This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2019 New J. Chem. Cite this: DOI: 10.1039/c8nj06389c 3D hybrid perovskite solid solutions: a facile approach for deposition of nanoparticles and thin films via B-site substitution† Muhammad Aamir, a Rana Farhat Mehmood, b Arshad Farooq Butt, a Malik Dilshad Khan, c Mohammad Azad Malik, d Neerish Revaprasadu, c Jean-Michel Nunzi, e Muhammad Sher f and Javeed Akhtar * a Mixed metal halide perovskites are gaining paramount interest due to efficient band gap tenability and improved optical properties compared to their single metal halide perovskites. It is thus valuable to investigate compositional changes in lead halide perovskites to explore energy changes. Herein, we report the synthesis of a lead to lead free hybrid perovskite solid solution (CH 3 NH 3 Pb 1Àx Cu x Br 3 ) as nanoparticles and films. The increasing concentration of Cu 2+ ions in the site of the Pb 2+ ion in the perovskite shifted the diffraction peaks to a larger angle. Uniform spherically shaped nanoparticles were synthesized by a wet chemical method, the higher Cu 2+ concentration leads to agglomeration, producing sheet like morphologies. However, the deposition of thin films of CH 3 NH 3 Pb 1Àx Cu x Br 3 perovskite solid solution shows that well defined morphologies begin to appear with increasing concentrations of Cu 2+ in the perovskite structure. The as-prepared bulk lead free CH 3 NH 3 CuBr 3 perovskite shows a band gap of 1.65 eV. A blue shift in photoluminescence (PL) was observed with copper enriched hybrid perovskites. Introduction The recent, robust development of perovskite materials has revolutionized the photovoltaics research field with the highest certified solar light conversion efficiency reported to be over 20%. 1–4 Metal halide perovskites exhibit ideal properties for applications including photovoltaics, 5,6 sensing, 7–9 photo- catalysis, 10 piezoelectrics 11,12 and lasing 13 due to a tunable band gap, 14,15 low exciton binding energy, 16,17 long carrier diffusion lengths 18,19 and broad band emission. 20,21 Despite the record efficiency, one major concern with this material is the toxicity of lead. Therefore, a key challenge is to replace lead with less toxic metals, however, no compatible success has been reported so far. Although, Pb has been replaced with its group members, Sn and Ge, the stability of the 2+ oxidation state decreases while moving up this group, which limits the use of these metals in the synthesis of stable metal halide perovskites. In particular, Sn has been widely studied as an alternative to Pb, but, it undergoes oxidation from Sn 2+ to Sn 4+ in which Sn 4+ act as a p-type dopant by a self-doping process. 22–24 The partial incor- poration of Sn in the CH 3 NH 3 PbI 3 perovskite tunes the optical properties. 23 Recently, Zhang et al. 25 have reported the gradual substitution of Sb 3+ in the Pb 2+ site of CH 3 NH 3 PbI 3 perovskites to tailor the optoelectronic properties, and tuned the band gap from 1.55 eV to 2.06 eV. However, the complete interconversion of CH 3 NH 3 PbI 3 to the layered CH 3 NH 3 Sb 0.66 I 3 perovskite leads to reduced photovoltaic efficiency. Only 1% Sb doping in CH 3 NH 3 PbI 3 was found to improve the V oc , FF and I sc of the solar cell. 25 These shortcomings drew the attention of the scientific community to exploring other substitutes for Pb. Transition metals, particularly attractive metals, such as, Fe 2+ , Cu 2+ etc. can be used to investigate potential alternatives to lead-based perovskites. Taking this into consideration there is an urge to develop alternative transition metal based perovskites due to their chemical stability, reduced toxicity and abundance. Herein, we have attempted for the first time, the synthesis, characterization and fabrication of nanoparticles and bulk perovskite solid solutions obtained by the incorporation of a Materials laboratory, Department of Chemistry, Mirpur University of Science & Technology (MUST), Mirpur-10250 (AJK), Pakistan. E-mail: javeed.chem@must.edu.pk b Department of Chemistry, University of Education Lahore, Dera Ghazi Khan Campus, Kangan Road, DG khan, Pakistan c Department of Chemistry, University of Zululand, Private Bag X1001, Kwadlangezwa, 3886, South Africa d School of Materials, The University of Manchester, Oxford Road, M13 9PL, UK e Department of Chemistry, Queen’s University, Kingston, ON K7L 3N6, Canada f Department of Chemistry, Allama Iqbal Open University, Islamabad, Pakistan † Electronic supplementary information (ESI) available. See DOI: 10.1039/c8nj06389c Received 25th December 2018, Accepted 11th March 2019 DOI: 10.1039/c8nj06389c rsc.li/njc NJC PAPER Published on 12 March 2019. Downloaded by University of Rochester on 3/20/2019 6:08:29 AM. View Article Online View Journal