Controlled self-assembly of porphyrin/fullerene donor-acceptor complex in a polymer thin film

Abstract

Thin films composed of polycyclohexane (PCHE), zinc(II)-5,10,15,20-tetra-(2-naphthyl)porphyrin (ZnTNpP), and [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) blends are prepared to investigate their potential for the controlled selfassembly of a porphyrin/fullerene donor-acceptor complex in a polymer thin film. The compatibilities of PCHE/PCBM (p), PCHE/ZnTNpP (q), and ZnTNpP/PCBM (r) in these blends have a significant effect on the dispersion of the ZnTNpP/PCBM donor-acceptor complex in the PCHE thin film. When the compatibilities are p << q, r, and q r, the ZnTNpP/PCBM donor-acceptor complex is formed between the PCHE and PCBM phases. This concept to form a controlled self-assembly of the ZnTNpP/PCBM donor-acceptor complex may be applied to various combinations of porphyrin/fullerene systems in polymer thin film solar cells to achieve excellent performance.

Controlled dispersion of a porphyrin/fullerene donor‐acceptor complex in semiconducting polymer thin films: Intermolecular interactions of polymers with porphyrin and fullerene

“…As reported in a previous article, the optical properties of ZnTNpP were strongly influenced by the state of the molecules. In the UV–vis spectra, the Soret band of ZnTNpP was shifted to longer wavelengths with increasing degrees of aggregation, and so the degree of aggregation of ZnTNpP in the polymer thin film was examined by the assessment of the extent of the redshift of the Soret band (Scheme ).…”

“…In the UV–vis spectra, the Soret band of ZnTNpP was shifted to longer wavelengths with increasing degrees of aggregation, and so the degree of aggregation of ZnTNpP in the polymer thin film was examined by the assessment of the extent of the redshift of the Soret band (Scheme ). As shown in Figure , in the case of free ZnTNpP molecules (e.g., in a 0.00150 mg/mL THF solution), the Soret band was observed at 429 nm (line X). In contrast, when all of the ZnTNpP molecules were in direct contact, as in the spin‐coated thin film, the Soret band was observed at 446 nm (line Y).…”

“…Accordingly, the ZnTNpP molecules seemed to have been well dispersed throughout the PVNP phase, even though excess PCBM molecules were added in the blend, as in the 60/10/30 PVNP/ZnTNpP/PCBM blend [Figure (d)]. In such cases, when the strength of the intermolecular interactions between the ZnTNpP and the PCBM was sufficiently strong compared to that between the PVNP/PCBM and PVNP/ZnTNpP, one would expect that all of the ZnTNpP molecules would be dispersed in the PVNP phase in the form of ZnTNpP/PCBM donor–accepter complexes . To examine the strengths of the intermolecular interactions of the porphyrin/fullerene system in the PVNP/ZnTNpP/PCBM blend, the PL spectra of the polymer thin films were acquired.…”

“…Recently, we proposed the tuning of the molecular compatibilities (i.e., intermolecular interactions) of polymer/fullerene, polymer/porphyrin, and porphyrin/fullerene (Scheme ) systems as a new concept for the controlled dispersion of porphyrin molecules into polymer thin films . For example, when polycyclohexane (PCHE; a hydrocarbon polymer), zinc(II)−5,10,15,20‐ tetra ‐(2‐naphthyl)porphyrin (ZnTNpP; a porphyrin derivative), and [6,6]‐phenyl‐C 61 ‐butyric acid methyl ester (PCBM; a fullerene derivative) were blended, a clear microphase separation of PCHE and PCBM was observed, and a ZnTNpP/PCBM donor–acceptor complex layer was formed between the PCHE and PCBM phases . Furthermore, we have demonstrated the ready formation of porphyrin/fullerene donor–acceptor complexes in various polymer thin films, in which the intermolecular interactions caused by charge‐transfer from porphyrin to fullerene within the porphyrin/fullerene complex appear to be very strong .…”

“…For example, when polycyclohexane (PCHE; a hydrocarbon polymer), zinc(II)−5,10,15,20‐ tetra ‐(2‐naphthyl)porphyrin (ZnTNpP; a porphyrin derivative), and [6,6]‐phenyl‐C 61 ‐butyric acid methyl ester (PCBM; a fullerene derivative) were blended, a clear microphase separation of PCHE and PCBM was observed, and a ZnTNpP/PCBM donor–acceptor complex layer was formed between the PCHE and PCBM phases . Furthermore, we have demonstrated the ready formation of porphyrin/fullerene donor–acceptor complexes in various polymer thin films, in which the intermolecular interactions caused by charge‐transfer from porphyrin to fullerene within the porphyrin/fullerene complex appear to be very strong . In addition, we noticed that the tracking location of maxima of the Soret band of porphyrin acted as a good indicator to reveal the degree of its aggregation in polymer/porphyrin blends.…”