## Abstract

Smart windows may incorporate integrated stacks of photovoltaic and electrochromic devices, whose opacity/transparency can be synergistically modulated (and/or wirelessly controlled) by autonomously generated voltages. This article demonstrates a proof of concept of an Internet of Things (IoT)-enabled system comprised of an integrated bulk (organic) heterojunction photovoltaic device with an (inorganic) electrochromic device. First, fully organic (poly[N-9’-heptadecanyl-2,7-carbazole-alt-5,5-(4’,7’-di-2-thienyl-2’,1’,3’-benzothiadiazole)]:phenyl-C71-butyric-acid-methyl) photovoltaic devices were fabricated, and their performance were evaluated with respect to optical transparency and power conversion efficiency (PCE). Upon varying the hole transport layers and substrates, the strongest performing devices exhibited a PCE of 3.2%, an open-circuit voltage (<inline-formula><tex-math notation="LaTeX">$V_{\text{oc}}$</tex-math></inline-formula>) of 0.9 V, and a short-circuit current (<inline-formula><tex-math notation="LaTeX">$J_{\text{sc}}$</tex-math></inline-formula>) of 10–15 mA/cm<inline-formula><tex-math notation="LaTeX">$^{2}$</tex-math></inline-formula>. Second, tungsten trioxide WO<inline-formula><tex-math notation="LaTeX">$_{3}$</tex-math></inline-formula> electrochromic films were inkjet printed on conductive and transparent ITO-coated PET substrates of varying mechanical flexibility, including PDMS with a network of embedded Ag nanowires and indium-tin-oxide-coated polyethylene terephthalate. The printed electrochromic devices demonstrated clear switching behavior under external bias, with a coloration time of 8 s, a bleaching time of 12 s, and an optical modulation of 0.5874 at <inline-formula><tex-math notation="LaTeX">$\lambda$</tex-math></inline-formula> = 525 nm. Finally, the photovoltaic and electrochromic devices were connected, with a network configuration of the former to provide requisite autonomous power for the demonstration of opacity modulation (or light transmission properties) of the latter, utilizing a Particle IoT controller that was switched wirelessly with a smartphone.

Original language | English (US) |
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Pages (from-to) | 1-6 |

Number of pages | 6 |

Journal | IEEE Journal of Photovoltaics |

DOIs | |

State | Accepted/In press - 2022 |

## Keywords

- Autonomous smart window
- Electrochromic devices
- Internet of Things (IoT)
- Nanoparticles
- Optical switches
- Performance evaluation
- Photovoltaic cells
- Photovoltaic systems
- Substrates
- electrochromics
- organic photovoltaics (OPV)

## ASJC Scopus subject areas

- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering