Evident Enhancement of Efficiency and Stability in Perovskite Solar Cells with Triphenylamine-Based Macromolecules on the CuSCN Hole-Transporting Layer

The CuSCN-containing perovskite solar cells (PSCs) are presently of great research focus due to the high carrier mobility and well-aligned work function of the CuSCN hole-transporting layer. The improvement of photovoltaic performance and stability is still an important subject in the practical applications of CuSCN-containing PSCs. Herein, a facile approach to improve the efficiency and stability of CuSCN-containing PSCs is developed by spin-coating the triphenylamine-based macromolecules between the CuSCN hole-transporting layer and metallic electrode, such as linear macromolecule poly-TPD and branched macromolecule CRA-TPA. The maximum power conversion efficiency (PCE) of CuSCN-containing PSCs is increased by linear triphenylamine-based macromolecule poly-TPD to 10.36% while the PCE value of CuSCN-containing PSCs, being modified by branched triphenylamine-based macromolecule CRA-TPA, reaches up to 11.97%. Evidently, the PCE values are nearly two times higher than 5.95% of CuSCN-containing control device. The photovoltaic improvement of macromolecule-modified CuSCN-containing PSCs is mainly caused by the strong hole-transporting capacity of triphenylamine-based macromolecules inducing the reduction of charge recombination, which is derived from the reduced potential barrier of hole transportation including the flatness and coverage improvement in the triphenylamine-based macromolecular functional layer. In addition, the stability of macromolecule-modified CuSCN-containing PSCs is significantly improved due to the protection of triphenylamine-based macromolecular layer on the perovskite film, so that the unencapsulated macromolecule-modified CuSCN-containing PSC device can keep over 70–80% of initial PCE value after 20-day exposure under ambient environment (relative humidity (RH) = 50%, 25°C). This work provides a facile approach to enhance the efficiency and stability of CuSCN-containing PSCs through the modification of triphenylamine-based macromolecules between the CuSCN hole-transporting layer and metallic electrode.