Self-Polymerized Spiro-Type Interfacial Molecule toward Efficient and Stable Perovskite Solar Cells.

In the pursuit of highly efficient perovskite solar cells, spiro-OMeTAD has demonstrated recorded power conversion efficiencies (PCEs), however, the stability issue remains one of the bottlenecks constraining its commercial development. In this study, we successfully synthesize a novel self-polymerized spiro-type interfacial molecule, termed v-spiro. The linearly arranged molecule exhibits stronger intermolecular interactions and higher intrinsic hole mobility compared to spiro-OMeTAD. Importantly, the vinyl groups in v-spiro enable in situ polymerization, forming a polymeric protective layer on the perovskite film surface, which proves highly effective in suppressing moisture degradation and ion migration. Utilizing these advantages, poly-v-spiro-based device achieves an outstanding efficiency of 24.54 %, with an enhanced open-circuit voltage of 1.173 V and a fill factor of 81.11 %, owing to the reduced defect density, energy level alignment and efficient interfacial hole extraction. Furthermore, the operational stability of unencapsulated devices is significantly enhanced, maintaining initial efficiencies above 90 % even after 2000 hours under approximately 60 % humidity or 1250 hours under continuous AM 1.5G sunlight exposure. This work presents a comprehensive approach to achieving both high efficiency and long-term stability in PSCs through innovative interfacial design.

A Multifunctional Dye Molecule as the Interfacial Layer for Perovskite Solar Cells.

In perovskite solar cells (PSCs), defects in the interface and mismatched energy levels can damage the device performance. Improving the interface quality is an effective way to achieve efficient and stable PSCs. In this work, a multifunctional dye molecule, named ThPCyAc, was designed and synthesized to be introduced in the perovskite/HTM interface. On one hand, various functional groups on the acceptor unit can act as Lewis base to reduce defect density and suppress nonradiative combinations. On the other hand, the stepwise energy-level alignment caused by ThPCyAc decreases the accumulation of interface carriers for facilitating charge extraction and transmission. Therefore, based on the ThPCyAc molecule, the devices exhibit elevated open-circuit voltage and fill factor, resulting in the best power conversion efficiency (PCE) of 23.16%, outperforming the control sample lacking the interface layer (PCE = 21.49%). Excitingly, when attempting to apply it as a self-assembled layer in inverted devices, ThPCyAc still exhibits attractive behavior. It is worth noting that these results indicate that dye molecules have great potential in developing multifunctional interface materials to obtain higher-performance PSCs.

Synergistic Optimization of Buried Interface by Multifunctional Organic-Inorganic Complexes for Highly Efficient Planar Perovskite Solar Cells.

For the further improvement of the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs), the buried interface between the perovskite and the electron transport layer is crucial. However, it is challenging to effectively optimize this interface as it is buried beneath the perovskite film. Herein, we have designed and synthesized a series of multifunctional organic-inorganic (OI) complexes as buried interfacial material to promote electron extraction, as well as the crystal growth of the perovskite. The OI complex with BF4- group not only eliminates oxygen vacancies on the SnO2 surface but also balances energy level alignment between SnO2 and perovskite, providing a favorable environment for charge carrier extraction. Moreover, OI complex with amine (- NH2) functional group can regulate the crystallization of the perovskite film via interaction with PbI2, resulting in highly crystallized perovskite film with large grains and low defect density. Consequently, with rational molecular design, the PSCs with optimal OI complex buried interface layer which contains both BF4- and -NH2 functional groups yield a champion device efficiency of 23.69%. More importantly, the resulting unencapsulated device performs excellent ambient stability, maintaining over 90% of its initial efficiency after 2000 h storage, and excellent light stability of 91.5% remaining PCE in the maximum power point tracking measurement (under continuous 100 mW cm-2 light illumination in N2 atmosphere) after 500 h.

Glucose and Its Derivatives as Interfacial Materials for Inverted Organic Solar Cells.

Glucose, a widely distributed biomaterial in nature, is presented as a new cathode interfacial material for highly efficient inverted organic solar cells. The interactions between glucose and the indium tin oxide (ITO) substrate as well as the formation mechanisms of the glucose interlayer were investigated by molecular dynamics simulation and relevant experimental tests. The results revealed that the In-OH coordination between the oxygen atom of glucose and the indium of ITO is the key factor for the formation of interfacial dipoles, thereby reducing the work function of the ITO cathode for efficient charge transfer. With PM6:Y6 as the active layer, the power conversion efficiency (PCE) of the organic solar cells was significantly increased from 1.99 to 15.42% after ITO was modified by a glucose interlayer through the traditional spin-coating method. More importantly, glucose can be adsorbed on the ITO surface by a simple immersion process, and the devices based on the modified ITO by immersed glucose achieved a PCE of 14.48%, which is comparable to that of the traditional spin-coating method. Furthermore, we found that the OSCs with the ITO cathodes modified with glucose derivatives including sorbitol and sodium gluconate by different preparation methods also exhibited high performance. The overall performance of the devices with ITO modified by a simple and low-cost immersion method can be maintained at more than 93% of that prepared with the traditional spin-coating method. The results demonstrated that low-price glucose and its derivatives are good candidates as ITO interlayer materials for OSCs, and the effectiveness of the immersion process paves a way for simplifying the manufacture of low-cost and large-area organic solar cells.

Doping of fullerenes via anion-induced electron transfer and its implication for surfactant facilitated high performance polymer solar cells.

Simple and solution-processible tetrabutyl-ammonium salts (TBAX) can dope fullerene and its derivatives to achieve conductive thin films (σ as high as 0.56 S/m). The electron transfer between the anions of TBAXs and n-type semiconductors induces doping without encountering any harsh activation. These provide valid support for the surfactant interfacial doping of fullerene in polymer solar cells for enhanced device performance.