Recently, the research article titled “Highly efficient phenothiazine 5,5-dioxide-based hole transport materials for planar perovskite solar cells with a PCE exceeding 20%” was published in J. Mater. Chem. A, 2019,7, 9510-9516 (IF= 10.733). Jiangsu University was the first contribution institution, Prof. Huaming Li, Prof. Ming Cheng and Prof. Cheng Chen are co-corresponding authors.

　　One of the major challenges for further improvement of the efficiency of perovskite solar cells (PSCs) is the lack of sufficiently good hole transport materials (HTMs) to efficiently scavenge the photogenerated holes and aid the transport of the holes to the counter-electrode in the PSCs. Therefore, there is a great need to diversify the design of cost-effective and highly-efficient HTMs. Besides that, the fundamental understanding of structure-performance relationships for HTMs, such as how molecular configuration and heteroatoms in core building block impact the efficacy of HTMs, is still lagging. To address these needs, in this published paper, they reported two facilely synthesized phenothiazine 5,5-dioxide (PDO) core building block based HTMs. The research results demonstrate the oxidation of sulfur atom to sulfuryl and minor molecular engineering on N-substitution dramatically influenced the configuration and photovoltaic performance of relative HTMs. PSCs containing PDO2 as HTM show a very impressive PCE of 20.2%, which is higher than the Spiro-OMeTAD-based reference devices (19.8%).