Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) has been mostly used as a counter electrode to give a high performance of dye-sensitized solar cell (DSSC). Recently, PEDOT doped by carrageenan, namely PEDOT:Carrageenan, was introduced as a new material to be applied on DSSC as an electrolyte. PEDOT:Carrageenan has a similar synthesis process as PEDOT:PSS, owing to their similar ester sulphate (-SO₃H) groups in both PSS and carrageenan. This review provides an overview of the different roles between PEDOT:PSS as a counter electrode and PEDOT:Carrageenan as an electrolyte for DSSC applications. The synthesis process and characteristics of PEDOT:PSS and PEDOT:Carrageenan were also described in this review. In conclusion, we found that the primary role of PEDOT:PSS as a counter electrode is to transfer electrons back to cell and accelerate redox reaction with its superior electrical conductivity and high electrocatalytic activity. PEDOT:Carrageenan as an electrolyte has not shown the main role for regenerating the dye sensitized at the oxidized state, probably due to its low ionic conductivity. Therefore, PEDOT:Carrageenan still obtained a low performance of DSSC. Additionally, the future perspective and challenges of using PEDOT:Carrageenan as both electrolyte and counter electrode are described in detail.

Poly(3,4-ethylenedioxythiophene) (PEDOT) with a dopant of polystyrene sulfonate (PSS), namely PEDOT:PSS, has been mostly used as counter electrode to give a high performance of dye-sensitized solar cells (DSSCs). Recently, PEDOT doped by carrageenan (PEDOT:Carrageenan) was introduced as a new material to be applied on DSSC as electrolyte. PEDOT:Carrageenan has a similar synthesis process as PEDOT:PSS owing to their similar ester sulphate (-SO3H) groups in both PSS and carrageenan. This review provides an overview of the different roles between PEDOT:PSS as counter electrode and PEDOT:Carrageenan as electrolyte for DSSC applications. The synthesis process and characteristics of PEDOT:PSS and PEDOT:Carrageenan were also described in this review. In conclusion, we found that PEDOT:PSS as counter electrode has the main roles of transferring electrons from the external circuit and accelerating the reduction reaction of redox coupled with its high electrical conductivity and high electrocatalytic activity. As electrolyte, PEDOT:Carrageenan has not shown the main role as an electron transfer from counter electrode to regenerate the dye-sensitized at the oxidized state due to its low ionic conductivity. Therefore, PEDOT:Carrageenan still obtained a low performance of DSSCs. Additionally, the future perspective and challenges of using PEDOT:Carrageenan as both electrolyte and counter electrode are described in detail.

TiO₂ are usually used as photoanode to get high-performance dye-sensitized solar cells (DSSCs). TiO₂ has good chemical stability, but still has poor electron mobility so that the DSSC efficiency is low. An alternative semiconductor metal-oxides such as ZnO currently are being explored due to ease of processing, higher electron mobility, interface band energetics, and can be utilized as photoanode also, but the chemical stability is low. Based on these facts, by combining the advantages of TiO₂ and ZnO, the TiO₂:ZnO composite can be an ideal material as a photoanode in DSSC. In this study, composite of TiO₂:ZnO was synthesized using sol-gel method with ratio of TiO₂ to ZnO were varied from 80:20, 60:40, 50:50, 40:60, and 20:80 in atomic percent. DSSCs were fabricated by coating the photoanode using screen-printing technique on a FTO-glass substrate. Composite of TiO₂:ZnO photoanodes were then sensitized in a solution of N719 dye for several hours. Finally, the DSSCs were assembled and the power conversion efficiency was measured using an I–V measurement system. The highest power conversion efficiency of 2.30% was obtained from the cell fabricated with TiO₂:ZnO (50:50) photoanode. This result indicated that the balanced composition allowed to increase J_sc along with reducing recombination process and retaining high dye-loading capability.

ZnO nanostructures show a wide range of applications as active materials in optoelectronic devices. The unique structures in 1-dimensional (1D) in combination with other potential materials (such as graphene-based) can increase several device performances. This research aims to observe the influence of an additional electric field (induced by different voltages of ±1 kV) during the growing process of the zinc oxide (ZnO): graphene oxide (GO) crystal. The ZnO:GO layers were prepared via the self-assembly method in 2 steps; the first was seed layer preparation by dip coating technique using Zn (CH3COO)2.2H2O and 0.5 (wt%) of AlCl3 as precursor and dopant, respectively. Secondly, growing ZnO rods using Zn (NO3)2·6H2O as precursor, 0.5 (wt%) GO (dispersed in water) as dopant materials, and hexamethylenetetramine (HMTA) as complexing agent. Applying an external field during self-assembly accelerated the ZnO hexagonal wurtzite crystal formation in a vertical growth direction, increasing the aspect ratio (L/d) of ZnO:GO rods. The direction of the applied external field affected the structure and morphology of the ZnO rods, which relates to ions and seed layer surface polarity during the synthesis process. The addition of an external field during the growing process induced the orderly alignment of ZnO rods, controlling growth perpendicular to the basal plane. This research has a significant scientific impact, elucidating the methods to control the 1D morphology of the ZnO growing process, which is closely related to the surface polarity properties of a material.