Strong Performance Enhancement in Lead-Halide Perovskite Solar Cells through Rapid, Atmospheric Deposition of n-type Buffer Layer Oxides

TL;DR

This paper introduces a rapid atmospheric CVD method to deposit oxide buffer layers on lead-halide perovskites at higher temperatures, significantly improving solar cell efficiency and stability.

Contribution

The study demonstrates a novel atmospheric pressure CVD technique for depositing high-quality oxide layers at elevated temperatures on sensitive perovskites, enhancing device performance.

Findings

TiOx films grown in under 1 min without vacuum

Increased perovskite device efficiency by over 2%

Steady-state efficiency improved from 16.5% to 19.4% with SnOx layer

Abstract

Thin (approximately 10 nm) oxide buffer layers grown over lead-halide perovskite device stacks are critical for protecting the perovskite against mechanical and environmental damage. However, the limited perovskite stability restricts the processing methods and temperatures (<=110 C) that can be used to deposit the oxide overlayers, with the latter limiting the electronic properties of the oxides achievable. In this work, we demonstrate an alternative to existing methods that can grow pinhole-free TiOx (x = 2.00+/-0.05) films with the requisite thickness in <1 min without vacuum. This technique is atmospheric pressure chemical vapor deposition (AP-CVD). The rapid but soft deposition enables growth temperatures of >=180 {\deg}C to be used to coat the perovskite. This is >=70 {\deg}C higher than achievable by current methods and results in more conductive TiOx films, boosting solar cell efficiencies by >2%. Likewise, when AP-CVD SnOx (x ~ 2) is grown on perovskites, there is also minimal damage to the perovskite beneath. The SnOx layer is pinhole-free and conformal, which reduces shunting in devices, and increases steady-state efficiencies from 16.5% (no SnOx) to 19.4% (60 nm SnOx), with fill factors reaching 84%. This work shows AP-CVD to be a versatile technique for growing oxides on thermally-sensitive materials.