Evaluation of characteristics on the bulk heterojunction solar cells prepared by PCDTBT: PC71BM composite thin film

Bulk heterojunction (BHJ) solar cells based on blends comprising conjugated polymers and fullerene acceptors are the subject of considerable investigation because of their potential to enable the fabrication of low-cost devices that convert sunlight into electricity. Recently, poly(2,7-carbazole) derivatives have gained momentum as a class of promising alternative materials to poly(3-hexylthiophene) (P3HT) in organic solar cell applications. Among them, poly[N-900-hepta-decanyl-2,7-carbazole-alt-5,5-(40,70-di-2-thienyl-20,10,30-benzo thiadiazole)] (PCDTBT) has a relatively deeper highest occupied molecular orbital (HOMO) of 5.45 eV compared to the HOMO of 5.1 eV of the P3HT. In this work we systematically study the effect of donor and acceptor ratio on the device performance of bulk heterojunction solar cells made with blends of PCDTBT and PC 71 BM. We used PEDOT: PSS as a hole transport layer, and TiOX as a hole-blocking layer in order to improve the power conversion efficiency. The current density-voltage (JV) characteristics of photovoltaic cells were measured under the illumination of simulated solar light with 100 mW/cm 2 (AM 1.5G) by an Oriel 1000 W solar simulator. The power conversion efficiency of the solar cell is more than 5%.