Yuyan Dong

Abstract The bottom contact in perovskite solar cells (PSCs) is easy to cause deep trap states and severe instability issues, especially under maximum power point tracking (MPPT). In this study, sodium gluconate (SG) is employed to disperse tin oxide (SnO 2 ) nanoparticles (NPs) and regulate the interface contact at the buried interface. The SG‐SnO 2 electron transfer layer (ETL) enabled the deposition of pinhole‐free perovskite films in ambient air and improved interface contact by bridging effect. SG‐SnO 2 PSCs achieved an impressive power conversion efficiency (PCE) of 25.34% (certified as 25.17%) with a high open‐circuit voltage ( V OC ) exceeding 1.19 V. The V OC loss is less than 0.34 V relative to the 1.53 eV bandgap, and the fill factor (FF) loss is only 2.02% due to the improved contact. The SG‐SnO 2 PSCs retained around 90% of their initial PCEs after 1000 h operation (T 90 = 1000 h), higher than T 80 = 1000 h for the control SnO 2 PSC. Microstructure analysis revealed that light‐induced degradation primarily occurred at the buried holes and grain boundaries and highlighted the importance of bottom‐contact engineering.

Abstract All‐inorganic n‐i‐p perovskite solar cells (PSCs) using doped Spiro‐OMeTAD as hole transport material (HTM) suffer from photothermal stability due to ionic diffusion and radical‐induced degradation by the dopants. In this article, dopant‐free starlike molecule (N2, N2‐bis(4‐(bis(4‐methoxyphenyl)amino)phenyl)‐N5,N5‐bis(4‐methoxyphenyl)pyridine‐2,5‐diamine (BD)) is synthesized to engineer the stacking properties and delivered higher hole mobility than doped Spiro‐OMeTAD (3.2 × 10 −4 versus 1.76 × 10 −4 cm 2 V −1 s −1 ) as dopant‐free HTM. Starlike BD HTM has a twisted acceptor unit and strong dipole, forming crystalline and ordered packing film to ensure intramolecular charge transfer and improve mobility. The BD CsPbI 3 PSCs deliver the maximum efficiency of 19.19%, which is the highest performance for all‐inorganic PSCs based on dopant‐free HTMs. Meanwhile, the ordered molecules‐packing blocks the migration channel of I − ions to metal electrodes and improves the device stability. BD‐based devices maintain more than 93% and 80% of the initial efficiency after 85 °C storage for 35 days and maximum power point (MPP) tracking at 85 °C for 1000 h, respectively.

One common and traditional method of detecting stored-grain deterioration is by measuring grain temperature. Key to stored-grain temperature measurement by acoustic tomography is discussed. Grain is a highly absorbing acoustical medium, acts as an acoustical low-pass filter, accordingly acoustical signal distorts seriously in transmission. An acoustic-attenuation-property weighted generalized cross-correlation method (for short AAP-GCC) is proposed. Using BCC (basic cross-correlation), PHAT-GCS and AAP-GCS, the estimations of acoustical travel-time in a grain bin of 10m diameter were computer simulated under various sound wave paths and various signal-to-noise ratios. Simulation results show that for a short sound wave path, all the three methods can give good estimation, and BCC is the best since it is the simplest; for a long path, AAP overmatch BCC and PHAT, which indicates that AAP can repair the signal distortion due to sound attenuation effectively. Examples of estimation by AAP, BCC and PHAT are given.

Abstract The molecular aggregation state of organic hole conductors greatly influences charge collection of perovskite solar cells (PSCs). In this study, we optimize the core/periphery steric Cl‐substituent (W1, W2, W3) and regulate the aggregation state by molecular packing and interactions. It is demonstrated that W1 with Cl core‐substituent exhibits enhanced crystallization and strong intermolecular interactions in contrast to W2 with Cl sidechain‐substituent. Conversely, W3 with Cl substituent at both core and sidechain results in the most unfavorable molecular stacking. W1 exhibits high charge mobility and reinforced interfacial bonding, achieving a remarkable photovoltaic efficiency of 24.7%, outperforming the other two (W2's 23.9% and W3's 20.3%). Furthermore, W1‐ and W2‐PSCs retain 95.3% and 87.2% of their initial efficiency after 1,000 hours of maximum power point tracking (MPPT), respectively. This work provides fundamental insights into Cl‐substituent‐induced molecular aggregation behavior and offers a delicate approach for designing high‐performance organic hole semiconductors.

Abstract Perovskite's surface defects trigger deep level traps and energy misalignment, resulting in substantial interface recombination and energy loss in perovskite solar cells (PSCs). Herein, 9‐fluoreneacetic acid (FAA), a self‐assembled molecule (SAM), is employed to passivate the interface defects and modulate energy alignment. SAM modification reduces the defect density from 6.37 × 10 15 to 3.11 × 10 15 cm −3 and produces a p‐type surface with an upward band bending, thus constructing a well‐defined n‐i‐p heterojunction for efficient charge separation. Accordingly, the target PSC realizes 24.75% power conversion efficiency (PCE) and retains 92% for 1100 h during maximum power point tracking (MPPT) at room temperature. Furthermore, over 80% of initial PCE has been reserved after 2500 h aging in 25–30% relative humidity (RH). This SAM strategy is expected to enhance the efficiency and stability for n‐i‐p PSCs.