Lead free organometal halide perovskites for photovoltaic applications

Abstract

Perovskites have risen up the research community in optoelectronic with its propitious applications. More notably in Photovoltaics perovskite has established a platform for researchers over traditional silicon solar cells. Within the last few years, halide perovskites become a very promising photovoltaic material, fascinating the research community. The most efficient devices exceed 22% solar to electrical power conversion efficiency. Where the perovskite emerges as an excellent light absorber. Mostly lead based perovskites have significant efficiency, but leading an environment friendly and more stable photovoltaic research the issues of toxicity of lead and less stability have been considered. A profusion research have been done to replace lead to get nontoxicity and stability, here we have focused on preparing lead free bismuth based organometallic halide perovskite for photovoltaic applications, as it is found that bismuth is more appropriate element for replacement due to its less-toxicity and stability in solar cells. (CH3NH3)3Bi2I9 has been studied by different research community with many possible ways that may enhance its efficiency. Here in this project attempts have been made to prepare methyl-ammonium bismuth iodide (MBI) with combinations of different solvents and different concentrations. To determine the structural, optical and morphological properties of MBI X-ray diffraction (XRD), UV-Visible, and Field Emission Scanning Electron Microscope (FE-SEM) characterizations, respectively, are performed and a comparative analysis have been done. X-ray diffraction pattern studies confirms the formation of phase pure TiO2, perovskite materials. Formation of hexagonal structure oriented along the c-axis evidenced the formation of MBI perovskites. The optical characterization confirms the strong visible absorption of MBI with an optical bandgap of 1.69-2.05 eV. To check the stability of MBI XRD and FESEM analysis has been done after intervals of 10 days. Degradation can be seen after 25-30 days in MBI perovskite.However MBI was identified as a good candidate for the solar cell application due its increased stability than Pb based perovskites. Finally, attempts have been made to fabricate a photovoltaic device using the as-prepared MBI to study its photoresponse. MBI was prepared in different solvents with various concentrations. We have measured efficiency 1.06% for DMSO solvent, 1.77% for DMF+DMSO solvent and finally the highest efficiency 1.87%, we have got with GBL+DMSO solvent. We concluded that GBL+DMSO solvent is best among all three solvents. Stability is also found best with GBL+DMSO solvent. Here we safely conclude that our objective of synthesis of MBI as an alternative to Pb based perovskite solar cell is verified successfully.