Abstract
A new series of diacetylide-triphenylamine (DATPA) derivatives with five different alkyl chains in the para position, MeO, EtO, nPrO, iPrO and BuO, were synthesised, fully characterised and their function as hole-transport materials in perovskite solar cells (PSC) studied. Their thermal, optical and electrochemical properties were investigated along with their molecular packing and charge transport properties to analyse the influence of different alkyl chains in the solar cell parameters. The shorter alkyl chain facilitates more compact packing structures which enhanced the hole mobilities and reduced recombination. This work suggests that the molecule with the methoxy substituent (MeO) exhibits the best semiconductive properties with a power conversion efficiency of up to 5.63%, an open circuit voltage (Voc) of 0.83 V, a photocurrent density (Jsc) of 10.84 mA cm-2 and a fill factor of 62.3% in perovskite solar cells. Upon replacing the methoxy group with longer alkyl chain substituents without changing the energy levels, there is a decrease in the charge mobility as well as PCE (e.g. 3.29% for BuO-DATPA). The alkyl chain length of semiconductive molecules plays an important role in achieving high performance perovskite solar cells.
Highlights
A new series of diacetylide-triphenylamine (DATPA) derivatives with five different alkyl chains in the para position, methoxy substituent (MeO), EtO, nPrO, iPrO and BuO, were synthesised, fully characterised and their function as holetransport materials in perovskite solar cells (PSC) studied
In previous work reported by our group, a series of triphenylamine-based hole transport material (HTM) having two diacetylide-triphenylamine (DATPA)[27] moieties and varying redox potentials was prepared by a simple synthetic route which allows easy tuning of electrochemical and other properties through varying the substituent R groups
In the case of organic photovoltaics, studies have shown both increases and decreases in power-conversion efficiency through increasing the length of alkyl chains,[31,33,34,35] greater systematic understanding of this effect for HTMs in PSCs is important we report a series of new diacetylide-triphenylamine substituents HTM coded as EtO-DATPA, iPrO-DATPA, nPrO-DATPA and BuO-DATPA with similar optical and electrochemical properties to the MeO-DATPA studied before.[27]
Summary
Derivatives,[18,19,20] triazatruxenes,[21,22] azulenes,[23] and other related examples,[24,25] leading to efficiencies comparable with spiroOMeTAD and progress on the preparation methods and cost. In previous work reported by our group, a series of triphenylamine-based HTMs having two diacetylide-triphenylamine (DATPA)[27] moieties and varying redox potentials was prepared by a simple synthetic route which allows easy tuning of electrochemical and other properties through varying the substituent R groups. These materials were studied as HTMs in PSCs and showed promising properties in comparison with spiro-OMeTAD. Reaction conditions: (a) K2CO3, 18-crown-6, R-Br, DMF, 100 1C, 4 h, N2 (b) CuI, 1,10-phenantroline, KOH, MePh, 4-bromoaniline, N2, 120 1C; (c) C8H16Si, CuI, piperidine, (PPh3)2PdCl2, PPh3, PhMe, N2, 90 1C; (d) 1 M TBAF, DCM, rt, N2; (e) CuCl, TMEDA, molecular sieves, DCM, air
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