# Harnessing Functionalized Thioalkylated‐Cyclopentadithiophene Monolayers on NiOx for Two‐Step Fabricated Tin Perovskite Solar Cells

## TL;DR

Researchers developed new self-assembled monolayers to improve tin perovskite solar cells, achieving high efficiency and stability.

## Contribution

The novel use of CDTS-based SAMs on NiOx for TPSCs is introduced, achieving a record efficiency of 8.4%.

## Key findings

- CDTS-MN (1) TPSC devices achieved a power conversion efficiency of 8.41%.
- CDTS-based SAMs improved charge transfer and reduced interface recombination through S—S interactions.
- Single-crystal structures of CDTS-MN and CDTSb-MN confirmed the uniformity of the monolayers.

## Abstract

A new series of dithioalkylated‐methylidenyl‐cyclopentadithiophene (CDTS)‐based self‐assembled monolayers (SAMs), including CDTS‐MN (1), CDTSb‐MN (1b), CDTS‐CA (2), and CDTS‐PA (3), are developed for tin perovskite solar cells (TPSCs). Each SAM incorporates sulphur rich center CDTS and is complemented with various anchoring groups, such as methylenemalononitrile, cyanoacrylic acid, and cyano‐vinyl‐phosphonic acid in driving the formation of well‐crystallized and homogeneous perovskite layers using a two‐step fabrication process. Nickel Oxide (NiOx) combined with the newly designed CDTS‐based SAMs is utilized as the hole transport material (HTM). This configuration yielded an excellent power conversion efficiency (PCE) of 8.41% for CDTS‐MN (1) TPSC device as compared to CDTSb‐MN (1b; PCE: 8.03%), CDTS‐CA (2; PCE: 4.54%) and CDTS‐PA (3; PCE: 5.15%). Notably, single‐crystal structures of CDTS‐MN (1) and CDTSb‐MN (1b) are successfully obtained and systematically presented, demonstrating the uniformity of the CDTS monolayers formed on the ITO/NiOx substrate. The CDTS‐based SAM 1 excels in TPSCs by enhancing charge transfer and reducing interface recombination through strong π–π stacking and intermolecular S—S interactions. This report highlights the pioneering use of CDTS‐based organic sensitizers in TPSCs, representing the first documented application of CDTS‐based SAMs within the solar cell research field.

A new series of CDTS‐based self‐assembled monolayers on NiOx is developed, which enabled a high‐performance tin‐based perovskite solar cell with an efficiency of 8.4%. With strong intramolecular S···S interactions, the CDTS motif enhanced charge transport, improved efficiency, and gave excellent long‐term stability.