The Importance of Pendant Groups on Triphenylamine‐Based Hole Transport Materials for Obtaining Perovskite Solar Cells with over 20% Efficiency

Abstract

Tremendous progress has recently been achieved in the field of perovskite solar cells (PSCs) as evidenced by impressive power conversion efficiencies (PCEs); but the high PCEs of >20% in PSCs has so far been mostly achieved by using the hole transport material (HTM) spiro-OMeTAD; however, the relatively low conductivity and high cost of spiro-OMeTAD significantly limit its potential use in large-scale applications. In this work, two new organic molecules with spiro[fluorene-9,9′-xanthene] (SFX)-based pendant groups, X26 and X36, have been developed as HTMs. Both X26 and X36 present facile syntheses with high yields. It is found that the introduced SFX pendant groups in triphenylaminebased molecules show significant influence on the conductivity, energy levels, and thin-film surface morphology. The use of X26 as HTM in PSCs yields a remarkable PCE of 20.2%. In addition, the X26-based devices show impressive stability maintaining a high PCE of 18.8% after 5 months of aging in controlled (20%) humidity in the dark.

Stable and High‐Efficiency Methylammonium‐Free Perovskite Solar Cells

“…The values of integrated current density for without MA PSCs were decreased from sample 0 to sample 0.2 gradually with increasing amount of PbBr 2 , and the value of integrated current density for with MA sample (R) was closed to best without MA sample (0.15). Comparing with the value of integrated current density and the short circuit current density ( J SC ), there was a little decreased mostly owing to the fact that the EQE measurements were measured at a single wavelength with much lower intensity than one‐sun irradiation . These results are consistent with the UV–vis and PL measurement.…”

Positional Effect of the Triphenylamine Group on the Optical and Charge‐Transfer Properties of Thiophene‐Based Hole‐Transporting Materials

“…Moreover, to achieve high‐performance hole‐transport properties, Sprio‐OMeTAD requires additional oxidizing dopants, which are usually harmful to the stability of PSCs . To replace the cost spiro‐OMeTAD molecule, experimental scientists developed lots of new and lower‐cost organic small HTMs . However, the development of these new materials often resulted from a great deal of experimental “trial‐and‐error” using organic synthetic methods rather than rational design.…”

Rational Design of Cyclopenta[2,1‐b;3,4‐b′]dithiophene‐bridged Hole Transporting Materials for Highly Efficient and Stable Perovskite Solar Cells

“…A wide number of reports on high efficiencies of PSCs with organic molecule‐based HTMs has been developed such as spiro‐type,,, truxene, triazatruxene, azulene, benzotrithiophene, carbazole‐, anthracene‐, and bimesitylenes‐based derivatives . Despite tremendous efforts have been made to develop small molecule‐based HTMs for PSCs, there were few reports to elucidate the correlations between the chemical structures of HTMs and the corresponding roles played in the photovoltaic devices …”