Improving power efficiencies in polymer—polymer blend photovoltaics

The use of blends of electron and hole transporting polymers has been shown to increase exciton dissociation and efficiency in polymer-based photovoltaics. We compare plain M3EH-PPV devices to M3EH-PPV:CN-ether-PPV blend devices, demonstrating the improved performance of blends. We vary the polymer layer thickness and device electrodes for M3EH-PPV:CN-ether-PPV polymer blend devices to investigate the factors limited device efficiency. We find that although the blends allow exciton dissociation to take place throughout the polymer layer, these devices are still limited by transport properties rather than by light absorption. Our best blend device, made with indium-tin oxide and Ca electrodes, gives a power conversion efficiency ηp=1.0%.