Bifacial dye-sensitized solar cells utilizing green-colored NIR sensitive unsymmetrical squaraine dye

Abstract

Dye-sensitized solar cells (DSSCs) with the capability of photon harvesting from both front and rear sides, consisting of newly developed NIR dye (SQ-140), iodine-based redox electrolyte, and transparent counter electrode with high bifaciality factor (BFF) and good cumulated photoconversion efficiency (PCE), are successfully fabricated and characterized. The use of transparent TiO2-based photoanode leads to improved BFF as compared to its opaque TiO2 counterparts: from 74% to 86% under similar experimental conditions and device parameters. The high molar extinction coefficient of the NIR dye SQ-140, needing a thinner TiO2 layer, was found to be advantageous to maintaining the high BFF even in thicker TiO2 films without serious compromise in the PCE. The lower efficiency of the bifacial DSSC under rear illumination was attributed to the hampered optical penetration as well as absorption of light by the intense colored iodine-based redox electrolyte.

Fabrication and Characterization of Bifacial Dye‐Sensitized Solar Cells Utilizing Indoline Dye with Iodine‐ and Cobalt‐Based Redox Electrolytes

“…Although the demonstration of DSSCs as BFSCs has already been carried out, leading to the enhancement of the overall PCE and improving the BFF, their lower BFF compared to silicon‐based BFSCs has limited their practical applications. [ 18 ] One of the possible reasons for the hampered BFF of the BF‐DSSCs is the absorption of light by the electrolyte itself, especially under backside light illumination. This self‐light trapping by the electrolyte in BF‐DSSCs can be prevented by utilizing cobalt‐complex‐based redox electrolytes owing to their relatively higher transparency as they are less colored than most commonly used iodine‐based redox electrolyte counterparts.…”

Bifacial Dye-Sensitized Solar Cells Utilizing Visible and NIR Dyes: Implications of Dye Adsorption Behaviour

“…These solar cells solve solar tracking problems efficiently by harvesting photons from both sides, demonstrating improved solar energy harvesting in a day [ 6 ]. The performance of these solar cells is assessed by their figures of merit, such as the bifaciality factor (BFF) and cumulative PCE [ 7 ]. Silicon-based bifacial solar cells have already achieved PCEs of 17–24% and BFFs ranging from 74% to 89% [ 8 ].…”