Green fabrication of stable lead-free bismuth based perovskite solar cells using a non-toxic solvent

Sagar M Jain,Tomas Edvinsson,James R Durrant

doi:10.1038/s42004-019-0195-3

Sagar M Jain, Tomas Edvinsson + Show 1 more

Open Access

https://doi.org/10.1038/s42004-019-0195-3

Copy DOI

Abstract

The very fast evolution in certified efficiency of lead-halide organic-inorganic perovskite solar cells to 24.2%, on par and even surpassing the record for polycrystalline silicon solar cells (22.3%), bears the promise of a new era in photovoltaics and revitalisation of thin film solar cell technologies. However, the presence of toxic lead and particularly toxic solvents during the fabrication process makes large-scale manufacturing of perovskite solar cells challenging due to legislation and environment issues. For lead-free alternatives, non-toxic tin, antimony and bismuth based solar cells still rely on up-scalable fabrication processes that employ toxic solvents. Here we employ non-toxic methyl-acetate solution processed (CH3NH3)3Bi2I9 films to fabricate lead-free, bismuth based (CH3NH3)3Bi2I9 perovskites on mesoporous TiO2 architecture using a sustainable route. Optoelectronic characterization, X-ray diffraction and electron microscopy show that the route can provide homogeneous and good quality (CH3NH3)3Bi2I9 films. Fine-tuning the perovskite/hole transport layer interface by the use of conventional 2,2′,7,7′-tetrakis (N,N′-di-p-methoxyphenylamino)−9,9′-spirbiuorene, known as Spiro-OMeTAD, and poly(3-hexylthiophene-2,5-diyl - P3HT as hole transporting materials, yields power conversion efficiencies of 1.12% and 1.62% under 1 sun illumination. Devices prepared using poly(3-hexylthiophene-2,5-diyl hole transport layer shown 300 h of stability under continuous 1 sun illumination, without the use of an ultra violet-filter.

Highlights

The very fast evolution in certified efficiency of lead-halide organic-inorganic perovskite solar cells to 24.2%, on par and even surpassing the record for polycrystalline silicon solar cells (22.3%), bears the promise of a new era in photovoltaics and revitalisation of thin film solar cell technologies
Sources of toxicity for these solar cells can be distinguished into two categories: (1) the inherent toxicity of the water-soluble lead salt present, and (2) the toxic solvents used in the manufacture of devices, such as dimethylformamide (DMF), dimethyl sulfoxide (DMSO), gamma butyrolactone (GBL), chlorobenzene and toluene
The light-absorbing film is made from powder CH3NH3I (MAI) and BiI3 salts in a 1:1.7 molar ratio, dissolved in 1 ml of methyl-acetate following the detailed experimental procedure mentioned earlier

Summary

Introduction

The very fast evolution in certified efficiency of lead-halide organic-inorganic perovskite solar cells to 24.2%, on par and even surpassing the record for polycrystalline silicon solar cells (22.3%), bears the promise of a new era in photovoltaics and revitalisation of thin film solar cell technologies. The large possibilities in elemental composition and local arrangements of cations allow fine-tuning of the optoelectronic properties of the perovskite absorber, where the high-yield performance and band gap tuning make them promising in both single-junction devices and multi-junction tandem applications Solution processing of these solar cells potentially allows low cost, large-scale manufacturing, possibly providing an alternative to crystalline silicon, CdTe or CIGS solar cells, or as a potentially cheap tandem material to be used in a hybrid tandem solar cell together with conventional PV technology. Sources of toxicity for these solar cells can be distinguished into two categories: (1) the inherent toxicity of the water-soluble lead salt present, and (2) the toxic solvents used in the manufacture of devices, such as dimethylformamide (DMF), dimethyl sulfoxide (DMSO), gamma butyrolactone (GBL), chlorobenzene and toluene These solvents have low exposure limits, and are not compatible with low cost, large-scale printing techniques in an ambient environment.

Methods

Results

Conclusion