Passivation of the TiO₂ Surface and Promotion of N719 Dye Anchoring with Poly(4-vinylpyridine) for Efficient and Stable Dye-Sensitized Solar Cells

Abstract

Dye-sensitized solar cells (DSSCs) have turned to be the most promising PV technology for indoor applications, for sustainable powering billions of IoT devices and wireless indoor sensors; DSSCs are aesthetic, cheap, and safe, and they display extremely high power conversion efficiencies (PCEs). In this study, poly­(4-vinylpyridine) (P4VP) of molecular weights (MW) ranging from 2.8 to 18.5k was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization and studied as a new co-adsorbent with N719 dye to produce efficient DSSCs. P4VP adsorbs on TiO2 via coordinative bonding to the Lewis acid centers of the titania. The adsorbed P4VP effectively hampers the back-electron recombination at the photoanode/electrolyte interface and promotes stronger covalent dye bonding. The simultaneous adsorption of P4VP with N719 allowed reaching a PCE of ca. 7.5% under 1 Sun and with almost half dye loading of the reference device. Sequential adsorption of the P4VP led to a noticeable increase of the strongly covalent bonded dye fraction making the electron injection to the titania more efficient and improving the photocurrent density. The effect of polymer MW, concentration, and adsorption sequence with the N719 on the photovoltaic performance of the DSSCs is discussed. For the first time ever, the efficient long-chain polymeric P4VP co-adsorbent rendered a device with as high PCE as 9% under 1 Sun illumination and 22.5% under indoor 1000 lx light. The PCE history under natural aging suggests that P4VP is a high-performing co-adsorbent, which allows fabrication of quite stable devices.

First application of benzotriazole as a dye additive to dye-sensitized solar cells: electrochemical device characterization

“…3 ) were fitted using a simplified equivalent circuit (Fig. 1 .SI) [ 11 , 27 – 29 ]. The resistance values of TiO 2 /Dye, BTAH interface ( R WE ), and Pt/Electrolyte with the chemical capacitance ( C μ ) were estimated in Table 2 .…”

“…Again, the steric effect is caused by benzene presence in a molecule, and also the N719 dye deaggregation, as the BTAH molecules might be positioning themselves between the dye molecules, rising up the charge separation and transportation in the semiconductor electrolyte interface. To 20 mg mL −1 of BTAH, despite amazing e and c presumably reduce the number of dye molecules anchored in TiO 2 surface, supplying less electron under solar energy incidence, supported by j sc value in Table 1 [ 4 , 11 ].…”

“…Suppressing the oxide-electrolyte recombination is one of the most studied ways to produce DSSC with improved photoelectrochemical parameters [ 11 ]. From this standpoint, many technologies have been used to reduce Reaction 2 : push–pull dyes [ 12 ], using mix oxides [ 13 , 14 ], and electrolyte additives [ 15 ].…”

“…From this standpoint, many technologies have been used to reduce Reaction 2 : push–pull dyes [ 12 ], using mix oxides [ 13 , 14 ], and electrolyte additives [ 15 ]. Recently, Rodrigues and co-workers, [ 11 ] applied the poly (4-vinyl pyridine), observing a TiO 2 surface passivation, able to suppress the back-electron recombination and increasing the current, even at low dye loading [ 16 , 17 ]. This related study shows that is possible to use organic additives in dye solar cells, such as benzotriazole (BTAH).…”

Dye‐Sensitized Solar Cells with Efficiency over 36% under Ambient Light Achieved by Cosensitized Tandem Structure

“…1.5) [13][14][15] and 15-22% (200 lux). [23,49] In the past few years, the application of organic dyes in DSSCs has received much attention as they are free from rare metal requirements and have the characteristics of adjustable adsorption due to their high molar extinction coefficient values. [6] The cells using single organic dyes have achieved PCEs of 10-13.6% (AM.…”