Recent developments in solution processable single junction polymer solar cells have led to a significant improvement in power conversion efficiencies from ∼5% to beyond 9%. While much of the initial efficiency improvements were driven through judicious design of donor polymers, it is the engineering of device architectures through the incorporation of inorganic nanostructures and better processing that has continued the efficiency gains. Inorganic nano-components such as carbon nanotubes, graphene and its derivatives, metal nanoparticles and metal oxides have played a central role in improving device performance and longevity beyond those achieved by conventional 3G polymer solar cells. The present work aims to summarise the diverse roles played by the nanosystems and features in state of the art next generation (4G) polymer solar cells. The challenges associated with the engineering of such devices for future deployment are also discussed.

Transparent, highly percolated networks of regio-regular poly(3-hexylthiophene) (rr-P3HT) wrapped semiconducting single walled carbon nanotubes (s-SWNT) are deposited and the charge transfer processes of these nanohybrids are studied using spectroscopic and electrical measurements. The data discloses hole doping of s-SWNTs by the polymer, challenging the prevalent electron doping hypothesis. Through controlled fabrication, high to low-density

Photoluminescence quenching is observed in acid functionalized multiwall carbon nanotubes incorporated polymer: fullerene films, suggesting efficient charge transfer, believed to be due to nanotubes acting as exciton dissociation centres. The fabricated photovoltaic devices with triple heterojunction interfaces show increased short circuit current density compared to the device without nanotubes.

Multiwall carbon nanotubes are introduced into poly͑3-hexylthiophene͒ and ͓6,6͔ phenyl C 61 butyric acid methyl fullerene, bulk heterojunction organic photovoltaic devices. Utilization of nanotubes requires chemical modifications for compatibility with solution processable photovoltaics. Better dispersions of carbon nanotubes in organic solvents are achieved by acid functionalization of tubes. Pristine and acid treated multiwall carbon nanotubes have been incorporated into the photoactive layer and better results in fill factors of 62% and efficiency of 2.3% are achieved under Air Mass 1.5 Global illumination through the use of acid treated nanotubes.

We have successfully prepared mono-and bi-