Effect of Hole Transporting Material on Charge Transfer Processes in Zinc Phthalocyanine Sensitized ZnO Nanorods

Abstract

The photoinduced electron transfer processes were studied for hybrid systems consisting of self-assembled monolayer of zinc phthalocyanine (ZnPc) assembled on ZnO nanorods and a film of organic hole transporting material (HTM) atop. Polythiophene (P3HT) or Spiro-OMeTAD were used as HTM. The study was carried out by ultrafast transient absorption spectroscopy technique with selective excitation of ZnPc at 680 nm or P3HT at 500 nm. Data analysis revealed that photoexcitation of ZnPc in the structure ZnO|ZnPc|P3HT results in a fast (1.8 ps) electron transfer from ZnPc to ZnO, which is followed by a hole transfer from the ZnPc cation to P3HT roughly in 30 ps. However, in the case of ZnO| ZnPc|Spiro-OMeTAD structure, the primary reaction upon excitation of ZnPc is a fast (0.5 ps) hole transfer from ZnPc to Spiro-OMeTAD, and the second step is electron injection from the ZnPc anion to ZnO in roughly 120 ps. Thus, we demonstrate two structurally very similar hybrid architectures that implement two different mechanisms for photoinduced charge separation found in dye-sensitized or in organic solar cells.

Photoinduced Electron Injection from Zinc Phthalocyanines into Zinc Oxide Nanorods: Aggregation Effects

“…This is the role of the HTM in dye sensitized solar cells . Second, the primary charge separation reaction may take place at the Pc|spiro-MeOTAD interface, thus changing the sequence of the photoinduced charge transfer reactions. , …”

“…ITO-coated glass substrates (12 × 35 mm, ca. 30 Ω square resistance) were purchased from Solems and cleaned before use as described elsewhere …”

Effect of Co-Adsorbate and Hole Transporting Layer on the Photoinduced Charge Separation at the TiO2–Phthalocyanine Interface

“…at 1000 ps, Figure 8a) and the spectrum of the long-lived component (>20 ns, Figure 8b), respectively, can be attributed to the Spiro cation. 11,34,35,40 It has a band at 530 nm and a broad absorption in the IR region which is observed as a slowly rising absorption toward the longer wavelengths starting from 1000 nm. Therefore, relaxation of the Pc – can be attributed to the electron injection into TiO 2 where τ et is the time constant of the electron transfer from Pc – into TiO 2 .…”

Tetrabenzotriazacorrole and its derivatives as undoped hole transporting materials for perovskite solar cells: Synthesis, device fabrication, and device performance

“…Therefore, there is a strong necessity to develop cost-effective and highly stable HTMs for achieving high-performance and stable PSCs [46] . PTAA (poly(triarylamine) [47] , phthalocyanines (PCs) [40,[48][49][50][51][52][53][54][55][56][57][58][59] , P3HT (poly-3-hexylthiophene) [60] , and graphene oxide [45] have been tested as organic HTMs in PSCs.…”