Solvent Engineering for High-Performance PbS Quantum Dots Solar Cells

Rongfang Wu,Miaozi Li,Yuehua Yang,Donghuan Qin,Yangdong Zhang,Lintao Hou

doi:10.3390/nano7080201

Rongfang Wu, Miaozi Li + Show 4 more

Open Access

https://doi.org/10.3390/nano7080201

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Abstract

PbS colloidal quantum dots (CQDs) solar cells have already demonstrated very impressive advances in recent years due to the development of many different techniques to tailor the interface morphology and compactness in PbS CQDs thin film. Here, n-hexane, n-octane, n-heptane, isooctane and toluene or their hybrids are for the first time introduced as solvent for comparison of the dispersion of PbS CQDs. PbS CQDs solar cells with the configuration of PbS/TiO2 heterojunction are then fabricated by using different CQDs solution under ambient conditions. The performances of the PbS CQDs solar cells are found to be tuned by changing solvent and its content in the PbS CQDs solution. The best device could show a power conversion efficiency (PCE) of 7.64% under AM 1.5 G illumination at 100 mW cm−2 in a n-octane/isooctane (95%/5% v/v) hybrid solvent scheme, which shows a ~15% improvement compared to the control devices. These results offer important insight into the solvent engineering of high-performance PbS CQDs solar cells.

Highlights

Colloidal quantum dots (CQDs) heterojunction solar cells that can be fabricated by simple solution-processing techniques are under intensive research due to their potential for low cost, air stable and large area efficient photovoltaic devices [1,2,3,4,5,6,7,8,9,10]
We find that the performance of PbS CQDs solar cells is highly dependent on the content of solvent used
The PbS CQDs are purified by twice precipitating with acetone and ethanol

Summary

Introduction

Colloidal quantum dots (CQDs) heterojunction solar cells that can be fabricated by simple solution-processing techniques are under intensive research due to their potential for low cost, air stable and large area efficient photovoltaic devices [1,2,3,4,5,6,7,8,9,10]. Due to the large surface to volume ratio in CQDs materials, substantial unsaturated dangling bonds will create electronic trap states, which will promote the recombination of charge carriers that is detrimental to the CQDs solar cells performance [13] To overcome this drawback, a series of ligands strategies including organic, organic–inorganic hybrid or atomic ligands have been developed to passivate trap states of CQDs and a dramatic improvement in device performance is obtained [18,19,20,21]. By doping TiO2 with Sb or Zr [22], great improvement of PCEs was obtained in CQD solar cells arising mainly from an increase in short-circuit current (Jsc) Another way to improve the CQD solar cells performance is decreasing the recombination at the metal oxide-semiconductor interface. In this strategy, introducing passivation ligands [23,24,25,26] around CQD can increase the width of the depletion region and optimize the electron collecting efficiency

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