The invention relates to substituted ullazine and analogs of ullazine as sensitizers for dye-sensitized solar cells (DSSCs) and other photoelectrochemical and/or optoelectronic devices. The sensitizers may comprise donor substituents and/oracceptor substituents, besides an anchoring group suitable for attaching the sensitizer on a semiconductor surface. DSSCs based on this type of sensitizers exhibit high power conversion efficiencies.