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

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 coadsorbent and enables devices with the highest PCE and long lifetime. Achieving adequate PCE with longterm 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 I-3(-) /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.