Solar cells based on organic molecules and polymers

The search of clean, inexpensive and renewable energy sources is one of the most important challenges that the mankind is currently confronting. Recently there has been a notable interest of the scientific community to develop organic photovoltaic (OPV) technology as a mean of renewable energy source since it combines low-cost and easy fabrication. We have fabricated and tested plastic solar devices (OPVs) by using the bulk heterojunction approach. OPVs were prepared by blending 6-Nitro-3-(E)-3-(4-dimethylaminophenyl)allylidene)-2,3 dihydrobenzo[d][1,3,2]-oxazaborole (M1) and (E)-3-(4-Dimethylaminophenyl)allylidene)-2,3-dihydrobenzo[d]-[1,3,2]oxazaborole (M2), which are conjugated and non-linear low molecular weight molecules prepared in our laboratories, and the well known photoconductor polymer MEH-PPV; fullerene PC61BM was the sensitizer. The morphology of thin polymer films prepared by using the spin coating technique was analyzed by Atomic Force Microscopy (AFM). For the electric contact, commercial and transparent indium tin oxide (ITO) deposited on glass slides was used, and a metal alloy of Pb/Bi/Cd/Sn as cathode, was easily deposited on the polymer film by melting the alloy at 75 °C. Open circuit voltages (Voc) of ~ 700 mV and short circuit currents (Jsc) of ~ 0.75 mA/cm2 under solar (AM1.5) illumination were measured for MEH-PPV and M1 based samples. For OPVs cells based on mixtures of either M1 and MEH-PPV or M2 and MEH-PPV there was a large electrical enhancement showing Voc ~ 700 mV and Jsc ~ 2.0 mA/cm2. OPVs cells were also tested under Xe-lamp illumination. Measurements from the I-V curves gave electrical efficiencies close to 1%.