Color-neutral, semitransparent organic photovoltaics for power window applications

Area of Science:

• Materials Science
• Renewable Energy Engineering
• Optoelectronics

Background:

• Semitransparent organic photovoltaic cells (ST-OPVs) are promising for integrated solar energy harvesting in buildings.
• A key challenge is balancing power-conversion efficiency (PCE) with average photopic transmission (APT) for aesthetically pleasing, power-generating windows.

Purpose of the Study:

• To develop color-neutral ST-OPVs that achieve high PCE and APT.
• To explore the use of novel materials and device architectures to overcome the efficiency-transparency trade-off.

Main Methods:

• Fabrication of ST-OPVs using a transparent indium tin oxide (ITO) anode, a narrow energy gap nonfullerene acceptor near-infrared (NIR) absorbing cell, and outcoupling (OC) coatings.
• Characterization of device performance, including PCE, APT, and light-utilization efficiency (LUE).
• Evaluation of color properties using Commission Internationale d'eclairage (CIE) chromaticity coordinates, color-rendering index (CRI), and correlated color temperature (CCT).

Main Results:

• A color-neutral ST-OPV achieved PCE = 8.1 ± 0.3% and APT = 43.3 ± 1.2%, resulting in LUE = 3.5 ± 0.1%.
• The device exhibited favorable color properties with CIE coordinates (0.38, 0.39), CRI of 86, and CCT of 4,143 K under simulated AM1.5 illumination.
• An alternative device using an ultrathin metal anode demonstrated a slightly green-tinted ST-OPV with higher PCE = 10.8 ± 0.5% and APT = 45.7 ± 2.1%, yielding LUE = 5.0 ± 0.3%.

Conclusions:

• ST-OPVs can be engineered to achieve both high power conversion efficiency and color neutrality.
• The demonstrated devices represent a significant advancement towards practical applications of power-generating windows.