Use of Ultrafast Time-Resolved Spectroscopy to Demonstrate the Effect of Annealing on the Performance of P3HT:PCBM Solar Cells

Abstract

The organic solar cells of heterojunction system, ITO/PEDOT:PSS/P3HT:PCBM/Al, with a thermal annealing after deposition of Al exhibit better performance than those with an annealing process before deposition of Al. In this study, ultrafast time-resolved spectroscopy is employed to reveal the underlying mechanism of annealing effects on the performance of P3HT:PCBM solar cell devices. The analyses of all decomposed relaxation processes show that the postannealed devices exhibit an increase in charge transfer, in the number of separated polarons and a reduction in the amount of recombination between excited carriers. Moreover, the longer lifetime for the excited carriers in postannealed devices indicates it is more likely to be dissociated into photocarriers and result in a larger value for photocurrent, which demonstrates the physical mechanism for increased device performance.

Enhanced Charge Separation Efficiency in DNA Templated Polymer Solar Cells

“…The principal features one can observe in these maps are i) photoinduced absorption (positive Δ A ) in the region between 620 and 1300 nm which can be further divided into features PIA 1 to PIA 5 (see, for example, Figure a,c), and ii) photoinduced bleaching (negative Δ A ) in the wavelength region 470–620 nm (2.0–2.75 eV) which can be further divided into the features labeled PB 1 , PB 2 , and PB 3 as shown in Figure c–f. These features are common to the TA spectra of all blended P3HT polymers and we rely on the comprehensive literature to make an assignment of each of these features . The photoinduced bleaching in the visible region, PB 1 , PB 2 , and PB 3 which correspond reasonably well with the energies of the A 1 , A 2 , and A 3 transitions in the static UV–vis spectra discussed in the previous section, are generally assigned to ground state bleaching .…”

“…Ultrafast optical spectroscopy has been used extensively to determine the time scales and efficiencies of the above described processes in BHJ devices . The particular form of ultrafast spectroscopy used in this work is TA spectroscopy in which an optical pump excites the sample and a white light continuum probes the photoinduced effects at a variable delay time.…”

Universal route to optimal few- to single-cycle pulse generation in hollow-core fiber compressors

“…In particular, such pulses have paved the way for attosecond physics and metrology [1][2][3][4][5][6], via the extreme ultraviolet (XUV) attosecond pulse trains and isolated attosecond pulses [7] that can be obtained by high-harmonic generation (HHG). The use of few-cycle optical pulses with durations close to or shorter than 10 fs in the near-infrared, visible and near-ultraviolet spectral regions has been extended in recent years to a wide range of spectroscopic techniques such as impulsive vibrational spectroscopy [8][9][10], time-resolved stimulated Raman spectroscopy [11][12][13][14], and ultrafast pump-probe absorption spectroscopy [15,16]. Few-cycle optical pulses have also become an interesting tool for transient absorption microscopy [17], near-field imaging techniques [18] and for generating ultrashort terahertz radiation [19].…”

Development of Ultrashort Pulse Lasers for Ultrafast Spectroscopy

“…Thus, ultrafast electronic dynamics and vibrational dynamics can be studied simultaneously in the common experimental condition [32][33][34][35][36][37].…”