Passivation of the Buried Interface via Preferential Crystallization of 2D Perovskite on Metal Oxide Transport Layers

Abstract

The open‐circuit voltage (Voc) of perovskite solar cells is limited by non‐radiative recombination at perovskite/carrier transport layer (CTL) interfaces. 2D perovskite post‐treatments offer a means to passivate the top interface; whereas, accessing and passivating the buried interface underneath the perovskite film requires new material synthesis strategies. It is posited that perovskite ink containing species that bind strongly to substrates can spontaneously form a passivating layer with the bottom CTL. The concept using organic spacer cations with rich NH2 groups is implemented, where readily available hydrogens have large binding affinity to under‐coordinated oxygens on the metal oxide substrate surface, inducing preferential crystallization of a thin 2D layer at the buried interface. The passivation effect of this 2D layer is examined using steady‐state and time‐resolved photoluminescence spectroscopy: the 2D interlayer suppresses non‐radiative recombination at the buried perovskite/CTL interface, leading to a 72% reduction in surface recombination velocity. This strategy enables a 65 mV increase in Voc for NiOx based p–i–n devices, and a 100 mV increase in Voc for SnO2‐based n–i–p devices. Inverted solar cells with 20.1% power conversion efficiency (PCE) for 1.70 eV and 22.9% PCE for 1.55 eV bandgap perovskites are demonstrated.

Buried Interface Modification in Perovskite Solar Cells: A Materials Perspective

“…High GUA concentration leads to reduced J sc and FF as a result of the parasitic absorption and the insulating nature of wide bandgap 2D layers. [ 171 ]…”

“…b) Structural model and corresponding schematics of crystallization process for films with different GUA concentrations on NiO x substrate. Reproduced with permission [171]. Copyright 2021, John Wiley and Sons.…”

Roles of Long‐Chain Alkylamine Ligands in Triple‐Halide Perovskites for Efficient NiOx‐Based Inverted Perovskite Solar Cells

“…However, inorganic hole-transport-layer (HTL) NiO x -based inverted planar PSCs have been troubled by severe open-circuit voltage (V oc ) and fill factor (FF) loss attributed to the charged defects at the film surface, buried interface, and GBs of the perovskite bulk layer. [14][15][16][17] To overcome these defects, achieving a high-quality perovskite film and its defect passivation is critical. Thus, tremendous efforts have been dedicated toward minimizing the perovskite GBs and surface defects by additive and surface engineering.…”

1,8‐Octanediamine Dihydroiodide‐Mediated Grain Boundary and Interface Passivation in Two‐Step‐Processed Perovskite Solar Cells

“…[13][14][15] Lots of research has been reported on the investigation of the highly crystalline film formation and its post-treatment, to passivate the interface for the improved device performance. [16][17][18][19][20] You and co-workers optimized the PbI 2 content and developed the PEAI top-surface passivation route. [21,22] In contrast, Lu et al doped the A-site of perovskite by incorporating GA þ and reported high-crystalline perovskite films with high efficiency.…”