A simple parallel tandem organic solar cell based on metallophthalocyanines

A simple parallel tandem solar cell based on a combination of Zn-phthalocyanine (Pc) and ClInPc has been fabricated and characterized. Compared to a traditional series tandem cell, parallel tandem cells eliminate the need for a semitransparent recombination layer, reducing the complexity of device fabrication while still providing an excellent increase in device performance. Results show a realized broadening of the spectral response and enhancement of the external quantum efficiency as a result of the complementary absorption profiles of ZnPc and ClInPc in the near infrared region. Introduction of a blended $ClInPc:C60$ layer is shown to more than double the power conversion efficiency of a standard $ZnPc/C60$ bilayer device $(PCE=0.86%)$⁠. The enhanced performance of the parallel tandem $(PCE=1.81%)$ arises from an increase in both the open circuit voltage and the short circuit current.