Rui-Tao Li

Bio: Rui-Tao Li is an academic researcher from Qingdao University of Science and Technology. The author has contributed to research in topics: Perovskite (structure) & Doping. The author has co-authored 2 publications.

Reducing Defects Density and Enhancing Hole Extraction for Efficient Perovskite Solar Cells Enabled by π-Pb 2+ Interactions.

Abstract: Molecular doping is an of significance approach to reduce defects density of perovskite and to improve interfacial charge extraction in perovskite solar cells. Here, we show a new strategy for chemical doping of perovskite via an organic small molecule, which features a fused tricyclic core, showing strong intermolecular π-Pb 2+ interactions with under-coordinated Pb 2+ in perovskite. This π-Pb 2+ interactions could reduce defects density of the perovskite and suppress the nonradiative recombination, which was also confirmed by the density functional theory calculations. In addition, this doping via π-Pb 2+ interactions could deepen the surface potential and downshift the work function of the doped perovskite film, facilitating the hole extraction to hole transport layer. As a result, the doped device showed excellent efficiency of 21.41% with ignorable hysteresis. This strategy of fused tricyclic core-based doping provides a new perspective for the design of new organic materials to improve the device performance.

Indigo: A Natural Molecular Passivator for Efficient Perovskite Solar Cells

Abstract: Organic–inorganic hybrid lead halide perovskite solar cells have made unprecedented progress in improving photovoltaic efficiency during the past decade, while still facing critical stability challenges. Herein, the natural organic dye Indigo is explored for the first time to be an efficient molecular passivator that assists in the preparation of high‐quality hybrid perovskite film with reduced defects and enhanced stability. The Indigo molecule with both carbonyl and amino groups can provide bifunctional chemical passivation for defects. In‐depth theoretical and experimental studies show that the Indigo molecules firmly binds to the perovskite surfaces, enhancing the crystallization of perovskite films with improved morphology. Consequently, the Indigo‐passivated perovskite film exhibits increased grain size with better uniformity, reduced grain boundaries, lowered defect density, and retarded ion migration, boosting the device efficiency up to 23.22%, and ≈21% for large‐area device (1 cm2). Furthermore, the Indigo passivation can enhance device stability in terms of both humidity and thermal stress. These results provide not only new insights into the multipassivation role of natural organic dyes but also a simple and low‐cost strategy to prepare high‐quality hybrid perovskite films for optoelectronic applications based on Indigo derivatives.

Environmental‐Friendly Polymer for Efficient and Stable Inverted Perovskite Solar Cells with Mitigating Lead Leakage

Abstract: Although perovskite solar cells (PSCs) are on the road to industrialization, the operational stability under high efficiency still needs to be improved, and the water solubility of lead ions (Pb2+) will cause environmental pollution problems. Herein, it is successfully implanted an environment‐friendly (biodegradability) poly(butylene adipate‐coterephthalate) polymer (PBAT) into the perovskite film, which can passivate the uncoordinated Pb2+ and neutral iodine defects of the perovskite material because of the adequate carbonyl groups and benzene rings in PBAT polymer, thereby regulating the crystallization of perovskite film with lower trap density, inhibiting the nonradiative recombination and improving charge carrier transport. As a result, the polymer‐incorporated inverted PSCs achieve optimal conversion efficiencies of 22.07% (0.1 cm2) and 20.31% (1 cm2). Meanwhile, the incorporated device, after being encapsulated, exhibits a prominent improvement in operational stability of high‐efficiency device under maximum power point tracking and continuous one sunlight illumination, maintaining the initial efficiency of 80% for 3249 h. More importantly, the polymer network can protect Pb2+ from being dissolved by water and prevent nearly 98% of Pb2+ from leaking by directly immersing the polymer‐coated perovskite film in water. Environmental‐friendly molecules provide new hope for solving lead poisoning and improving device operational stability under high efficiency.

Highly Efficient Flexible Perovskite Solar Cells through Pentylammonium Acetate Modification with Certified Efficiency of 23.35%

Abstract: Among the emerging photovoltaic technologies, rigid perovskite solar cells (PSCs) have made tremendous development owing to their exceptional power conversion efficiency (PCE) of up to 25.7%. However, the record PCE of flexible PSCs (≈22.4%) still lags far behind their rigid counterparts and their mechanical stabilities are also not satisfactory. Herein, through modifying the interface between perovskite and hole transport layer via pentylammonium acetate (PenAAc) molecule a highly efficient and stable flexible inverted PSC is reported. Through synthetic manipulation of anion and cation, it is shown that the PenA+ and Ac− have strong chemical binding with both acceptor and donor defects of surface‐terminating ends on perovskite films. The PenAAc‐modified flexible PSCs achieve a record PCE of 23.68% (0.08 cm2, certified: 23.35%) with a high open‐circuit voltage (VOC) of 1.17 V. Large‐area devices (1.0 cm2) also realized an exceptional PCE of 21.52%. Moreover, the fabricated devices show excellent stability under mechanical bending, with PCE remaining above 91% of the original PCE even after 5000 bends.

Synergy Effect of a π‐Conjugated Ionic Compound: Dual Interfacial Energy Level Regulation and Passivation to Promote <i>V</i> _oc and Stability of Planar Perovskite Solar Cells

Abstract: Defects and energy offsets at the bulk and heterojunction interfaces of perovskite are detrimental to the efficiency and stability of perovskite solar cells (PSCs). Herein, we designed an amphiphilic π-conjugated ionic compound (QAPyBF4 ), implementing simultaneous defects passivation and interface energy level alignments. The p-type conjugated cations passivated the surface trap states and optimized energy alignment at the perovskite/hole transport layer. The highly electronegative [BF4 ]- enriched at the SnO2 interface featured desired band alignment due to the dipole moment of this interlayer. The planar n-i-p PSC had an efficiency of 23.1 % with Voc of 1.2 V. Notably, the synergy effect elevated the intrinsic endothermic decomposition temperature of the perovskite. The modified devices showed excellent long-term thermal (85 °C) and operational stability at the maximum power point for 1000 h at 45 °C under continuous one-sun illumination with no appreciable efficiency loss.

Self‐Organized Small Molecules in Robust MOFs for High‐Performance Perovskite Solar Cells with Enhanced Degradation Activation Energy

Abstract: A brand new strategy to improve the volatility and disordered arrangement of small organic molecule additives within doped perovskite solar cells through the construction of metal–organic frameworks (MOFs) is proposed. The Zn‐TTB, self‐assembling from Zn2+ and 1‐(triazol‐1‐ly)‐4‐tetrazol‐5‐ylmethyl)benzene (TTB), inherits and arranges triazole and tetrazole groups and forms a long‐chain structure surrounding metal nodes. The perovskite precursors grow along with the skeleton of Zn‐TTB and produce a macromolecular intermediate phase via the MOFs‐perovskite interconnection, subsequently forming superior perovskite films with enhanced stability with respect to molecular additives, as evidenced by in situ thermogravimetry‐Fourier transform infrared spectroscopy measurements. Thermal analyses suggest MOF‐doping increases degradation activation energies by up to >174.01 kJ mol–1 compared to the reference sample (162.45 kJ mol–1). Zn‐TTB‐modified devices exhibit promising efficiencies (up to 23.14%) and operational stability in unencapsulated state, even under constant solar light illumination.