Highly Efficient and Stable Perovskite Solar Cells Enabled by All-Crosslinked Charge-Transporting Layers

Despite the demonstrated high power conversion efficiency (PCE) of perovskite solar cells (PVSC), long-term stability of the device operated in humid environments under photo- and thermal stresses is still a serious concern prior to any commercialization. To provide possible solutions to overcome this hurdle, we have synthesized an n-type conjugated molecule, c-HATNA, that can be crosslinked as an electron-transporting layer (ETL) on top of the desired perovskites. By proper doping to increase its electron-transporting property, a high PCE of 18.21% can be obtained with respectable moisture and thermal stability without encapsulation. Moreover, this c-HATNA ETL can be used in conjunction with another crosslinkable hole-transporting layer, c-TCTA-BVP, to fabricate all-crosslinked charge-transporting layers (CTLs) for PVSCs and achieve 16.08% and 13.42% PCEs on rigid and flexible substrates, respectively. More importantly, the device with all-crosslinked CTLs showed impressive thermal stability in ambient environment: almost 70% of its initial PCE after being heated at 70°C for 300 hr. Solution-processable organic-inorganic hybrid perovskite materials have emerged as a very promising candidate for next-generation photovoltaic technology due to their superior semiconducting properties. Although the performance of perovskite solar cells (PVSCs) has already been demonstrated to rival those of the prevailing inorganic counterparts, the device's long-term stability under thermal, photo-, and moisture stresses has been raised as one major challenge before the commercialization of this technology. Here, we have designed and synthesized a crosslinkable n-type conjugated molecule, c-HATNA, to serve as the electron-transporting layer on top of the perovskite to improve photo-, moisture, and thermal stability of the fabricated PVSCs. This work has validated the method of incorporating facile crosslinkable charge transport layers to improve efficiency and ambient and thermal stability of resultant solar cells to benefit large-scale device fabrication. We have designed and synthesized a crosslinkable n-type conjugated molecule, c-HATNA. This c-HATNA electron-transporting layer can be used in conjunction with another crosslinkable hole-transporting layer, c-TCTA-BVP (recently reported by our group), to fabricate an all-crosslinked CTL for PVSC. Benefiting from the low-temperature crosslinking reactions, the derived cells can achieve high PCE of 16.08% and 13.42% on rigid and flexible substrates, respectively. The device with all-crosslinked CTLs showed impressive thermal stability in ambient environment without encapsulation.