title: Photocurrent generation in organic photodetectors with tailor-made active layers fabricated by layer-by-layer deposition.
abstract: Photodetectors supply an electric response when illuminated. The detectors in this study consist of an active layer and a polyvinylidene fluoride (PVDF) blocking layer, which are sandwiched by an aluminum and an indium tin oxide (ITO) electrode. The active layer was prepared of Zn porphyrins and assembled by covalent layer-by-layer (LbL) deposition. Layer growth was monitored by UV-vis absorbance, ellipsometry, and X-ray photoelectron spectroscopy. Upon exposure to chopped light, the detectors show an alternating transient photocurrent, which is limited by the accumulation of space charges at the blocking layer/active layer interface. We could show that the number of photoactive layers has a significant impact on device performance. The fastest response was achieved with fewer layers. The highest photocurrents were measured for detectors with an intermediate number of layers, beyond which, more layers did not lead to an increase in the photocurrent despite containing more active material.
authors: †Department of Chemistry and Research Centre for Materials Science, Nagoya University, Furo-cho, Chikusa, 464-8602 Nagoya, Japan.|‡Organic Chemistry Institute, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, 48149 Münster, Germany.
authors: Benjamin
authors: B
authors: Vonhoeren
authors: †Department of Chemistry and Research Centre for Materials Science, Nagoya University, Furo-cho, Chikusa, 464-8602 Nagoya, Japan.
authors: Simon
authors: S
authors: Dalgleish
authors: †Department of Chemistry and Research Centre for Materials Science, Nagoya University, Furo-cho, Chikusa, 464-8602 Nagoya, Japan.
authors: Laigui
authors: L
authors: Hu
authors: †Department of Chemistry and Research Centre for Materials Science, Nagoya University, Furo-cho, Chikusa, 464-8602 Nagoya, Japan.
authors: Michio M
authors: MM
authors: Matsushita
authors: †Department of Chemistry and Research Centre for Materials Science, Nagoya University, Furo-cho, Chikusa, 464-8602 Nagoya, Japan.
authors: Kunio
authors: K
authors: Awaga
authors: ‡Organic Chemistry Institute, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, 48149 Münster, Germany.
authors: Bart Jan
authors: BJ
authors: Ravoo
keywords: active layer; layer-by-layer deposition; organic electronics; photocurrent; photodetector; porphyrin