Color-neutral, semitransparent organic photovoltaics for power window applications

Yongxi Li; Xia Guo; Zhengxing Peng; Boning Qu; Hongping Yan; Harald Ade; Maojie Zhang; Stephen R. Forrest

doi:10.1073/pnas.2007799117

New Research In

Contributed by Stephen R. Forrest, July 1, 2020 (sent for review May 13, 2020; reviewed by Yonggang Huang and Jiangeng Xue)

Significance

We demonstrate a semitransparent organic photovoltaic cell that achieves a power conversion efficiency of 10.8% and visible transparency of ∼50% using a nonfullerene acceptor (NFA) featuring strong near-infrared (NIR) absorption and simple synthesis. Contrary to expectations, stronger NIR absorption and closer molecular packing are obtained by employing an additive in these partially, instead of fully fused, rigid NFAs. By combining NIR-absorbing material sets with an optical outcoupling structure as well as transparent electrode, we overcome the trade-offs between efficiency, transparency, and device appearance. These results surpass other semitransparent solar cell technologies based on organic and other thin-film materials systems, showing a promising future for ST-OPVs as power-generating windows and other solar energy harvesting applications.

Abstract

Semitransparent organic photovoltaic cells (ST-OPVs) are emerging as a solution for solar energy harvesting on building facades, rooftops, and windows. However, the trade-off between power-conversion efficiency (PCE) and the average photopic transmission (APT) in color-neutral devices limits their utility as attractive, power-generating windows. A color-neutral ST-OPV is demonstrated by using a transparent indium tin oxide (ITO) anode along with a narrow energy gap nonfullerene acceptor near-infrared (NIR) absorbing cell and outcoupling (OC) coatings on the exit surface. The device exhibits PCE = 8.1 ± 0.3% and APT = 43.3 ± 1.2% that combine to achieve a light-utilization efficiency of LUE = 3.5 ± 0.1%. Commission Internationale d’eclairage chromaticity coordinates of (0.38, 0.39), a color-rendering index of 86, and a correlated color temperature of 4,143 K are obtained for simulated AM1.5 illumination transmitted through the cell. Using an ultrathin metal anode in place of ITO, we demonstrate a slightly green-tinted ST-OPV with PCE = 10.8 ± 0.5% and APT = 45.7 ± 2.1% yielding LUE = 5.0 ± 0.3% These results indicate that ST-OPVs can combine both efficiency and color neutrality in a single device.

Footnotes

↵¹To whom correspondence may be addressed. Email: mjzhang{at}suda.edu.cn or stevefor{at}umich.edu.

Author contributions: Y.L. and S.R.F. designed research; Y.L., X.G., Z.P., B.Q., and H.Y. performed research; Y.L., X.G., Z.P., B.Q., H.Y., H.A., M.Z., and S.R.F. analyzed data; and Y.L., X.G., Z.P., B.Q., H.Y., H.A., M.Z., and S.R.F. wrote the paper.
Reviewers: Y.H., Northwestern University; and J.X., University of Florida.
Competing interest statement: S.R.F. has an ownership interest in one of the sponsors of this research, Universal Display Corp. This conflict is under management by the University of Michigan Office of Research.
This article contains supporting information online at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.2007799117/-/DCSupplemental.

Data Availability.

All study data are included in the article and SI Appendix, including cyclic voltammetry measurements, genetic algorithm calculations, and synthesis details.

Published under the PNAS license.

View Full Text