Zhicai He
South China University of Technology, China
Title: Loss mechanism in the open circuit voltage of polymer solar cells
Biography
Biography: Zhicai He
Abstract
Polymer solar cells(PSCs) have become a promising candidate for next-generation photovoltaics because the advantages of flexible, lightweight, large-area devices and room-temperature solution processible.Dispite the power conversion efficiencies(PCE) of single junction PSCs has been improve to 10% recently,the open circuit voltage(VOC) is still qiute far away from the theoretic limit.Therefore it will open a new opportunities to further improve the PCE if the gap between the open circuit voltage and the bandgaps of the donor materials can be minmized.So the study on the formation and the loss mechanism of VOC is in urgent need.In our recent work , the fundamental losses in VOC of PSCs based on narrow bandgap polymers was found to can be effectively alleviated and be modulated over a wide range through the control over the band tailing below the LUMO of PC71BM. By combining the analysis on the electrical, photocurrent spectral response characteristics of the working devices and the results from structure characterizations, the band tailing and the concomitant increase in the splitting of the electron and hole quasi-Fermi levels were found to be responsible for the VOC. And a correlation between the band tailing and the photovoltage output of the device was established ,thus can provide more insight into the origins and loss mechanism of the VOC and guidelines for further improvement through either materials chemistry or device optimization.
