Effect of electric field on the spray deposited poly (3,4-ethylenedioxythiophene): poly(styrenesulfonate) layer and its use in organic solar cell

Abstract

Spray process under different applied voltages (0 V to 700 V) is used for the deposition of poly (3, 4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS) hole transport layer (HTL). The deposition of PEDOT:PSS film by spray process under the effect of electric field results in smoother film morphology, increase in conductivity and reduction in the sheet resistance. The improvement in surface morphology and conductivity enhancement of PEDOT: PSS films are the key to the improvement in the J–V characteristics of ITO/PEDOT:PSS/P3HT:PCBM/Al solar cell structures. The XPS peak height for PEDOT at 164.4 eV increased by 47% and that for PSS at 169.0 eV decreased by 30%, showing that the enhancement in the conductivity of the films deposited under electric field is due to the change in the PEDOT: PSS ratio. The organic solar cell using the electric field (created using 700 V) assisted spray deposited PEDOT:PSS film exhibit 42% and 69% improvement in the short circuit current density(Jsc) and power conversion efficiency, respectively, in comparison to the cells having PEDOT:PSS films deposited without the electric field.

Effect of high voltage electric field on structure and property of PEDOT : PSS film

“…In other words, the electric field did not change the chemical structure of the PEDOT : PSS film. This differs from the result from Dutta et al [29]. They applied a direct current electric field (75−175 kV/m) next to the nozzle which sprayed the solution and found that the band between 1400 and 1500 cm −1 became narrower and red-shifted, which indicated that the thiophene ring present in PEDOT : PSS was enhanced by structural transformation from benzeniod structure to quinoid structure.…”

“…The higher the electric field, the larger the roughness of the PEDOT : PSS film. On the contrary, Dutta et al [29] reported that the electric field decreased the film surface roughness significantly. For polar polymer molecule, non-superposition of cation and anion centers creates an electric dipole moment.…”

The effects of solvent treated PEDOT:PSS buffer layer in organic solar cells

“…Another vibrational mode of PEDOT:PSS assigned to C-C stretching is also observed around 1400cm -1 and around 1520cm -1 while the vibrational mode of PSS is located around 1550 cm -1 [30][31][32]. The Raman shift in the PEDOT vibrational mode indicating a conformation of the PEDOT changes from coil conformation to linear conformation after the treatment [33]. The partial removal of PSS is observed by the reduction in intensity of the Raman fingerprints [34].…”

“…The partial removal of PSS is observed by the reduction in intensity of the Raman fingerprints [34]. If the polymer chains have linear orientation where the neighboring thiophene rings are mostly oriented in the same plane, therefore the conjugated π-electrons should be delocalized over the whole polymer chain resulting in higher charge-carrier mobility as compared to coil structure [33]. Therefore, the interaction between PEDOT chains becomes stronger and can enhance the intra-chain and interchain charge-carrier mobility, so that the conductivity gets increased as discussed before.…”

Microstructure modulation of the CH3NH3PbI3 layer in perovskite solar cells by 2-propanol pre-wetting and annealing in a spray-assisted solution process

“…11 And it has also been used to prepare various of functional thin film materials, such as CdTe, 11 Bi 2 S 3 , 12 CuInS 2 13 and so on. In addition, this method was also widely used in the organic photovoltaic, such as spray deposition the active layer, 14,15 holetransport layer, 16 top electrode layer 17 and solvent spray annealing process. 18 Recently, some literatures have reported the deposition of perovskite films using ultrasonic spray-coating 19 or a simple spray gun 20,21 , but the average PCE of solar cells is at relative lower value, only about 10% due to smaller grain, more grain boundary and the larger the surface roughness etc.…”