Chen Weijie

J.-W. Yoo, S.-Y. Kwon, and co-workers introduce a highly conductive and environmentally stable organic transparent electrode (TE), laminated with graphene barrier, on page 7234. Structural, electrical, and barrier properties as well as operational and thermal stability of TEs are systematically investigated. The electrodes possess excellent operational and thermal stability by employing 2D carbon materials while maintaining high conductivity and mechanical flexibility.

MACl, as additive to the standard FAPbI₃ precursor solution, enables near-complete coverage perovskite film to stabilize the phase-pure black FAPbI₃ annealing at 100 °C. A partial substitution of FACl for FAI in precursor solution is used to grow FA perovskites with controllable chlorine doped fraction, which improves the performance of the planar perovskite solar cell.

A PbSe quantum dot solar cell with an efficiency of 7.22% and a fill factor of 62.4% is achieved by applying a CsPbBr₃ perovskite quantum dot back layer. The back layer can effectively suppress carrier recombination at the PbSe/Au interfaces, hence lead to significant improvement in open-circuit voltage and fill factor.

The synthesis and characterization of a series of novel small-molecule hole-transporting materials (HTMs) based on an anthra[1,2-b:4,3-b′:5,6-b′′:8,7-b′′′]tetrathiophene (ATT) core are reported. The new compounds follow an easy synthetic route and have no need of expensive purification steps. The novel HTMs are tested in perovskite solar cells and power conversion efficiencies (PCE) of up to 18.1% under 1 sun irradiation are measured. This value is comparable with the 17.8% efficiency obtained using 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene as a reference compound. Similarly, a significant quenching of the photoluminescence in the first nanosecond is observed, indicative of effective hole transfer. Additionally, the influence of introducing aliphatic alkyl chains acting as solubilizers on the device performance of the ATT molecules is investigated. Replacing the methoxy groups on the triarylamine sites by butoxy-, hexoxy-, or decoxy-substituents greatly improves the solubility of the compounds without changing the energy levels, yet at the same time significantly decreasing the conductivity as well as the PCE, 17.3% for ATT-OBu, 15.7% for ATT-OHex, and 9.7% for ATT-ODec.

A sulfur-rich polycyclic aromatic hydrocarbon with a flat and rigid π-conjugated structure endowed with triarylamine groups is synthesized for highly efficient perovskite solar cells. The influence of alkyl chains, often introduced to increase the solubility of the hole-transporting materials, is furthermore investigated. Efficiencies as high as 18.1% are obtained.