Effect of the substitution position and extending the conjugation in naphthalene-triphenylamine hole transport materials for perovskite solar cells

Abstract

The π-bridge of D-π-D hole transport materials have great effect on the performance of perovskite solar cells. In this work, firstly, we designed and prepared a series of facile D-π-D HTMs with naphthalene as π-bridge and triphenylamine derivatives as terminal units. The effect of substitution position on molecule and device properties are analyzed. It is noted that the molecule with triphenylamine terminal units located on the 2,6-position (H-2,6) exhibit better conjunction than other positions, leading to better device performance though it has inferior film morphology on perovskite layer. Furthermore, we prepared a new HTM through increasing the benzene units in the vertical direction (H-6,12). H-6,12 exhibits weaker π-conjugation ability compared with H-2,6. The devices with pristine H-2,6 show better performance compared with H-6,12 because of better hole extraction ability of H-2,6. Interestingly, H-6,12 shows better device performance after doped with TBP and Li-TFSI due to much improved hole extraction ability of doped H-6,12. Moreover, doped H-6,12 also exhibit comparable device performance with conventional spiro-OMeTAD.