperature and pressure via an intermediate conductive adhesive/transparent conductive interlayer, forming a mechanically stacked tandem structure with electrical interconnection.

This approach avoids damage to the underlying silicon cell caused by the perovskite solution processing, thermal annealing, or solvent corrosion during direct deposition.

2. Main Process Flow

1. Pre-fabrication of individual subcells

• Perovskite top cell: Deposit transparent conductive electrode, hole transport layer, perovskite light-absorbing layer, electron transport layer and contact layer on a transparent carrier substrate (glass or flexible film).

• Silicon bottom cell: Prepare textured silicon cell with front/rear passivation layers and electrodes.

2. Surface treatmentClean and activate the bonding surfaces of both subcells to remove contaminants, reduce interface defects and optimize contact resistance.

3. Interlayer preparationApply a thin conductive, transparent lamination medium: conductive adhesive, thermoplastic conductive film, or transparent conductive composite. This layer provides electrical coupling and stress buffering.

4. Alignment and stackingPrecisely align the top and bottom subcells under an optical alignment system to match the active areas.

5. Thermo-compression laminationApply uniform pressure together with moderate heating inside a laminator or vacuum hot press. Vacuum environment is commonly used to eliminate air bubbles at the bonding interface. Temperature and pressure parameters are strictly controlled to prevent perovskite degradation.

6. Curing and post-treatmentCure the bonding medium if adhesive is used. Conduct edge isolation to prevent shunts.

7. CharacterizationTest the tandem device for J-V performance, electroluminescence, quantum efficiency, interface adhesion and stability.

3. Key Advantages

• Low-temperature compatibility: Most lamination processes run below 150 °C, compatible with heat-sensitive perovskite materials.

• Independent optimization: The perovskite top cell and silicon bottom cell can be separately optimized, which simplifies process development.

• Reduced compatibility risk: Eliminates solvent and annealing damage to the bottom cell.

• Good potential for roll-to-roll manufacturing for flexible tandem modules.

4. Main Challenges

• Interface contact resistance: Poor contact between subcells introduces series resistance and efficiency loss.

• Optical loss: The lamination interlayer may cause parasitic absorption and reflection.

• Uniformity and bubble defects: Inhomogeneous pressure or trapped bubbles lead to local failure.

• Long-term stability: Thermal cycling and moisture ingress may weaken the bonding interface and trigger delamination.

• Precision alignment requirement: High alignment accuracy is required for large-area modules.

5. Brief Comparison with Direct Deposition Tandem

Direct deposition grows perovskite stack directly on silicon; it features intimate optical and electrical contact but faces severe solvent and thermal incompatibility. Lamination is a mechanical stacking method with looser process compatibility, yet extra optical and resistive losses from the bonding interface need to be managed.

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