Understanding the role of the dye/oxide interface via SnO₂-based MK-2 dye-sensitized solar cells

Abstract

To understand the role of the dye/oxide interface, a model system using a nanocrystalline SnO2 and 3-hexyl thiophene based MK-2 dye is proposed. A thin interfacial TiO2 blocking layer (IBL) is introduced in between SnO2 and MK-2 and its effects on photocurrent-voltage, electron transport-recombination, and density of states (DOS) are systematically investigated. Compared to the bare SnO2 film, the insertion of IBL leads to a 14-fold improvement in the power conversion efficiency (PCE) despite little change in the dye adsorption amount, which is due to the 7-fold and 2-fold increase in the photocurrent density and voltage, respectively. The charge collection efficiency is substantially improved from 38% to 96% mainly due to the increase in the electron lifetime. The IBL is also found to enhance the dye regeneration efficiency as confirmed by the 15-fold faster dye bleaching recovery dynamics. The recombination resistance increases and the DOS decreases after surface modification of SnO2, which is responsible for the doubly increased voltage. This study suggests that the interfacial layer between the oxide and the dye plays a crucial role in retarding recombination, improving charge collection efficiency, increasing diffusion length, accelerating dye regeneration and narrowing the density of states.

SnO2 Transparent Printing Pastes from Powders for Photon Conversion in SnO2‐Based Dye‐Sensitized Solar Cells

“…MK2 is aw ell-known benchmark sensitizer for both TiO 2 and SnO 2 DSC devices, which is reported to result in a3 .1 %P CE with a9 .5 mA cm À2 J SC forh ydrothermally synthesized SnO 2 NPs. [11] Beginning from commerciallya vailableS nO 2 NPs and using the GSCM forp aste preparation, MK2 SnO 2 devices show an improvedPCE value of 4.1 %(Ta ble 1, Figure 7) with asignificantly higher J SC value than previously reported (14.7 vs. 9.5 mA cm À2 ). Thei ncrease in J SC is attributed to better photon management due to either fewer reflective losses or access to thicker SnO 2 films allowing for better light harvesting.…”

“…Two methods of SnO 2 paste preparation were analyzed based on either a simple sonication method (SM) or a grind, sonicate, and centrifuge method (GSCM, Figure ) . The SM approach is simpler and compared with a GSCM method using three sequential techniques for aggregate reduction …”

“…This provides an example of a dye which could inject more efficiently into the more positive SnO 2 CB. MK2 is selected as a benchmark organic dye which is known to perform well in TiO 2 and SnO 2 based DSC devices from prior studies which allows for analysis of the paste preparation methods used to make the photoanodes in this manuscript with other literature reports …”

Nanostructured Semiconductor Materials for Dye-Sensitized Solar Cells

“…Sufficient light absorption is achieved by the nanocrystalline form of the semiconductor, because a large internal surface area increases the dye concentration in the film per unit device area. Wide band gap MOSs ( > 3 eV) [57], such as TiO 2 [58][59][60], ZnO [61][62][63][64][65][66][67], SnO 2 [60,[68][69][70][71], and Nb 2 O 5 [72][73][74], have been studied more or less extensively and used as photoanode materials for DSSC devices. These MOSs present good stability against photocorrosion, transparency in the major part of the solar spectrum, and good electronic properties [75][76][77][78].…”

Efficient synthesis of triarylamine-based dyes for p-type dye-sensitized solar cells

“…While many different dyes have been tested with regard to their performance in p -type DSSCs 9 12 16 17 18 19 20 21 22 23 , only few systematic and mechanistic studies are available to date 8 10 18 19 24 25 26 27 28 29 30 31 32 33 34 . The (counterpart) n -type DSSC is an outstanding example for how systematic materials studies 3 4 35 and an increasing mechanistic understanding 36 37 38 have led to a successive improvement of efficiencies. Besides, design concepts which have been successfully applied in n -type DSSCs should be transferred to p -type DSSCs in order to improve their efficiency.…”