Correlation between density of paramagnetic centers and photovoltaic degradation in polythiophene-fullerene bulk heterojunction solar cells

Abstract

We investigated the physical processes underlying the degradation of poly(3-hexyl-thiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) photovoltaics under harsh environmental conditions during a 70-70-70 test (70% humidity at 70 °C from 0 to 70 h) using a variety of analytical techniques aimed at monitoring moisture incorporation. While the total oxygen content did not significantly increase during the test, a limited fraction of oxygen forms paramagnetic centers in P3HT, PCBM and, more limitedly, P3HT:PCBM heterojunctions. A strong correlation exists between the density of paramagnetic centers and the decay in the AM 1.5 photoconversion efficiency of the devices.

Impact of Synthetic Route on Photovoltaic Properties of Isoindigo‐Containing Conjugated Polymers

“…It was shown previously that ESR spectroscopy is a powerful tool for evaluating paramagnetic defects in semiconductor materials, for example, conjugated polymers. [ 31 ] The ESR signals for polymers P1‐B and P1‐Sn were recorded, and the concentrations of paramagnetic defects normalized by the sample mass ( C R ) were calculated (Figure 4d, Table 1). It was found out, that concentration of radical impurities in polymer P1‐B is more than five times higher compared to that for P1‐Sn .…”

Improved lifetimes of organic solar cells with solution‐processed molybdenum oxide anode‐modifying layers

“…Although various mechanisms are suggested for the degradation of organic solar cells , the presence of oxygen and moisture are believed to play a major role in the degradation of P3HT/PCBM BHJ devices with PEDOT/PSS as hole transport layer via photochemical reaction with either the fullerene or P3HT . Moreover, Bauld et al recently investigated the impact of oxygen and moisture in the active layer on device degradation using Rutherford backscattering and electron spin resonance. By measuring the induced oxygen content, which forms the paramagnetic defect centers that are associated with, the authors suggested that devices containing PEDOT/PSS are likely to possess higher densities of these defect centers.…”

“…Although various mechanisms are suggested for the degradation of organic solar cells [5,22,39], the presence of oxygen and moisture are believed to play a major role in the degradation of P3HT/PCBM BHJ devices with PEDOT/PSS as hole transport layer via photochemical reaction with either the fullerene [40] or P3HT [41]. Moreover, Bauld et al [42] recently investigated the Improved lifetimes of organic solar cells A. Garg et al impact of oxygen and moisture in the active layer on device degradation using Rutherford backscattering and electron spin resonance.…”

Tessellated gold nanostructures from Au144(SCH2CH2Ph)60 molecular precursors and their use in organic solar cell enhancement

“…Each of the solar cells were prepared using the fabrication procedure described in detail in ref. 20. Briey, an electronblocking, hole-transport layer consisting of a 30 nm Poly(3,4-Ethylene Di-Oxy-Thiophene):Poly-Styrene Sulfonate thin lm (PEDOT:PSS, Aldrich cat.…”