A groundbreaking study in the field of perovskite solar cells (PSCs) has unveiled an innovative molecular strategy that could redefine the trajectory of solar energy technology. Researchers from Dalian Jiaotong University, Dalian University of Technology, and the CAS Hefei Institutes, spearheaded by Professors Guozhen Liu, Zhihua Zhang, and Xu Pan, have developed a pioneering approach to address one of the most persistent challenges within PSCs—the buried electron-transport interface. Their state-of-the-art research, recently published in Nano-Micro Letters, marks a paradigm shift toward achieving highly efficient and durable perovskite solar cells suitable for both rigid and flexible applications.
Perovskite solar cells have captivated the scientific and engineering communities due to their exceptional photovoltaic properties paired with cost-effective manufacturing possibilities. However, despite rapid improvements over the past decade, the interface between the perovskite layer and the electron transport layer often remains a significant bottleneck. This “buried interface” harbors complex defects and suffers from mechanical stresses that detrimentally impact device efficiency and longevity. Unmitigated, these factors throttle carrier extraction and accelerate device degradation, representing a major hurdle to PSC commercialization.
The research team has introduced a novel self-regulating “bilateral anchoring” molecular design centered around squaric acid (SA), a unique four-membered cyclic compound featuring dual carboxylic acid groups. This molecular bridge promotes robust bonding on both sides of the interface: it forms strong hydrogen bonds with the tin oxide (SnO₂) electron transport layer while simultaneously coordinating with under-coordinated lead ions (Pb²⁺) within the perovskite layer. This one-molecule solution elegantly fortifies the interface against the physical and chemical instabilities that traditionally plague PSCs.
Critically, the SA molecule exhibits a self-transforming quasi-aromatic backbone that dynamically responds to thermal processing. Prior to treatment, PSCs endure residual tensile stresses upwards of 24.6 MPa, which predispose the perovskite lattice to microcrack formation upon heating or mechanical deformation. Remarkably, the adoption of SA converts these detrimental tensile forces into beneficial compressive stress, reaching approximately -17 MPa. This stress reversal not only preserves the structural integrity of the perovskite film but also significantly enhances durability under thermal cycling and prolonged operation.
Furthermore, detailed density functional theory (DFT) simulations conducted by the team reveal substantial increases in the formation energies of common perovskite defects such as formamidinium vacancies (V FA), iodide vacancies (V I), lead vacancies (V Pb), and oxygen vacancies (V O) upon SA bonding. This indicates an effective passivation of trap states, which translates to a dramatic reduction in nonradiative recombination losses within the device. Complementing this, space-charge-limited current (SCLC) measurements indicate the charge-carrier mobility in SA-modified perovskites nearly doubles, climbing from 3.22 × 10⁻³ to 5.88 × 10⁻³ cm² V⁻¹ s⁻¹, directly contributing to enhanced photovoltaic performance.
The practical impact of this molecular engineering is persuasive. PSCs incorporating the SA interlayer achieve record power conversion efficiencies (PCEs) of 25.50% for rigid devices and 24.92% for flexible variants, both demonstrating markedly reduced hysteresis effects. These performances not only rival but also surpass many existing PSC benchmarks, particularly considering the modest hysteresis values below 2%, which indicate stable and reliable charge extraction behavior.
Strengthening the case for commercial viability, the technique exhibits broad compatibility with industrial-scale deposition methods, including spin coating, blade coating, and slot-die coating on diverse substrates such as glass, polyethylene naphthalate (PEN), and stainless steel foils. This compatibility addresses a critical scalability challenge that often impedes the transition from laboratory-scale to pilot-line manufacturing. Notably, 1 cm² rigid perovskite modules fabricated using this method maintain impressive efficiencies exceeding 24%, signaling tangible progress toward large-area device integration.
Crucially, long-term stability tests underscore the robustness engendered by the SA interlayer. Unencapsulated perovskite films retain more than 90% of peak power output even after over 3,800 hours exposed to moderate humidity (45 ± 5% RH). Thermal aging at 85 °C for 528 hours results in only a minor 12% decline in efficiency, while continuous one-sun maximum power point tracking over 1,700 hours preserves approximately 88% of initial device performance. Flexible devices subjected to rigorous mechanical flexing endure 10,000 bending cycles at a 5 mm radius with less than 10% capacity loss, an achievement underscoring their potential for wearable and portable energy harvesting applications.
The researchers emphasize that the success of this self-regulated bilateral anchoring strategy not only stems from its defect passivation prowess but also its intrinsic ability to manage interfacial mechanical stresses—two fundamental challenges that previously limited the durability and efficacy of PSCs. By uniting these functionalities in a single-component molecule, they pave the way for future solar cells exhibiting both excellent power output and longevity under real-world conditions.
Anticipating the next stages of development, the research team is actively coordinating the translation of the SA interface modification technique to roll-to-roll manufacturing lines catering to flexible PEN substrates. Mini-module production at dimensions approaching 30 × 30 cm² has already commenced, and efforts are underway to secure IEC 61215 certification within two years, which would signify compliance with international reliability and safety standards for photovoltaic modules.
In the broader context of renewable energy innovation, this landmark work elevates squaric acid as a commercially viable, multifunctional interface engineering molecule that seamlessly integrates charge transport enhancement, defect passivation, stress alleviation, and compatibility with various fabrication techniques. It presents a compelling blueprint for achieving scaled-up, efficient, and stable perovskite photovoltaics, a critical leap toward widespread solar energy adoption.
Ultimately, the team’s contributions propel PSCs closer toward the coveted promise of affordable, high-performance solar technology ubiquitously deployable across diverse substrates and environments. The convergence of molecular design insight with practical engineering solutions exemplifies how interdisciplinary ingenuity catalyzes transformative advances in next-generation photovoltaics. The scientific community eagerly awaits forthcoming pilot-line results expected from the collaborative laboratories of Professors Liu, Zhang, and Pan, heralding a new dawn for durable, efficient, and flexible perovskite solar cells.
Subject of Research: Perovskite Solar Cells, Interface Engineering, Molecular Passivation
Article Title: Self-Regulated Bilateral Anchoring Enables Efficient Charge Transport Pathways for High-Performance Rigid and Flexible Perovskite Solar Cells
News Publication Date: 14-Jul-2025
Web References: 10.1007/s40820-025-01846-6
Image Credits: Haiying Zheng, Guozhen Liu, Xinhe Dong, Feifan Chen, Chao Wang, Hongbo Yu, Zhihua Zhang, Xu Pan
Keywords: Perovskite Solar Cells, Interface Engineering, Squaric Acid, Charge Transport, Defect Passivation, Mechanical Stress Management, Flexible Photovoltaics, Photovoltaic Stability
