Study of P3HT:PCBM bulk heterojunction solar cells: influence of components ratio and of the nature of electrodes on performances and lifetime

Among the class of conjugated polymers, polythiophenes and in particular 3-alkyl-substituted thiophenes seem to focus all the attention in the domain of photovoltaic conversion. At CEA, we are working on the optimization of bulk heterojunction solar cells made of poly-3-hexylthiophene (P3HT)and [6,6]-phenyl C 61 butyric acid methylester (PCBM) blend. First we will describe the influence of the ratio of P3HT and PCBM blend on the efficiency of the resulting bulk heterojunction solar cells. Best cells based on 1:1 in weight ratio yield 3.6 % power conversion efficiency under air-mass 1.5, 100 mW/cm 2 illumination. Then we will compare the efficiency and lifetime of different cells by changing the nature and thickness of cathode (Aluminum or Calcium/Silver). On the optimized cells, we have proceeded to ageing and accelerated lifetime measurements on devices with Ca/Ag cathode. It shows that the current densities decrease less than 3 % and that efficiency is still higher than 1.7 %, after 400 hours under AM 1.5, 100 mW/cm 2 illuminations and at high temperature (60°C).