Self-assembled monolayer achieves 31.1% efficiency

Researchers from Zhejiang University in China have developed a perovskite-TOPCon tandem solar cell with a top inverted perovskite cell incorporating a self-assembled monolayer (SAM) . This SAM enhances the thermal stability of the cell and optimizes energy alignment at the interface between the SAM and the perovskite layer. The tandem cell achieved a certified efficiency of 30.9% and an internally measured efficiency of 31.1% , with a high fill factor of 82.6% , an open-circuit voltage of 1.88 V , and a short-circuit current of 20.0 mA/cm² . The top perovskite cell demonstrated a power conversion efficiency of 22.8% and retained over 99% of its initial efficiency after 400 hours of maximum power point tracking at 60°C. The researchers believe this approach, leveraging SAMs and the inductive effect, could pave the way for the commercialization of high-efficiency, stable perovskite-based solar cells.

Data Extracted:

Device Structure:

1. Tandem Solar Cell Configuration:

   • Top cell: Perovskite cell (inverted "p-i-n" structure)

   • Bottom cell: TOPCon solar cell

2. Top Perovskite Cell Layers:

   • Transparent conductive oxide: Indium tin oxide (ITO)

   • Self-assembled monolayer (SAM): Modulates interfacial energetics

   • Hole transport layer: Nickel oxide (NiO)

   • Perovskite absorber: Wide-bandgap material with 1.68 eV energy bandgap

   • Electron transport layer (ETL): Composed of buckminsterfullerene (C60) and tin oxide (SnO2)

   • Transparent back contact: Indium zinc oxide (IZO)

   • Metal contact: Silver (Ag)

3. Bottom TOPCon Cell:

   • Standard silicon-based TOPCon solar cell

Performance Metrics:

1. Top Perovskite Cell:

   • Power Conversion Efficiency (PCE ): 22.8%

   • Open-Circuit Voltage (Voc ): 1.24 V

   • Fill Factor (FF ): 84.3%

   • Stability: Retained >99% of initial efficiency after 400 h at 60°C

2. Tandem Device (1 cm²):

   • Internally Measured Efficiency: 31.1%

   • Certified Efficiency: 30.9% (verified by Chengdu Institute of Product Quality Inspection Co., Ltd.)

   • Open-Circuit Voltage (Voc ): 1.88 V

   • Short-Circuit Current (Jsc ): 20.0 mA/cm²

   • Fill Factor (FF ): 82.6%

Key Features:

1. Self-Assembled Monolayer (SAM):

   • Modulates electron density to optimize interfacial energetics between the SAM and the perovskite layer.

   • Enhances thermal stability without affecting phase stability of the wide-bandgap perovskite film.

2. Inverted Perovskite Cell ("p-i-n" Structure):

   • Illuminated through the hole-transport layer (HTL).

   • Offers improved energy alignment and stability compared to conventional "n-i-p" structures.

3. High Fill Factor:

   • Both the top perovskite cell (84.3% ) and the tandem device (82.6% ) achieved high fill factors, indicating efficient charge extraction and low resistive losses.

4. Wide-Bandgap Perovskite Material:

   • Bandgap: 1.68 eV

   • Enables efficient light absorption and energy transfer in tandem configurations.

Applications and Implications:

1. Commercialization Potential:

   • The use of SAMs and the inductive effect strategy offers a promising path toward the commercialization of perovskite and perovskite-TOPCon tandem solar cells.

2. Stability Improvements:

   • Enhanced thermal stability makes these cells suitable for real-world applications, addressing one of the major challenges of perovskite solar cells.

3. Efficiency Gains:

   • High efficiencies (31.1% ) demonstrate the potential of tandem solar cells to surpass the theoretical limits of single-junction devices.

Research Context:

1. Previous Work:

   • In July, Zhejiang University researchers developed an inverted perovskite solar cell based on a high-entropy hybrid perovskite material , improving both stability and efficiency.

2. Publication Details:

   • Paper Title: “Inductive effects in molecular contacts enable wide-bandgap perovskite cells for efficient perovskite/TOPCon tandems”

   • Published in: Nature Communications

   • Open Access: CC BY-NC-ND 4.0