First principles calculations for photovoltaic and optoelectronic properties of pristine and doped-graphene

This study employed density functional theory (DFT) calculations within the CASTEP code to investigate the effects of boron (B) and beryllium (Be) doping on the structural and optoelectronic properties of graphene. The computational method involved geometry optimization using the (L-BFGS) algorithm, the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) exchange-correlation functional, and ultrasoft pseudopotential. Structural analysis revealed higher bond populations and enhanced structural stability in B-doped configurations compared to Be-doped systems, with B-single-doped configurations showing the highest bond population and shortest average bond length. The electronic properties revealed that increasing B-doping concentrations led to higher band gaps: B-single (0.191 eV), B-dual (0.387 eV) and B-tri (0.44 eV). In contrast, the Be-doped configuration exhibited higher band gaps that decreased with increasing doping: Be-single (0.60 eV), Be-dual (0.550 eV), and Be-tri-doped (0.420 eV), suggesting potential for enhanced carrier mobility. The optical analysis revealed redshifted absorption peaks for B-single-doped graphene, suitable for infrared optoelectronics, while higher B-doping concentrations induced blueshifts, enabling visible and UV applications. The Be-single doped displayed blue shifted peaks, while the Be-dual doped exhibited visible light absorption and the Be-tri-doped had extended absorption peaks in the infrared region, making them suitable for UV applications, and IR image sensors. Additionally, Be-tri-doped graphene exhibited a high potential for photovoltaics, displaying multiple peaks in the visible range (1.6-2.4 eV), thus providing broader absorption properties. These findings provide valuable insight for tailoring the properties of graphene through controlled B and Be doping for diverse optoelectronic applications. The study demonstrates that Be and B doping can induce band gaps in graphene up to 0.60 eV and 0.44 eV, respectively, meeting the requirements for graphene based ON/OFF transistors. Future research can explore modelling graphene-based heterostructures for next-generation optoelectronics, leveraging their high charge mobilities and tuneable band structures.