Synthesis Of Piperazine Derivates And Their Application As Hole-transporting Materials In PSCs

Triphenylamine(TPA)derivatives is currently the most widely used hole-transporting material(HTM)in perovskite solar cells.In this dissertation,a series of new HTMs(QTPA and BPZTPA series)with p-? conjugated structure have been synthesized,which were built up by piperazine derivates core connecting TPA donors.The structures of six HTMs and intermediates were characterized by NMR and MS.The photophysical properties,molecular energy levels,thermal properties and film properties as well as hole-transporting mobilities of these compounds were discussed.The results indicated that QTPA and BPZTPA series compounds show the maximum absorption peaks at 313 and 292 nm,and the emission peaks at 404~419nm and 436~460 nm with the maximum absorption peaks as the excited wavelength,respectively.In addition,the absorption spectra of their spin-coating thin films are broadened and red-shifted(6~14 nm).These compounds possess high decomposition temperature(370~458 °C)and glass transition temperature(73~147 °C),exhibiting excellent thermal stability.Their HOMO levels(-5.35~-5.20 eV)can match well with CH3NH3PbI3 and Au,which was favorable for photogenerated carriers dissociation and charge transfer at the interfaces.Moreover,their higher LUMO levels(-2.51~-2.00 eV)can reduce the recombination of electron from perovskite layer and hole from hole-transporting layer as an electron blocking layer in the PSCs.At room temperature,hole-drift mobilities of six compounds were between 10-4 and 10-3 cm2/(V s),which indicate good hole-transporting abilities.They showed stable amorphous states in film,exhibiting a good film formability.The perovskite solar cells,fabricated with QTPA and BPZTPA series compounds as HTMs,and the best HTM concentration was 10 mg/mL by optimizing the process conditions.The devices all achieved a power conversion efficiency(PCE)of exceeding 8%,with the best PCE of 10.36% by MeO-BPZTPA without using p-type dopant,which affords an open-circuit voltage(Voc)of 917.1 mV,a short-circuit current density(Jsc)of 16.89 mA/cm2 and a fill factor(FF)of 0.669.This result indicates that the p-? conjugated structure of HTMs can also also have high efficiency,which enrichs the type of the HTM applied in perovskite solar cells and possess good application prospect.