Halogen‐Bonded Hole‐Transport Material Suppresses Charge Recombination and Enhances Stability of Perovskite Solar Cells

Abstract

Interfaces play a crucial role in determining perovskite solar cells, (PSCs) performance and stability. It is therefore of great importance to constantly work toward improving their design. This study shows the advantages of using a hole‐transport material (HTM) that can anchor to the perovskite surface through halogen bonding (XB). A halo‐functional HTM (PFI) is compared to a reference HTM (PF), identical in optoelectronic properties and chemical structure but lacking the ability to form XB. The interaction between PFI and perovskite is supported by simulations and experiments. XB allows the HTM to create an ordered and homogenous layer on the perovskite surface, thus improving the perovskite/HTM interface and its energy level alignment. Thanks to the compact and ordered interface, PFI displays increased resistance to solvent exposure compared to its not‐interacting counterpart. Moreover, PFI devices show suppressed nonradiative recombination and reduced hysteresis, with a Voc enhancement of ≥20 mV and a remarkable stability, retaining more than 90% efficiency after 550 h of continuous maximum‐power‐point tracking. This work highlights the potential that XB can bring to the context of PSCs, paving the way for a new halo‐functional design strategy for charge‐transport layers, which tackles the challenges of charge transport and interface improvement simultaneously.

Realizing High‐Efficiency Perovskite Solar Cells by Passivating Triple‐Cation Perovskite Films

“…PCE reverse and PCE forward represent PCE under reverse scan and forward scan, respectively. [ 39,40 ] The reduced H‐index (4.1%) for the KTN5‐passivated PSC demonstrated more effective hole extraction and suppressed recombination as compared with the control device. [ 41 ] To verify the accuracy of the J sc measurement in the J‐V curve, the incident photon‐to‐electron conversion efficiency (IPCE) was tested, and the spectrum is shown in Figure 2b.…”

Composited Film of Poly(3,4-ethylenedioxythiophene) and Graphene Oxide as Hole Transport Layer in Perovskite Solar Cells

“…As shown in Figure 4, after ten-days placement, the PCE of spiro-OMeTAD-based solar cells decreased to 75% of the initial value, while the PCE of PEDOT-GO-based solar cells still maintained 90% of the initial value. As an approximation, the time at which the efficiency has degraded to 80% of the initial value was denoted as T s80 [30]. We can observe that the T s80 of spiro-OMeTAD-based solar cells was about 5 days, while it needed more than 10 days for that of PEDOT-GO-based solar cells.…”

Halogen Bonding in Perovskite Solar Cells: A New Tool for Improving Solar Energy Conversion

“…[48] This concept was later on further developed by the same group,w ho obtained enhanced stability and performance of the devices by directly incorporating in the hole transport layer (HTL) XB-donor groups able to interact with the perovskite. [49] Thanks to the presence of XB,t he HTL can form amore ordered and compact layer, resulting in astronger interfacial dipole,reduced energetic offset for hole transport, and suppression of recombination processes.T he improved interface also increased the resilience against moisture and solvent, affording outstanding operational stability with ap rojected lifetime more than two-fold the standard devices. [50] 3.5.…”