Study on charge separation and collection for stable mesoscopic sensitized solar cells

Abstract

Dye-sensitized solar cells (DSCs) is a possible economic alternative to conventional silicon-based photovoltaics and have achieved 12.3% power conversion efficiency (PCE). However, lacking of long-term stability has always been an issue and cancels out the advantage of high watt/price ratio. In this work, the correlation of key photovoltaic parameters with important thermodynamic and kinetic factors of DSCs upon aging was firstly carefully examined, giving a general idea about the system. After that, with a newly designed transistor-like device, the charge collection in solid-state DSCs, which may be suitable for long-term application as no liquid electrolyte is used, was investigated by impedance spectroscopy (IS), which reveals the inefficient electron collection in ss-DSCs rather than hole collection. Then the dye regeneration and electron dye recombination processes in different kinds of stable liquid DSCs were thoroughly investigated with transient absorption technique and IPCE(incident photon to current efficiency)/IS, validating the model based on continuity equation and showing the limitation of inefficient regeneration on PCE. These works provide novel and insightful information to the charge separation and collection processes in stable DSCs, whose PCEs are relatively low and can be enhanced with the these processes optimized.