Speakers

Prof. Feng Gao is a professor and Wallenberg Academy Fellow at Linköping University in Sweden. He received his Ph.D. from the University of Cambridge in 2011. He received career grants and awards from the European Research Council, the Royal Swedish Academy of Sciences, the Wallenberg Foundation, and Swedish Foundation for Strategic Research. His group currently focuses on research into solution-processed energy materials and devices, mainly based on organic semiconductors and metal halide perovskites.

A New Doping Strategy of Spiro-OMeTAD: Towards Instantly Efficient and Stable Perovskite Solar Cells

Abstract

Record efficiencies of perovskite solar cells (PSCs) are obtained with spiro-OMeTAD as the hole transport layer. Spiro-OMeTAD is conventionally doped by hygroscopic lithium salts with the assistance of volatile 4-tert-butylpyridine, which, however, brings a time-consuming doping process as well as poor device stability. We successfully develop an instantly efficient and clean doping strategy to replace the conventional spiro-OMeTAD doping. As demonstrated by experimental and theoretical investigations, the radical dopant leads to significant increase of the conductivity through efficient hole polarons generation. The ionic salts can further modulate the work function with negligible effects on the film conductivity, critical for reaching optimal open-circuit voltage values by a favorable energetic level alignment. Spiro-OMeTAD based on our new doping strategy enables PSCs with a high power conversion efficiency over 25% and an excellent stability against moisture, heat and illumination. Our findings pave the way for achieving PSCs with high efficiencies and excellent stability at the same time. In addition, our doping strategy goes beyond traditional organic semiconductor doping, providing new understanding of organic doping mechanisms which can inspire further optimizations of different optoelectronic devices.