With seabirds trapped in multipack drink rings, and mid-ocean islands of indestructible rubbish, the idea that plastics could play a big part in a sustainable future world might seem far-fetched. However, new smart photonic and electronic plastics may yet rescue the reputation of this all-consuming 20th century material. Research into such functional plastics for cars and buildings could drastically reduce the need for air conditioning and, thus, improve their energy efficiency. We will present recent efforts to design new plastics of desired photonic and electronic functions targeted for a greener world. One line of our enquiry is to explore the potential of new polymer-based systems that can offer the same flexibility, softness and light weight as commodity plastics but can control the flow of light therefore assisting energy (light) harvesting, e.g., of photovoltaic devices, or light out-coupling from light-emitting diodes. Other opportunities for such systems include photonic heat mirrors that can prevent undesired heat built up of solar cells limiting performance degradation during operation of the cells. Such mirrors also can be exploited to reduce the energy we waste to keep buildings at the temperature we want.