Technical Proceedings of the 2008 Clean Technology Conference and Trade Show

Clean Technology 2008

Chapter 2: Renewables: Photovoltaics, Wind & Geothermal

J. Valenzuela, S. Mil’shtein
UMass Lowell, US
100 - 104
polymer hetrostructure tandem solar cells
The use of conjugated polymers in solar cell applications has drawn a lot of attention as a way of bringing the high cost of electricity produced by inorganic solar cells to competitive levels. Different research groups fabricated conjugated polymer solar cells which demonstrated efficiency about 5% mainly due to the limited characteristics of the materials. It is well established that sunlight interaction with the polymer solar cells generates excitons with characteristically short diffusion lengths of about 10 nanometers. In the current study we propose the design of a conjugated polymer cell which uses 3 sub-cells arrangement of different available mixtures of donor/fullerene materials. To cover more effectively a bigger range of the solar spectra, 100nm thick bulk heterojunction layers of poly[2-methoxy-5- (3 ,7 -dimethyloctyloxy)-1-4-phenylene vinylene]:phenyl C61-butyric acid methyl ester MDMO-PPV:PCBM (1:4), (poly-3-hexylthiophene): phenyl C61-butyric acid methyl ester P3HT:PCBM (1:1) and poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopen[2,1-b;3,4-b ]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] PCPDTBT:PCBM (1:3) are suggested in our design. The first sub-cell carries an energy gap of 2.47eV, the second one – 1.9eV and the third one – 1.46eV. However the most important is improved absorption of light by these layers, designed to follow the bell shaped spectral dependence of the absorption coefficient.
Design of a Tandem Conjugated Polymer Bulk Heterostructure Solar Cell