Universal Bottom Contact Modification with Diverse 2D Spacers for High‐Performance Inverted Perovskite Solar Cells. (20th June 2021) - Li, Jun
Abstract: Although the 2D spacer modification is widely studied in perovskite solar cells (PVSCs), the energy level alignment between the 2D/3D interfaces makes it unfavorable for top surface passivation in the inverted p‐i‐n device structure. To address this issue, the effect of bottom interface modification is studied with three representative 2D spacers, i.e., the Ruddlesden‐Popper 2D spacer, Dion‐Jacobson 2D spacer, and strong passivation 2D spacer, in inverted p‐i‐n PVSCs. After optimization, the PVSCs with these 2D spacer modifications universally exhibit the best efficiencies of ≈21.6%, which constitutes dramatic improvement compared to the control device (20.7%). By lifting off the perovskite layer, the optoelectronic properties of the bottom surface are studied, and the mechanism underlying the improved device performance is unveiled to be uniformly originated from the formation of 2D/3D heterojunction, where the cascade valence band facilitates the hole collection and electron back scattering field suppresses the charge recombination at the anode interface. Besides, the unencapsulated device retains 90% of initial efficiency after 30 days of storage in ambient air with a relative humidity of 30 ± 5%, indicating excellent stability against moisture and oxygen. This study provides insight into the bottom interface modification with diverse 2D spacers for high‐performance p‐i‐n structured PVSC devices. Abstract : This study develops a universal bottom interface modification method with diverse 2D spacers, which significantly enhance the device performance of inverted perovskite solar cells from 20.7% to 21.6%. The lift‐off method is used to directly study the change of optoelectronic properties at the bottom interface and unveils the formation of 2D/3D heterojunction as the general mechanism underlying the device performance enhancement.