Colloidal Quantum Dot Tandem Solar Cells Using CVD Graphene as An Atomically Thin Intermediate Recombination Layer

TL;DR

This paper demonstrates a solution-processed two-terminal PbS quantum dot tandem solar cell utilizing CVD graphene as an atomically thin intermediate layer, achieving over 7% efficiency, surpassing previous CQD tandem cells.

Contribution

It introduces a novel tandem solar cell architecture with CVD graphene as the IML, improving efficiency in solution-processed PbS CQD devices.

Findings

Achieved over 7% power conversion efficiency.

Demonstrated effective use of CVD graphene as an IML.

Enhanced tandem cell performance compared to prior CQD devices.

Abstract

Two-terminal tandem cell architectures are believed to be an effective way to further improve the power conversion efficiency in solution processed photovoltaics. To design an efficient tandem solar cell, two key issues need to be considered. Firstly, subcells with well-matched currents and complementary absorption characteristics are a prerequisite for high efficiency. Secondly identifying the appropriate intermediate layer (IML) to connect the subcells is necessary to minimize the optical and electronic losses. PbS colloidal quantum dots (CQDs) are a notable choice for the subcells due to their low cost, solution processibility and remarkable wide range band gap tunability. Single layer Graphene (Gr) has been proposed to be a promising IML due to its high transparency and conductivity. Here, as a proof of concept, we demonstrate a solution processed two terminal PbS CQDs tandem solar cell employing chemical vapor deposited Gr as the IML. In doing so, we report a PbS CQD cell comprising subcells with bandgaps of 1.4 and 0.95 eV that delivers power conversion efficiency in excess of 7%, substantially higher than previously reported CQD tandem cells.