In a groundbreaking advancement for the field of perovskite solar cells (PSCs), researchers have unveiled a novel molecular design that significantly enhances device efficiency and stability. Traditional PSC technologies have struggled with achieving optimal hole transport efficiency due to the intrinsic limitations posed by hole-selective self-assembled monolayers (SAMs). While these SAMs have been promising in enhancing performance, their strong intermolecular interactions often lead to unwanted self-aggregation. This aggregation compromises their interfacial contact with the transparent conductive oxide (TCO) substrate, reducing the overall hole transport efficiency and stability of the solar cells. Addressing these challenges head-on, the latest study introduces a new class of bicarbazole-based dimeric molecular structures incorporating strategically placed amide units, enabling robust hydrogen-bonding networks both within individual molecules and at the interface with the TCO.
The ingenious molecular engineering of these dimeric SAMs employs amide groups acting as dual hydrogen-bond donors and acceptors, fostering a sophisticated network of hydrogen bonds. This network fosters a homogeneous molecular arrangement, which is crucial for achieving uniform energy landscape alignment at the hole-transport interface. By mitigating the issues related to self-aggregation, the newly designed SAMs form a more ordered and stable interfacial layer, which directly translates to minimized hole-transport loss. This achievement is critical because loss in hole transport often forms a bottleneck, limiting the maximum achievable power conversion efficiency (PCE) of PSCs.
Demonstrating the notable impact of this approach, the research team reports an impressive power conversion efficiency of 21.56% in perovskite solar cells with a wide bandgap of 1.77 eV. The device exhibits an open-circuit voltage (Voc) as high as 1.35 V and an exceptional fill factor (FF) reaching 85.76%. These parameters underscore the robust hole extraction and transport facilitated by the hydrogen-bonded dimeric SAM. Such figures not only represent significant improvements over previous state-of-the-art SAMs but also highlight the potential of hydrogen-bond-driven molecular design strategies to optimize interfacial energetics and charge dynamics in PSCs.
Extending the versatility of their approach, the researchers applied the same hydrogen-bond-engineered SAM to narrower bandgap (1.56 eV) perovskite solar cells. Here, the devices recorded an outstanding efficiency of 26.80%, which was further confirmed via rigorous certification, yielding a certified efficiency of 26.57% by current density–voltage (J–V) scans and an impressive steady-state output of 25.92% over 300 seconds. The stability represented by the steady-state output supports the assertion that the self-assembled hydrogen-bonding networks not only enhance initial performance but also contribute to the long-term operational stability of PSCs—a key consideration for practical applications.
Perhaps the most remarkable implication of this innovative molecular design emerges in the arena of all-perovskite tandem solar cells. Tandem architectures, integrating two sub-cells with complementary bandgaps, hold the promise of surpassing the Shockley-Queisser limit that constrains single-junction solar cells. Utilizing the newly developed bicarbazole dimeric SAMs, the team achieved a record power conversion efficiency of 30.19% in integrated all-perovskite tandem devices. The certification processes confirmed these outstanding results, with a certified efficiency of 29.38% via J–V scanning and a reliable steady-state output of 28.40% measured over 120 seconds. This efficiency benchmark situates these tandem solar cells at the forefront of photovoltaics innovation, showcasing the practical viability of hydrogen-bond network engineering in advancing solar technologies.
Delving into the molecular mechanics underlying this breakthrough, the role of amide-containing bicarbazole units is pivotal. The introduction of amide functionality serves a dual purpose: it modulates intermolecular spacing by forming internal hydrogen bonds and concurrently anchors the SAM to the TCO surface through hydrogen bonding with oxide species. This dual hydrogen-bonding role enhances both molecular self-assembly and adhesion to the substrate, crucially reducing defect sites at the interface where charge recombination commonly occurs. Eliminating such recombination centers is imperative for the efficient extraction of photogenerated holes and optimal device performance.
A key challenge addressed by this research involves the energy level alignment at the hole transport interface. Mismatched energy levels lead to barriers impeding charge extraction and increase the likelihood of recombination losses. The well-aligned energy levels facilitated by the ordered hydrogen-bond networks in the novel SAMs ensure efficient hole extraction, as evidenced by the enhanced open-circuit voltages achieved. This suggests that molecular ordering orchestrated by hydrogen bonding provides a new paradigm for interface engineering, beyond traditional approaches based on covalent surface modifications or doping strategies.
In addition to performance gains, the stability of perovskite solar cells under operational conditions remains a critical hurdle. PSCs typically suffer from interface degradation induced by environmental stressors such as moisture, heat, and UV exposure. The robust hydrogen-bonded structure of these SAMs improves interfacial stability by providing a durable protective layer that resists mechanical and chemical degradation. Consequently, this molecular design strategy could lead to solar cells with extended operational lifetimes, a pivotal advancement for commercial viability.
The broader implications of this study resonate well beyond perovskite photovoltaics. The concept of employing self-assembled monolayers with dual-function hydrogen-bonding motifs opens new avenues in organic electronics and optoelectronics, where interface control is paramount. This molecular design framework may be adapted to tailor interfaces in organic light-emitting diodes, photodetectors, and other semiconductor technologies requiring precise charge transport layers. The approach underscores the immense potential of supramolecular chemistry in revolutionizing device engineering.
Examining the fabrication process, the self-assembling nature of these bicarbazole dimeric molecules simplifies device manufacturing by avoiding complex deposition steps. Their solution processability and innate tendency for ordered assembly facilitate scalable production methods, potentially reducing fabrication costs while maintaining superior performance. This responsiveness to industrial scalability is a notable advantage, heralding a swift transition from laboratory breakthroughs to commercial solar module assembly lines.
Moreover, the modular design of these molecules offers tunability in optoelectronic properties. By varying the chemical environment around the amide units or tweaking the dimeric core structure, researchers could fine-tune hydrogen bonding strengths, molecular packing density, and energy level alignment. Such chemical versatility empowers targeted optimization strategies tailored to different perovskite compositions or device architectures, maximizing performance across diverse photovoltaic platforms.
The collaborative efforts of chemists, material scientists, and device engineers are evident in this multidisciplinary endeavor. Integrating insights from molecular design, interface physics, and device engineering highlights a holistic approach vital for pushing the frontiers of solar cell technologies. This breakthrough exemplifies how nuanced molecular engineering at the nanoscale can bring transformative advancements in renewable energy solutions.
Looking ahead, further exploration into the interplay between hydrogen-bond networks and defect passivation at the atomic level could unravel new strategies for mitigating one of the most persistent limitations—nonradiative recombination at interfaces. Advanced spectroscopic techniques and computational modeling will be instrumental in dissecting these interactions, paving the way for the rational design of next-generation hole-transport materials.
As the urgency for sustainable energy intensifies globally, innovations such as these herald an exciting future for photovoltaics. By bridging the gap between molecular chemistry and device performance, the research opens doorways towards more efficient, durable, and economically viable solar cells. The demonstrated synergies between molecular self-assembly and energy conversion efficiency position this work as a cornerstone in the evolving landscape of clean energy technologies.
In summary, the deployment of bicarbazole-based dimeric molecules embedded with amide units to form hydrogen-bonding networks has ushered in a new era for all-perovskite solar cell architectures. From marked improvements in single-junction PSC efficiencies to record-setting tandem device performances, this molecular engineering triumph addresses long-standing challenges structurally and electronically. The confluence of enhanced charge transport, interfacial stability, and fabrication scalability sketched in this pioneering study provides a robust blueprint for the next generation of photovoltaic innovations.
The potential scalability, combined with certified record efficiencies and resilience, lends confidence for broader adoption in commercial applications. Harnessing the power of hydrogen bonding through molecular design not only advances PSC technology but also enriches the fundamental understanding of interface phenomena critical across varied optoelectronic devices. As research efforts build on this milestone, the horizon for cost-effective and sustainable solar energy solutions looks exceptionally bright.
Subject of Research:
Perovskite solar cells and molecular interface engineering via self-assembled monolayers with hydrogen-bond networks.
Article Title:
Self-assembled molecules with hydrogen-bond networks enable efficient all-perovskite tandem solar cells.
Article References:
Wang, D., Liu, Z., Gao, ZW. et al. Self-assembled molecules with hydrogen-bond networks enable efficient all-perovskite tandem solar cells. Nat Energy (2026). https://doi.org/10.1038/s41560-026-01964-4
DOI:
https://doi.org/10.1038/s41560-026-01964-4
Tags: advancements in solar energy materialsamide groups in solar cellsdimeric molecular engineeringhole transport efficiency improvementshydrogen-bonded molecular structuresinnovative solar cell technologiesmolecular design for energy efficiencyperovskite solar cells enhancementreducing self-aggregation in SAMsself-assembled monolayers challengesstable interfacial layers in PSCsTCO interface optimization
