Assessing the Potential Roles of Silicon and Germanium Phthalocyanines in Planar Heterojunction Organic Photovoltaic Devices and How Pentafluoro Phenoxylation Can Enhance π–π Interactions and Device Performance

Abstract

In this study, we have assessed the potential application of dichloro silicon phthalocyanine (Cl2-SiPc) and dichloro germanium phthalocyanine (Cl2-GePc) in modern planar heterojunction organic photovoltaic (PHJ OPV) devices. We have determined that Cl2-SiPc can act as an electron donating material when paired with C60 and that Cl2-SiPc or Cl2-GePc can also act as an electron acceptor material when paired with pentacene. These two materials enabled the harvesting of triplet energy resulting from the singlet fission process in pentacene. However, contributions to the generation of photocurrent were observed for Cl2-SiPc with no evidence of photocurrent contribution from Cl2-GePc. The result of our initial assessment established the potential for the application of SiPc and GePc in PHJ OPV devices. Thereafter, bis(pentafluoro phenoxy) silicon phthalocyanine (F10-SiPc) and bis(pentafluoro phenoxy) germanium phthalocyanine (F10-GePc) were synthesized and characterized. During thermal processing, it was discovered that F10-SiPc and F10-GePc underwent a reaction forming small amounts of difluoro SiPc (F2-SiPc) and difluoro GePc (F2-GePc). This undesirable reaction could be circumvented for F10-SiPc but not for F10-GePc. Using single crystal X-ray diffraction, it was determined that F10-SiPc has significantly enhanced π-π interactions compared with that of Cl2-SiPc, which had little to none. Unoptimized PHJ OPV devices based on F10-SiPc were fabricated and directly compared to those constructed from Cl2-SiPc, and in all cases, PHJ OPV devices based on F10-SiPc had significantly improved device characteristics compared to Cl2-SiPc.

Boron Subphthalocyanines and Silicon Phthalocyanines for Use as Active Materials in Organic Photovoltaics

“…has introduced the use of phenoxy‐substituted silicon phthalocyanines, which may be synthesized in a straightforward reaction combining Cl 2 ‐SiPc with an excess of a phenol in refluxing chlorobenzene overnight (Scheme iv). This reaction gives the bis(phenoxy) silicon phthalocyanine in yields above 80 % . More recent studies have explored carboxylate‐substituted silicon phthalocyanines, which may be similarly synthesized by mixing Cl 2 ‐SiPc with an excess of a carboxylic acid in refluxing diglyme or toluene, depending on the solubility of the reagent (Scheme v,vi).…”

“…In a preliminary study, Lessard et al . explored the use of dichlorosilicon phthalocyanine (Cl 2 ‐SiPc) and bis(pentafluoro phenoxy)silicon phthalocyanine (F 10 ‐SiPc) as both donors and acceptors in PHJ devices . It was found that despite nearly identical optoelectrical properties, the F 10 ‐SiPc outperformed Cl 2 ‐SiPc both as a donor and as an acceptor, achieving efficiencies up to 0.40 % as an acceptor paired with α‐6T and up to 0.45 % as a donor paired with pentacene.…”

Silicon Phthalocyanines as Acceptor Candidates in Mixed Solution/Evaporation Processed Planar Heterojunction Organic Photovoltaic Devices

“…Recently, SiPcs have attracted significant interest from our group and others for their integration into OPVs, both as an additive in BHJ devices [48][49][50][51] or as an acceptor or donor in either BHJ or PHJ devices [52][53][54]. We reported the use of bis(6-azidohexanoate)silicon phthalocyanine ((HxN 3 ) 2 -SiPc) as the first dual function ternary additive for OPV, which improved the device stability through cross linking while simultaneously increasing the PCE by absorbing in the near IR region [49].…”

Electrical and photovoltaic characteristics of indium phthalocyanine chloride/p-Si solar cell

“…These results further exemplify that the seemingly minor change from chloride to fluoride in the AlPc structure has significant implications in optoelectronic properties and functionality of AlPc in PHJ OPV devices. Lessard et al [14] have assessed the potential application of dichloro silicon phthalocyanine (Cl 2 -SiPc) and dichloro germanium phthalocyanine (Cl 2 -GePc) in modern planar heterojunction organic photovoltaic (PHJ OPV) devices. The results established the potential for the application of SiPc and GePc in PHJ OPV devices.…”