Organic-inorganic hybrid material for hole transport in inverted perovskite solar cells.

Hole mobility is critical to the power conversion efficiencies of perovskite solar cells (PSCs). Organic small-molecule hole-transporting materials (HTMs) have attracted considerable interest in PSCs due to their structural flexibility and operational durability, but they suffer from modest hole mobility. On the other hand, inorganic HTMs with good hole mobility are inflexible in structural variation and exhibit unsatisfactory cell efficiency. In this study, a ligand BT28 and its zinc-based coordination complex BTZ30 were synthesized, characterized, and investigated as HTMs for PSC applications. The mixed-halide perovskites can be grown uniformly with large crystalline grains on both HTMs, which exhibit similar optical and electrochemical properties. However, it was discovered that the BTZ30-based solar cell exhibited an open-circuit voltage of 1.0817 V and a high short-circuit current density of 23.1392 mA cm-2 with a champion power conversion efficiency of close to 20 %. The performance difference between the two HTMs can be attributed to the difference in their hole mobilities, which is 63.31 % higher for BTZ30 than BT28. The comparison of non-metal and metal HTMs revealed the importance of considering hybrid structures to overcome some shortcomings associated with organic and inorganic HTMs and achieve high-performance PSCs.

Heterocyclic Functionalized Donor-Acceptor Hole-Transporting Materials for Inverted Perovskite Solar Cells.

Hole transport materials (HTMs) with appropriate energy levels and comprehensive passivation effects help to obtain highly efficient and stable perovskite solar cells (PSCs). Electron-deficient character-induced HTMs can generate varying energy level alignments near the HTM/perovskite interface. Herein, we report the synthesis and investigation of two new dipolar HTMs, WWC103 and WWC105, based on 2-(1,1-dicyanomethylene)rhodamine and 4-cynophenylacetonitrile acceptors, enabling high-efficiency mixed-cation mixed-halide perovskite solar cells. Apart from having different acceptors, these HTMs are built on a heterocyclic frame, which can provide passivation effects and improve the morphology of the perovskite layer. As a result, these dopant-free HTM-based solar cells show a high open-circuit voltage and good power conversion efficiency. Among both, the solar cell based on the HTM with 2-(1,1-dicyanomethylene)rhodamine exhibits a high open-circuit voltage of 1.09 V with a champion power conversion efficiency of over 20.51%. The improved performance of WWC103 over WWC105 (19.74%) is attributed to the new acceptor, which, in addition to providing good energy-level alignments and hole mobility, also holds the ability to passivate the defects. The findings suggest a new acceptor unit for constructing dopant-free HTMs for efficient PSCs.