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

• Published in: Communications chemistry 2019-08, Vol.2 (1), Article 91
• Main Authors: Jain, Sagar M., Edvinsson, Tomas, Durrant, James R.
• Format: Article
• Language: English
• Subjects: 639/301/299/946; 639/4077/909/4101; 639/925/357/551; Antimony; Bismuth; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Energy conversion efficiency; Environmental legislation; Illumination; Lead compounds; Lead free; Metal halides; Optoelectronics; Perovskites; Photovoltaic cells; Reagents; Regeneration; Solar cells; Solvents; Sun; Thin films; Titanium dioxide; Transport
• ISSN: 2399-3669; 2399-3669
• DOI: 10.1038/s42004-019-0195-3

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 (CH 3 NH 3 ) 3 Bi 2 I 9 films to fabricate lead-free, bismuth based (CH 3 NH 3 ) 3 Bi 2 I 9 perovskites on mesoporous TiO 2 architecture using a sustainable route. Optoelectronic characterization, X-ray diffraction and electron microscopy show that the route can provide homogeneous and good quality (CH 3 NH 3 ) 3 Bi 2 I 9 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. Perovskites are widely studied as components of solar cells but their synthesis often involves toxic reagents. Here lead-free bismuth-based perovskites are synthesised using a non-toxic solvent and shown to achieve power conversion efficiencies of up to 1.62 % under 1 sun illumination for up to 300 h.