Solar Energy, Vol.188, 1189-1200, 2019
Switching on optical properties of D-pi-A DSSC sensitizers from pi-spacers towards machine learning
Organic photovoltaic (OPV) solar cells recently achieved a reported efficiency as high as 17.3%. In this study we explore new avenues of shifting the light absorber through rational design of the pi-spacers in the Donor-pi-spacer-Acceptor dyes. That is, to construct high performing new dyes with fixed donor (DCPA) and acceptor (PMID) from appropriate pi-building units of fluorene, EDOT and thiophene. These three pi-units form various combinations of the pi-conjugate spacers for new dyes. We focus on the development of the relationship between the three building units of pi-spacers to construct new DCPA-pi-spacer-PMID dyes and their UV-vis spectra in tetrahydrofuran (THF) solution. The latter (i.e., UV-vis spectra) are calculated using quantum mechanical time dependent density functional theory (TD-DFT) methods. This set of nine new organic dyes has been employed to develop augmented intelligence (AI). We discovered that repeating the fluorene (pi O) unit alone in the pi-spacer, such as OP100, OP200 and OP300 dyes, will lead to hyperchromic enhancement of the donor spectral band in the UV region of ca. 300 nm, with limited impact on the major spectral band at 500 nm which is stemmed from the acceptor (PMID). To maximize the UV-vis absorption, more efficient pi-spacers for this class of dyes are constructed from mixtures of the fluorene (pi O) and EDOT (pi P) units, such as pi O-pi P-pi O (OP210) or as pi O-pi P-pi O-pi P (OP220). The information obtained is useful to elucidate new dyes with desired properties with appropriate UV-vis spectra for future machine learning (ML).
Keywords:Organic photovoltaic (OPV) cells;Donor - pi-spacer - Acceptor structure;Impact of pi-spacer;Structure-property relationship;UV-vis absorption spectrum;TD-DFT calculations;Augmented intelligence (AI)