The use of low-frequency current fluctuations in measuring the mobility of holes in the MEH-PPV polymer

• Published in: Synthetic metals 2024-12, Vol.309, p.117764, Article 117764
• Main Authors: Toušek, Jiří, Toušková, Jana, Křivka, Ivo, Ghasemi, Bita, Kuřitka, Ivo, Urbánek, Pavel
• Format: Article
• Language: English
• Subjects: Lifetime; Low-frequency fluctuations; MEH-PPV; Mobility; TCSPC method
• ISSN: 0379-6779
• DOI: 10.1016/j.synthmet.2024.117764

A diagnostic method based on the evaluation of low-frequency current fluctuation spectra is presented. When measuring the current through a p-type MEH-PPV sample, the occurrence of fluctuation is observable which can be measured with an AC amplifier. A model has been proposed that proves that the fluctuations originate from the interaction between the valence band and the band gap traps. The mean value of the amplitudes of these fluctuations increases linearly with decreasing frequency with a slope from which the product of mobility and lifetime of current carriers µpτp= (9 ± 3) × 10−15 cm2V−1 was obtained. The hole lifetime of (0.27 ± 0.01) ns was evaluated from the luminescence relaxation using the time-correlated single photon counting (TCSPC) technique. The mobility value (3 ± 1) × 10−5 cm2 V−1s−1 calculated using the above methods was compared with the mobility 1.8 × 10−5 cm2 V−1s−1 determined by the CELIV method (Charge extraction by linearly increasing voltage) and good agreement was obtained. [Display omitted] •A new method for determining the mobility of charge carriers.•Low – frequency 1/f fluctuations in MEH-PPV polymer.•The fluctuations originate from the interaction of the traps and the valence band.•Fluctuations along with relaxation of luminescence give mobility.