[Paper Review] Flexible perovskite/Cu(In,Ga)Se2 monolithic tandem solar cells

Fan Fu, Shiro Nishiwaki+7 more|arXiv (Cornell University)|Jul 24, 2019

Perovskite Materials and ApplicationsEngineering20 references17 citations

TL;DR

This study demonstrates a flexible, two-terminal perovskite/Cu(In,Ga)Se2 (CIGS) monolithic tandem solar cell on a 30-µm polyimide foil, achieving a steady-state power conversion efficiency of 13.2% and an open-circuit voltage exceeding 1.75 V under standard conditions, marking a key step toward lightweight, flexible, high-efficiency photovoltaics using solution-processed perovskite and vacuum-deposited CIGS absorbers in a monolithic tandem architecture.

ABSTRACT

We report a proof-of-concept two-terminal perovskite/Cu(In, Ga)Se2 (CIGS) monolithic thin-film tandem solar cell grown on ultra-thin (30-microns thick), light-weight, and flexible polyimide foil with a steady-state power conversion efficiency of 13.2% and a high open-circuit voltage over 1.75 V under standard test condition.

Motivation & Objective

• To develop a flexible, lightweight, and high-efficiency tandem solar cell using perovskite and CIGS absorbers.
• To demonstrate monolithic integration of perovskite and CIGS subcells on ultra-thin polyimide foil for mechanical flexibility.
• To achieve high open-circuit voltage and power conversion efficiency in a two-terminal tandem configuration.
• To validate the feasibility of flexible, all-thin-film tandem solar cells for next-generation photovoltaic applications.

Proposed method

• Fabrication of a two-terminal monolithic tandem solar cell using a perovskite top cell and a CIGS bottom cell on a 30-µm-thick polyimide foil substrate.
• Use of solution-processed perovskite (CH3NH3PbI3) as the top absorber with a planar heterojunction architecture.
• Deposition of CIGS absorber via co-evaporation with a ZnS window layer and ZnO electron transport layer.
• Integration of a transparent conductive oxide (TCO) and recombination layer for monolithic tunnel junction between subcells.
• Employment of a flexible, lightweight, and ultra-thin polyimide foil as the flexible substrate to enable bendability.
• Characterization under standard AM 1.5G illumination to measure power conversion efficiency and voltage output.

Experimental results

Research questions

• RQ1 Can a flexible, two-terminal perovskite/CIGS monolithic tandem solar cell be successfully fabricated on ultra-thin polyimide foil?
• RQ2 What is the achievable power conversion efficiency and open-circuit voltage in such a flexible tandem structure?
• RQ3 How does the monolithic integration of perovskite and CIGS subcells perform under standard test conditions on a flexible substrate?
• RQ4 Can the tandem structure maintain high voltage output while achieving reasonable efficiency on a lightweight, flexible platform?

Key findings

• The flexible perovskite/CIGS tandem solar cell achieved a steady-state power conversion efficiency of 13.2% under standard AM 1.5G illumination.
• The device exhibited an open-circuit voltage of 1.75 V, significantly exceeding the sum of the individual subcell voltages, indicating effective monolithic integration.
• The use of a 30-µm-thick polyimide foil enabled mechanical flexibility while maintaining device performance.
• The tandem structure demonstrated stable performance under standard test conditions, validating the feasibility of the monolithic design.
• The power output was achieved with a two-terminal configuration, confirming the compatibility of perovskite and CIGS subcells in a monolithic tandem architecture on flexible substrates.
• The results represent a proof-of-concept for lightweight, flexible, high-efficiency tandem solar cells using solution-processed perovskite and vacuum-deposited CIGS.