Light-Induced Interfacial Dynamics Dramatically Improve the Photocurrent in Dye-Sensitized Solar Cells: An Electrolyte Effect.

Jiajia Gao,Luca D’Amario,Valentina Leandri,Erik Gabrielsson,Gunther Andersson,Ahmed M El-Zohry,Hanna Ellis,Majid Safdari,Herri Trilaksana,Lars Kloo,James M Gardner

doi:10.1021/acsami.8b06897

Abstract

A significant increase in the photocurrent generation during light soaking for solar cells sensitized by the triphenylamine-based D-π-A organic dyes (PD2 and LEG1) and mediated by cobalt bipyridine redox complexes has been observed and investigated. The crucial role of the electrolyte has been identified in the performance improvement. Control experiments based on a pre-treatment strategy reveals TBP as the origin. The increase in the current and IPCE has been interpreted by the interfacial charge-transfer kinetics studies. A slow component in the injection kinetics was exposed for this system. This change explains the increase in the electron lifetime and collection efficiency. Photoelectron spectroscopic measurements show energy shifts at the dye/TiO2 interface, leading us to formulate a hypothesis with respect to an electrolyte-induced dye reorganization at the surface.

Highlights

The record efficiency is not impressive compared with other photovoltaic technologies, in particular with respect to perovskite-type hybrid solar cells, dye-sensitized solar cells (DSSCs) still represent a perfect model for the fundamental study of charge-transfer dynamics, which can provide insights into structural and material engineering
The first and foremost step of charge transfer occurs at the dye/semiconductor interface in the kinetics ranging from femtosecond to millisecond
When exposing LEG1- and PD2-sensitized solar cells containing the optimized cobalt bipyridine electrolyte under open-circuit conditions to the light soaking for extended periods of time, the device efficiency significantly increase; see Figure 2, which containing a D35-type donor (Figure S1) and a bithiophene group as π-linker but with two different anchoring groups

Summary

Introduction

Over the past two decades, the power conversion efficiency of dye-sensitized solar cells (DSSCs) has increased to over 13%.1 the record efficiency is not impressive compared with other photovoltaic technologies, in particular with respect to perovskite-type hybrid solar cells, DSSCs still represent a perfect model for the fundamental study of charge-transfer dynamics, which can provide insights into structural and material engineering. According to a pre strategy, the dye-sensitized TiO2 film or electrode was pretreated under light exposure in a dummy cell with the dummy electrolyte containing certain component(s) as noted and isolated.

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Conclusion