High-Efficiency Nonfullerene Organic Solar Cells with a Parallel Tandem Configuration

Lijian Zuo; Jiangsheng Yu; Xueliang Shi; Francis Lin; Weihua Tang; Alex K-Y Jen

doi:10.1002/adma.201702547

High-Efficiency Nonfullerene Organic Solar Cells with a Parallel Tandem Configuration

Adv Mater. 2017 Sep;29(34). doi: 10.1002/adma.201702547. Epub 2017 Jul 10.

Authors

Lijian Zuo¹, Jiangsheng Yu^{1

2}, Xueliang Shi¹, Francis Lin¹, Weihua Tang², Alex K-Y Jen^{1

3}

Affiliations

¹ Department of Materials Science and Engineering, University of Washington, Seattle, WA, 98195, USA.
² Key Laboratory of Soft Chemistry and Functional Materials, Nanjing University of Science and Technology, Nanjing, 210094, P. R. China.
³ Department of Materials Science and Engineering, and Department of Chemistry, City University of Hong Kong, Kowloon, HK, 999077, P. R. China.

PMID: 28692752
DOI: 10.1002/adma.201702547

Abstract

In this work, a highly efficient parallel connected tandem solar cell utilizing a nonfullerene acceptor is demonstrated. Guided by optical simulation, each of the active layer thicknesses of subcells are tuned to maximize its light trapping without spending intense effort to match photocurrent. Interestingly, a strong optical microcavity with dual oscillation centers is formed in a back subcell, which further enhances light absorption. The parallel tandem device shows an improved photon-to-electron response over the range between 450 and 800 nm, and a high short-circuit current density (J _SC ) of 17.92 mA cm^-2 . In addition, the subcells show high fill factors due to reduced recombination loss under diluted light intensity. These merits enable an overall power conversion efficiency (PCE) of >10% for this tandem cell, which represents a ≈15% enhancement compared to the optimal single-junction device. Further application of the designed parallel tandem configuration to more efficient single-junction cells enable a PCE of >11%, which is the highest efficiency among all parallel connected organic solar cells (OSCs). This work stresses the importance of employing a parallel tandem configuration for achieving efficient light harvesting in nonfullerene-based OSCs. It provides a useful strategy for exploring the ultimate performance of organic solar cells.

Keywords: light trapping; nonfullerenes; organic solar cells; parallel; tandem cells.