Electro‐Optical Study of Subphthalocyanine in a Bilayer Organic Solar Cell

Abstract

Ultra‐thin films of subphthalocyanine (SubPc) were grown onto Si/SiO2 substrates by organic molecular beam deposition and the complex refractive index has been characterized by spectroscopic ellipsometry. The peak maximum in the extinction coefficient is determined to be 1.6 at 590 nm and the dielectric constant equals 3.9 in the limit of long wavelength. These values are extraordinary high when compared to the well‐known metal‐phthalocyanines and will be beneficial for the performance in a photovoltaic cell. The amorphous SubPc structure on top of indium‐tin‐oxide (ITO) as well as quartz glass is imaged by atomic force microscopy and scanning electron microscopy and we have characterized the nearly flat surface topology. Next, subphthalocyanine films in combination with buckminsterfullerene (C60) have been studied in a planar bilayer donor/acceptor heterojunction by current density‐voltage characterization under AM 1.5 simulated illumination at various light intensities. A power conversion efficiency of 3.0 % under 1 sun was measured. Finally, the external and internal quantum efficiencies demonstrated peak maxima at 590 nm of 46 % and 55 %, respectively. Considering the abrupt junction at the donor/acceptor interface, the electron transfer from SubPc to the acceptor material is thus determined to be highly efficient.

Graded Donor‐Acceptor Heterojunctions for Efficient Organic Photovoltaic Cells

“…Overall, η P = (4.2 ± 0.1)% is obtained for the NZEP (1:4) GHJ at 100 mWcm − 2 , compared to η P = (3.7 ± 0.1)% for an optimized mixture, and η P = (3.0 ± 0.1)% for a planar architecture (Figure 4c ). The operating parameters obtained for the planar OPV cell are consistent with those published elsewhere for the same device architecture, [ 22 ] while OPVs based on mixtures and gradients of SubPc and C 60 have not been previously examined. Based on this work, it is concluded that GHJs are an attractive approach to enhance the effi ciency of small molecule OPVs.…”

Electronic Structure of C60/Phthalocyanine/ITO Interfaces Studied using Soft X-ray Spectroscopies

“…28 Gommans et al has also reported molecular disorder for SubPc on ITO on the basis of microscopy studies. 29 Since SubPc molecules on ITO are disordered, a much lower SubPc layer thickness must be used to enhance I SC and for optimal device performance.…”

Layer‐by‐Layer Processed Organic Solar Cells

“…Fused acenes [34][35][36][37][38][39][40][41][42][43] and several famous classes of dyes, such as phthalocyanine (Pc), [20, subphthalocyanine (SubPc), [66][67][68][69][70][71] subnaphthalocyanine (SubNc), [72,73] merocyanine (MC), [74] cyanine dyes, [75][76][77][78][79] and squaraine (SQ), [80][81][82][83] are widely used in LL vacuum deposited OPVs (Figure 2, Table 1). In 2001, Forrest and Peumans fabricated bilayer heterojunction OPVs based on CuPc and C 60 with a PCE of 3.6% under 150 mW cm −2 simulated AM1.5G illumination.…”