All-organic tunnel junctions as connecting units in tandem organic solar cell

We employed organic heterojunction films as all-organic connecting units to fabricate tandem organic photovoltaic cells by continuous deposition. The all-organic connecting units with a better transparence and a lower sublimation temperature became an effective recombination center for electrons and holes photogenerated in front cell and back cell, respectively. Tunnel mechanism was proposed to explain the combination of photogenerated carrier. In the optimized tandem solar cell in which tin phthalocyanine dichloride/copper hexadecafluorophthalocyanine heterojunction is used as connecting units, the open-circuit voltage of 1.04 V is double of the single unit cells, and the PCE was increased by 60%, reaching to 1.8%. Therefore, it is an effective way to use the organic heterojunction films as connecting units in organic tandem cells to improve the device performance dramatically. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3033485]