# Thermodynamically Reinforced Dual‐Interface 1D/3D Tin‐Lead Perovskite Heterostructure for Stable All‐Perovskite Tandem Solar Cells

## TL;DR

A new method using a π-conjugated additive improves the stability and efficiency of perovskite solar cells, enabling longer-lasting and more efficient tandem devices.

## Contribution

A π-conjugated ammonium salt is introduced to create a dual-interface 1D/3D perovskite heterostructure, enhancing stability and performance in tandem solar cells.

## Key findings

- The dual-interface 1D/3D perovskite heterostructure achieves a power conversion efficiency of 22.23% with a T98 lifetime beyond 1000 hours.
- All-perovskite tandem devices reach 28.50% efficiency and maintain a T90 lifetime of 600 hours.
- The 1D perovskitoid interphases effectively stabilize the Sn-I octahedral framework, blocking oxidative and ion-migration pathways.

## Abstract

Tin‐lead (Sn‐Pb) perovskite solar cells (PSCs) remain fundamentally constrained by the intrinsic instability of Sn2+ oxidation and uncontrollable crystallization, critically limiting their operational reliability in tandem architectures. Herein, this study strategically introduces a π‐conjugated ammonium salt, 4‐aminobenzamidine dihydrochloride, which in situ directs the formation of a dual‐interface one‐dimensional/three‐dimensional (1D/3D) perovskite heterostructure, thereby re‐engineering the Sn‐Pb perovskite lattice toward enhanced thermodynamic stability. The self‐assembled 1D perovskitoid with intermolecular π‐π stacking acts as nucleation‐directing templates to relieve tensile strain and intra‐/intergranular disorder. Simultaneously, the contiguous 1D perovskitoid interphases encapsulating the 3D bulk fortify the vulnerable Sn‐I octahedral framework, effectively obstructing oxidative and ion‐migration pathways. This dual stabilization strategy endows the Sn‐Pb PSCs with unprecedented structural resilience, achieving not only a high power conversion efficiency (PCE) of 22.23% but also a T98 operational lifetime beyond 1000 hours. Building upon this enhanced structural robustness, the derived 2‐terminal (2T) all‐perovskite tandem devices deliver a PCE of 28.50% and sustain a T90 lifetime of 600 hours, underscoring the central role of lattice stabilization in advancing all‐perovskite tandem photovoltaics.

A π‐conjugated diammonium additive is employed to engineer a dual‐interface 1D/3D perovskite heterostructure. π‐π stacking 1D perovskitoids  act as nucleation templates to relieve tensile strain and intra‐/intergranular disorder and then encapsulate the 3D bulk to fortify the Sn‐I octahedral framework. The all‐perovskite tandem devices based 1D/3D Sn‐Pb heterostructure achieved an efficiency of 28.50% and a T90 operational lifetime of 600 hours.