Simple CsI doping outperforms complex organic additives in carbon-based perovskite solar cells.

Area of Science:

• Materials Science
• Renewable Energy
• Solid-State Chemistry

Background:

• Carbon-based, hole-transport-layer-free perovskite solar cells (C-PSCs) offer low cost and stability but suffer from poor film quality and high defect density.
• Cesium iodide (CsI) doping is underexplored in HTL-free C-PSCs, often yielding limited improvements without additional components.

Purpose of the Study:

• To investigate the effect of CsI incorporation on the performance and stability of dual-cation (MA/FA) HTL-free C-PSCs.
• To develop a facile and scalable method for enhancing C-PSC properties using CsI doping.

Main Methods:

• A one-step spin-coating process was used to incorporate CsI into MA/FA perovskite films without interlayers or additives.
• Structural, compositional, and optoelectronic properties of the CsI-doped films were analyzed.
• Device performance (PCE) and long-term operational stability were evaluated.

Main Results:

• CsI incorporation significantly improved perovskite crystallization quality and induced lattice contraction.
• Defect density, ion migration, and non-perovskite phase formation were suppressed, enhancing phase stability.
• The champion CsI-doped C-PSC achieved a power conversion efficiency (PCE) of 17.31%, a substantial increase from the control device's 13.25% and retained 73% PCE after 30 days.

Conclusions:

• Facile CsI doping via a one-step process is an effective strategy for enhancing the performance and stability of HTL-free C-PSCs.
• Inorganic cation engineering with CsI offers a promising route for developing high-performance, durable, and cost-effective perovskite solar cells.
• This method avoids complex interlayers or additives, making it suitable for scalable manufacturing.