Photovoltaics from soluble small molecules

Solution-processable small molecules have attractive features for application in photovoltaic cells. They offer the facile processing associated with polymers, yet are easier to synthesize and purify, are monodisperse, and typically show higher charge carrier mobilities. Recent progress in solution-processable small molecule blends has yielded photovoltaic cells with efficiencies exceeding 1%. This article reviews progress in this nascent field and discusses the requirements imposed by the need for charge separation within an interpenetrating network, energy level tuning for light absorption and voltage output, and processing techniques to achieve phase separation on excitonic length scales. Design criteria for next-generation materials are provided.