This review highlights the most relevant works on phthalocyanines, porphyrins and other porphyrinoids as components of perovskite solar cells from the last four years acting as hole transporting materials, additives, and interlayers.

Diketopyrrolopyrroles stand out due to their chemical and optoelectronic properties. Diketopyrrolopyrrole-single molecules applied in organic, dye-sensitized and perovskite solar cells are presented to give clues for future molecular optimizations.

Enriched semiconducting single-walled carbon nanotubes (SWCNT (6,5) and SWCNT (7,6)) and HiPco nanotubes were covalently functionalized with either zinc phthalocyanine or silicon phthalocyanine as electron donors. The synthetic strategy resulted in edge-on and face-on geometries with respect to the phthalocyanine geometry, with both phthalocyanines held by an electronically conducting diphenylacetylene linker. The extent of functionalization in the MPc-SWCNT (M = Zn or Si) donor–acceptor nanohybrids was determined by systematic studies involving AFM, TGA, XPS, optical and Raman techniques. Intramolecular interactions in MPc-SWCNT nanohybrids were probed by studies involving optical absorbance, Raman, luminescence and electrochemical studies. Different degrees of interactions were observed depending on the type of MPc and mode of attachment. Substantial quenching of MPc fluorescence in these hybrids was observed from steady-state and three-dimensional fluorescence mapping, which suggests the occurrence of excited state events. Evidence for the occurrence of excited state charge transfer type interactions was subsequently secured from femtosecond transient absorption studies covering both the visible and near-infrared regions. Furthermore, electron-pooling experiments performed in the presence of a sacrificial electron donor and a second electron acceptor revealed accumulation of one-electron reduced product upon continuous irradiation of the nanohybrids. In such experiments, the ZnPc-SWCNT (6,5) nanohybrid outperformed other nanohybrids and this suggests that this is a superior donor–acceptor system for photocatalytic applications.

We developed triple bonded π-conjugated zinc-phthalocyanine dimers (ZnPc-t-DPP-t-ZnPc 1, ZnPc-t-t-ZnPc 2, ZnPc-t-Spiro-t-ZnPc 3) through molecular engineering, and these dimers were then employed as hole selective layers for the fabrication of perovskite solar cells (PSCs). The designed dimers showed band alignment with a mixed cation perovskite, and efficient charge extraction capability, thus allowing subsequent improvement in the performance of the PSCs. The fabricated PSC with the dimer ZnPc-t-Spiro-t-ZnPc 3 surpasses the PSC performance based on the state-of-the-art Sprio-OMeTAD. ZnPc dimers displayed improved long-term stability under stress conditions.