Suppression of back electron recombination on the photoanode-electrolyte interface with poly(4-vinylbenzoic acid) and poly(4-vinylpyridine) co-adsorbents for stable and efficient dye-sensitized solar cells

Abstract

Dye-sensitized solar cells (DSSC) are one of the most intensively developing PV technology to meet the emerging needs of wireless power for billions of IoT devices and wireless electronics; DSSCs have recently entered the indoor PV market. Suppressors of back electron recombination on the photoanode-electrolyte interface, also known as co-adsorbents, are key components of the DSSCs to obtain high power conversion efficiencies (PCE). Chenodeoxycholic acid (CDCA), yet obtained by extraction from the animal liver, dominates among other co-adsorbent and enables devices with the highest PCE and long lifetime. Achieving adequate PCE with long-term device stability with CDCA alternatives is a challenge addressed in this study using poly4-vinylbenzoic acid (PVBA) and poly(4-vinylpyridine) (P4VP). Polymeric co-adsorbents effectively suppress electron transfer from the TiO2/N719 photoanode to I3−/3I− electrolyte resulting in decently performing devices with 1-sun equivalent PCEs of 8.3 % and 9 %, respectively; 17.5 % and 22 % of artificial light PCEs were achieved. The presence of the polymer hampers molecular dye aggregation within the self-assembled monolayer; the acceleration of the charge injection and excited dye prolonging was monitored by Time-Correlated Single Photon Counting photoluminescence spectroscopy. Intrinsic device degradation in the accelerated light soaking test was assessed according to ISOS-L2 protocol. Carboxylic-functioned molecular chain of PVBA allows stronger adsorption on the photoanode-electrolyte interface and renderes stable devices with 1000 h of PCE history equivalent to conventional CDCA.