Optimizing grading profiles for enhanced photovoltaic performance in CsGeI_3-xBr_x perovskite devices

The present work explored the environment friendly all-inorganic Cs-based perovskite CsGeI_3-xBr_x as prime light active materials in the purposed PSC device. The purposed solar cell heterostructure simulated in SCAPS-1D at room temperature for the cell configuration FTO/ZnO/Graded CsGeI_3-xBr_x/Cu₂O/Au. Further, linear and parabolic grading performed along the depth of absorber CsGeI_3-xBr_x by changing the composition (x) of Br from 0 to 3 to enhance the PV performance of the purposed device. The impact of composition (x) variation from 0 to 3, thickness variation from 0.5 to 1.0 μm and bowing factor variation from 0 to 1 on the output parameters obtained under the linear and parabolic grading of the purposed PSC device was extensively investigated and comprehensively analyzed. The effects of series resistance, back contact metal work function and the overall device operating temperature were also extensively studied. The various hole and electron transport layers (HTLs and ETLs) are explored and investigated under both linear and parabolic grading conditions for selecting the appropriate and suitable one. The present detailed investigation and comprehensive analysis of the linear and parabolic graded outcome revealed the superior PV performance. The exceptionally impressive PCE ∼33.42 % at zero series resistance and room temperature condition delivered by the purposed device along with excellent PV parameters V_OC∼1.33 V, J_SC∼29.302 mA/cm², FF∼85.34 % for 1 μm thick CsGeI_3-xBr_x under the parabolic graded condition.