Performance enhancement of CsPbI_3-xBr_x perovskite solar cells via graded bandgap and affinity engineering

Abstract

All inorganic cesium lead-based perovskite solar cells (PSCs) have gained attention as alternative absorbing materials owing to their exceptional thermal stability. However, these devices are suffer from transmission and thermalization losses. Therefore, a novel grading approach is used in CsPbI3-x Brx perovskite solar cell to reduce the transmission and thermalization losses by enhancing the cell's ability to capture a broad spectrum of light wavelengths and suitably accommodate the material's energy bandgap. In this work, the performance of CsPbI3-xBrx perovskite solar cell with graded bandgap (Eg) and affinity has been explored and analyzed using the simulation SCAPS-1D tool. Different compositions (x) are varied to adjust the bandgap of CsPbI3-xBrx with different grading profiles such as linear, parabolic and beta grading. The graded structure enhances the absorption wavelength range and carrier lifetime. However, it also leads to the redistribution of the electrical field within the device, promoting more effective charge separation and collection. By utilizing this approach, the impact of absorber thickness variations from (50 nm to 700 nm) is also studied and analyzed with respect to grading profiles. Initially, 16.75% power conversion efficiency (PCE) is obtained by calibrating the experimental CsPbI3-xBrx graded solar cell. Then, performance is further improved by adjusting the bandgap with grading profiles, optimizing ETLs/HTLs and achieving optimum PV parameters: short-circuit current density (JSC) of 20.50 mA/cm2, open-circuit voltage (VOC) of 1.35 V, fill factor (FF) of 84.15 % and PCE of 23.11%. The findings of the reported study would significantly provide a path for the development of graded PSC.

The effective prolongation of the excited-state carrier lifetime of CsPbI2Br with applying strain

“…11 Therefore, to achieve a balanced solution between phase stability and light-capturing ability, partial substitution of I ions with Br ions, forming the mixed halide perovskite CsPbI 3− x Br x ( x = 0–3), results in excellent thermal stability and ideal optoelectronic performance. 12…”