Lead (Pb) free (non-toxic) perovskite solar cells materials have attracted great interest in the commercialization of the photovoltaic devices. In this work, density functional theory (DFT) and linear response time-dependent within density functional theory (TDDFT) are used to simulate and investigate the effect of gold (Au) dopedPb-free double halide perovskite A2BB?X6(A = Cs; B = In, Au; B? = Sb; X = Cl) on the structural, electronic, and optical properties for perovskite solar cell application. On the structural properties, bond length and bulk modulus calculations show that the doped compound is more likely to resist deformation than the undoped compound. The calculated band structure for both materials (doped and undoped) reveals the presence of the Valence Band Maximum (VBM) and the Conduction Band Minimum (CBM) at around the same symmetry point which indicates a direct band gap nature (at ???? point). The band gap value for the initial compound (= 0.99 eV) agrees with published theoretical values. For the gold doped compound, the value of the band gap increased to a value of 1.25eV. The result of the optical properties shows that the Au-doped material has higher absorption coefficient, lower reflectivity and higher optical conductivity when compared with the initial, as such demonstrates better properties as a candidate for solar cell applications and in other optoelectronic devices.

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Biogas has been increasingly used in generating energy in the deregulated energy market. Biogas production has been identified as a sustainable approach to mitigating the effect of climate change and global warming. This work conducted a comparative study of biogas production from poultry waste (Chicken droppings) and banana peels under the same operating conditions. 100g of each sample was mixed with 200cm³ of water for poultry waste and 400cm³ for banana peels and loaded into four cylindrical digesters. Each container was shaken to ensure a homogenous mixture and fermentation. Biogas was measured using the water displacement method for 14 days at an average of 27.7oC. The pH, temperature, and concentration were observed to affect biogas production. Within 14 days, 1556cm3 and 755cm3 of biogas were produced for poultry waste and banana peels. This shows that poultry waste produces more biogas than banana peels. Hence, it can be deduced that poultry waste is potentially a more promising feedstock for biogas production than banana peels; and can provide an alternative energy source for the local community in place of the conventional fossil fuel source.

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