N‑Type Solution-Processed Tin versus Silicon Phthalocyanines: A Comparison of Performance in Organic Thin-Film Transistors and in Organic Photovoltaics

Tin­(IV) phthalocyanines (SnPcs) are promising candidates for low-cost organic electronic devices, and have been employed in organic photovoltaics (OPVs) and organic thin-film transistors (OTFTs). However, they remain relatively understudied compared to their silicon phthalocyanine (SiPc) analogues. Previously, we reported the first solution-processed SnPc semiconductors for OTFTs and OPVs; however, the performances of these derivatives were unexpected. Herein to further study the behavior of these derivatives in OPVs and OTFTs, we report the synthesis along with optical and thermal characterization of seven axially substituted (OR)₂-SnPcs, five of which were synthesized for the first time. Density functional theory (DFT) was used to predict charge-carrier mobilities for our materials in their crystal state. The application of these SnPcs as ternary additives in poly­(3-hexylthiophene) (P3HT)/phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) OPVs and as semiconductors in solution-processed n-type OTFTs was also investigated. When employed as ternary additives in OPVs, all (OR)₂-SnPcs decreased the power conversion efficiency, open-circuit voltage, short-circuit current, and fill factor. However, in OTFTs, four of the seven materials exhibited greater electron field-effect mobility with similar threshold voltages compared to their previously studied SiPc analogues. Among these SnPcs, bis­(triisobutylsilyl oxide) SnPc displayed the greatest electron field-effect mobility of 0.014 cm² V^–1 s^–1, with a threshold voltage of 31.4 V when incorporated into OTFTs. This difference in electrical performance between OTFT and OPV devices was attributed to the low photostability of SnPcs.