Aqueous p-type dye-sensitized solar cells based on a tris(1,2-diaminoethane)cobalt(ii)/(iii) redox mediator

Abstract

For the first time, we report the assembly of p-type dye-sensitized solar cells (pDSCs) based on an aqueous electrolyte containing a tris(1,2-diaminoethane)cobalt(II/III) ([Co(en)₃]^2+/3+) redox couple. With exception of devices made with pH 8.15 electrolytes (η = 1.13%) constant energy conversion efficiencies close to 1.5% were achieved with all other electrolytes under simulated one sun illumination (AM 1.5 G), with the best cell achieving an efficiency of 1.6%. Even higher efficiencies (≥1.9%) were achieved at a lower light intensity indicating that mass transport may be limiting performance at higher light intensities. The drop in V_OC with increasing pH is compensated by improvements in the short circuit current and fill factor. Notably, the efficiencies reported here for electrolytes with pH > 9 are higher than those reported for the corresponding devices made with an organic electrolyte based on the same redox mediator.