# Heteroaryl derivatives for hole-transport layers improve thermal stability of perovskite solar cells

## TL;DR

This paper shows how adding heteroaryl compounds to solar cell layers improves their heat resistance and efficiency, making them more viable for real-world use.

## Contribution

The use of heteroaryl additives in Spiro-OMeTAD is novel for enhancing thermal stability and photovoltaic performance in perovskite solar cells.

## Key findings

- PSCs with 3-phenylpyridine and 2-phenylpyridine retained over 100% of initial efficiency after 2400 hours at 85°C.
- Outdoor testing showed 90% of initial voltage after 1570 hours with maximum-power point tracking.
- Additives minimized reactivity and void formation in the hole-transport layer.

## Abstract

The thermal stability of perovskite solar cells (PSCs) remains a critical challenge for their integration into power grid applications. Here, we report the thermally stable PSCs by employing heteroaryl additives in the Spiro-OMeTAD. These additives effectively control void formation in the hole-transport layer and minimize reactivity with the perovskite layer, significantly improving the thermal stability of PSCs at 85 °C. As a result, PSCs with 3-phenylpyridine and 2-phenylpyridine maintained 101% and 104% of their initial photoconversion efficiency after 2400 hours of 85 °C test, respectively. As an added benefit, photovoltaic performance achieved a photoconversion efficiency of 25%. Also, the outdoor test shows 90% of the initial power point voltage after 1570 hours with maximum-power point tracking, showing remarkable light and cycle stability. We revealed the mechanism of how the additive can improve the thermal stability of PSCs by comparing 36 heteroaryl derivatives and 60 additive combinations.

In this work, Kanda et al. utilize heteroaryl additives to substantially improve thermal stability of perovskite solar cells, maintaining over 100% of initial efficiency after 2400 hours of aging at 85 °C, in addition to concurrently achieving 25% conversion efficiency and strong outdoor durability.