Static, Dynamic, Dielectric, and Magnetic Investigations on AnE-PVstat: PCBM Polymer Solar Cells under Open-Circuit Conditions

Abstract

We report on the enhancement in the efficiency of inverted polymer solar cells because of increased open-circuit voltage and short-circuit current by using an electron collecting an interfacial layer of an aluminum-doped zinc oxide (AZO). The efficiency of polymer solar cells comprising a bulk heterojunction photoactive film of an anthracene containing poly(p-aryleneethynylene)-alt-poly(p-arylenevinylene)/1-(3methoxycarbonyl)propyl-1-phenyl [6,6] and phenyl-C 60 -butyric acid methyl ester has increased from 3.6% to 4.6% from the standard to the inverted architecture with Al concentrations of 0.6%, respectively. After this concentration, the efficiency starts to decrease. The reasons for these results are discussed based on the AC electrical process and magnetoconductance (MC) measurements under open-circuit conditions at room temperature. The frequency ( f) dependence of the real part (Z′) and the imaginary part (Z′′) of the complex impedance with various Al concentrations at open-circuit conditions at room temperature show three f regimes: low, mid, and high f. The Cole−Cole plots (Z′′ vs Z′) demonstrate an increase in the semicircle radius from the standard to the inverted architectures for Al concentrations of 0.2% and 0.6%, respectively. After this concentration (0.6%), the semicircle radius starts to decrease. Afterward, the present proposed impedance model shows some important physical parameters such as electron diffusion time (τ diff ), the recombination time (τ rec ), the diffusion constant (D n ), the diffusion length (L n ), and the electron mobility (μ n ). From the dielectric measurements, all devices have a unique relaxation process, which is the property of the Debye relaxation mechanism. Moreover, the dielectric constant (ε′) showed a strong dependence on f and the type of architecture. In addition, the dielectric loss (ε″) decreased significantly with f, and as a result, it has sparked a lot of interest in these materials' possible uses in electrical energy storage. The dielectric loss tangent (tan(δ))) peaks shifted a little bit toward higher f from the standard to the inverted structures, indicating reduction of relaxation time. Furthermore, we found an MC memory effect in the inverted cells. Then the mechanism responsible for the MC was determined with the current density versus the applied voltage in the log−log scale for the different elaborated cells at V OC . The results suggested that the applied voltage (V OC ) corresponds to the trapped charge limited current (TCLC) regime, with traps acting as recombination centers for electron−hole (e−h) pairs, preventing the formation of double carriers MC. For this reason, the MC in the device may be described using a stochastic Liouville equation in the context of the e−h pair model.

Effect of External Magnetic Field on Bulk Heterojunction Polymer Solar Cells

“…[12] Fe 3 O 4 @ZnO core-shell nanoparticles were also applied to boost the PCEs of PSCs. [13] However, the effect of the EMF on the PSCs based on the PTB7-DT:PC 71 BM BHJ composites incorporated with MNPs was not reported so far. [14] In this study, we investigate the effect of the Fe 3 O 4 MNPs aligned by the EMF within the PTB7-DT:PC 71 BM BHJ composite thin film.…”

“…[ 4–7 ] Various approaches have been attempted to realize efficient PSCs, [ 4–9 ] but the utilization of both magnetic nanoparticles (MNPs) and external magnetic field (EMF) to boost PCEs of the PTB7‐DT‐based BHJ PSCs was less reported. [ 10–13 ]…”

“…[ 12 ] Fe 3 O 4 @ZnO core–shell nanoparticles were also applied to boost the PCEs of PSCs. [ 13 ] However, the effect of the EMF on the PSCs based on the PTB7‐DT:PC 71 BM BHJ composites incorporated with MNPs was not reported so far. [ 14 ]…”

“…[4][5][6][7] Various approaches have been attempted to realize efficient PSCs, [4][5][6][7][8][9] but the utilization of both magnetic nanoparticles (MNPs) and external magnetic field (EMF) to boost PCEs of the PTB7-DT-based BHJ PSCs was less reported. [10][11][12][13] In the past years, both MNPs and EMF have drawn great attention in both academic and industrial sectors. [14] Iron oxide (II, III) (Fe 3 O 4 ) is one of the most commonly used MNPs because of its well-crystallinity, good thermodynamic stability, and more importantly, the outstanding superparamagnetic behavior.…”

Suppressing charge recombination in disordered polymers blend medium

“…Moreover, the low carrier mobilities of the conducting polymers and the short lifetime of the exciton restrict the active layer thickness below 200 nm, so it is not possible to boost optical absorption by merely increasing the thickness [8][9][10][11][12][13][14]. Thus, in addition to the absorber layer composition and device architecture, the PCE in TFPSCs depends on the augmentation of the open-circuit voltage and the fill factor (FF) [15][16][17].…”