Science News: 2021 Adv. Funct. Mater., PCE 24.8%! Fullerene Interlayers Applied to Narrow-bandgap 4T All-perovskite Solar Cell
Advanced Functional Materials (IF 18.808) journal published the research results of Bahram Abdollahi Nejand, Ulrich W. Paetzold and others from Karlsruhe Institute of Technology, Germany in December 2021. Interface engineering is the key to high-performance perovskite solar cells (PSC). Although scientists have extensively studied Pb perovskite fullerene interlayers with a bandgap of >1.5 eV, they have rarely studied the role of fullerene interlayers in Sn-Pb hybrid narrow-bandgap (NBG) PSCs.
In this study, the research team used unexplored fullerene derivatives as the interlayers in the NBG PSC, and studied their effects on device performance and non-radiative recombination. The researchers added three fullerene derivative interlayers to the perovskite/ETL interface, including indene-C60-propionic acid butyl ester (IPB), indene-C60-propionic acid hexyl ester (IPH) and traditional PCBM. Studies have found that IPH provided a higher conduction band offset (CBO), thereby inhibiting the non-radiative recombination of charge-carrier-back-transfer. IPH is the most effective interlayer in NBG PSCs.
The research team used the sun simulator and quantum efficiency measuring instrument for analysis. The research results showed that the device with IPH interlayer exhibited the highest performance, with a short-circuit current density of 30.7 mA cm-2 and an open-circuit voltage loss reduced to 0.43 V. The decrease in open circuit voltage loss was attributed to the decrease in non-radiative recombination, including:
(1) Higher conduction band offset ≈0.2 eV (>0 eV) hindered the charge-carrier-back-transfer recombination.
(2) The density of traps at the perovskite/interlayer/C60 interface decreased, resulting in reduced trap-assisted recombination.
In addition, the IPH interlayer could enhance the charge extraction within the device, thereby significantly increased the short-circuit current density. Using a NBG device with an IPH intermediate layer, a power conversion efficiency (PCE) of 24.8% was achieved in a four-terminal (4T) all-perovskite tandem solar cell.
Keywords: Perovskite, PSC, Fullerene-Derivative Interlayers, Solar Simulator, Quantum Efficiency, Sun Simulator