Molecular designing of triphenylamine-based hole-transporting materials for perovskite solar cells

Abstract

To maximize the performance of perovskite solar cells (PSCs), controlling the hole mobility is of fundamental importance. In this regard, developing efficient hole transport materials (HTMs)is highly desirable in next-generation solar cells. Herein, several dopant-free HTMs, with the donor–acceptor-donor (D-A-D) architecture, are designed based on benzophenone and di (pyridine-3-yl) methanone as the acceptors and triphenylamine (TPA) as the donor. The correlation between electronic structure and hole transport property of the TPA-based HTMs were systematically investigated by tuning the connection between donor and acceptor (single vs. double bond) and also the substitution position of the methoxy groups (ortho, meta, and para). Our results from density functional theory calculations indicate that introducing the vinyl group as the connecting π-bridge can effectively increase the hole mobilities of the designed HTMs. Among the investigated compounds, the combination of benzophenone core acceptor with para-methoxy TPA terminals via the vinyl bridge, called p-TEBET, shows the most promising features and achieves excellent hole mobility (1.58 × 10-1 cm2 V−1 s−1) which is larger than that of spiro-OMeTAD as the most commonly used HTM. The results of the present computational study can be further employed in the process of synthesizing new HTMs with promising features in terms of proper energy alignment, stability, and hole mobility.