Development of Double Fence Porphyrins as Self-Assembled Monolayers for Tin-Based Perovskite Solar Cells

The MC-series porphyrins, incorporating a variety of thiophene- and dithiophene-containing donor groups, offer an effective passivation strategy to eliminate Sn²⁺ defects on the surface of tin perovskite. Additionally, the C(15) position of the porphyrin core is linked to various electron-accepting groups, such as 2,1,3-benzothiadiazole, 4-(2,3-diphenylquinoxalin-5-yl)benzoic acid and an indacenodithiophene unit connected to carboxylic acid or cyanoacrylic acid. These groups act as self-assembled monolayers (SAMs) on indium tin oxide (ITO) substrates for tin-based perovskite solar cells (TPSCs). This study is the first example to report the use of porphyrin as SAM for TPSCs. In the presence of SAMs, the devices achieved efficiencies in the following order: MC-4 (8.65%) > MC-3 (6.19%) > MC-2 (5.06%) > MC-1 (5.03%). The outstanding performance of the MC-4 device is attributed to its retarded charge recombination, increased hole mobility, and superior hole-extraction capability. This approach offers a promising pathway for further developing porphyrin-based TPSCs.