Charge transfer rates and electron trapping at buried interfaces of perovskite solar cells
Igal Levine, Amran Al‐Ashouri, Artem Musiienko, Hannes Hempel, Artiom Magomedov, Aida Drevilkauskaitė, Vytautas Getautis, Dorothee Menzel, Karsten Hinrichs, Thomas Unold, Steve Albrecht, Thomas Dittrich
Abstract
Identification of electronic processes at buried interfaces of charge-selective contacts is crucial for photovoltaic and photocatalysis research. Here, transient surface photovoltage (SPV) is used to study the passivation of different hole-selective carbazole-based SAMs. It is shown that transient SPV and transient photoluminescence provide complementary information on charge transfer kinetics and trapping/de-trapping mechanisms, and that trap-assisted non-radiative recombination losses originate from electron trapping at the SAM-modified ITO/perovskite interface. The hole transfer rates and the density of interface electron traps, obtained by fitting SPV transients with a minimalistic kinetic model, depended strongly on the SAM’s chemical structure, and densities of interface traps as low as 109 cm−2, on par with highly passivated c-Si surfaces, were reached for Me-4PACz, previously used in record perovskite/silicon tandem solar cells. The extracted hole transfer rate constants and interface trap densities correlated well with the corresponding fill factors and open-circuit voltages of high-efficiency solar cells.