Multifunctional Two-Dimensional Benzodifuran-Based Polymer for Eco-Friendly Perovskite Solar Cells Featuring High Stability

Customized Multifunctional Additive Regulates 1.67 eV-Wide-Bandgap Perovskite Crystallization for Four-Terminal Perovskite/Silicon Tandem Solar Cells

Wide-bandgap (WBG) perovskite solar cells (PSCs, Eg > 1.6 eV), serving as the top cell in perovskite/silicon tandem solar cells (PSTSCs), play an indispensable role in absorbing high energy photons and increasing overall efficiency. However, WBG PSCs often suffer from severe light-induced phase segregation and significant non-radiative recombination losses due to uncontrolled rapid crystallization. Here, polyfluoride molecular additives are designed and incorporated via (diacetoxyiodo)benzene into WBG perovskite, to regulate crystallization process of perovskite films and thereby reduce defects. (Bis(trifluoroacetoxy)iodo)benzene (BTFIB) can passivate uncoordinated lead ions and iodide vacancies, thereby inhibiting phase separation caused by iodide migration and reducing non-radiative recombination loss during charge transport. Moreover, the introduction of BTFIB can effectively moderate the film formation process and confer excellent hydrophobic properties to the films. Consequently, BTFIB-based 1.67 eV-WBG perovskite devices yield a champion efficiency of 23.05% (certified efficiency of 22.21%), enabling a 31.20% efficiency in four-terminal PSTSCs, along with excellent open-circuit voltage of 1.246 V and fill factor of 85.34%. After 2500 h of aging in a glovebox, the device retained 80% of its initial efficiency.

Crystallization Kinetics of Perovskite Films by a Green Mixture Antisolvent for Efficient NiOx-Based Inverted Solar Cells

Environment-friendly antisolvents are critical for obtaining highly efficient, reproducible, and sustainable perovskite solar cells (PSCs). Here, we introduced a green mixture antisolvent of ethyl acetate-isopropanol (EA/IPA) to finely regulate the crystal grain growth and related film properties, including the morphology, crystal structure, and chemical composition of the perovskite thin film. The IPA with suitable content in EA plays a key role in achieving a smooth and compact high-quality perovskite thin film, leading to the suppression of film defect-induced nonradiative recombination. As a result, the PSCs based on the EA/IPA (5:1) antisolvent showed a power conversion efficiency of 22.9% with an open-circuit voltage of 1.17 V.

Hole-Transport Management Enables 23%-Efficient and Stable Inverted Perovskite Solar Cells with 84% Fill Factor

NiOx-based inverted perovskite solar cells (PSCs) have presented great potential toward low-cost, highly efficient and stable next-generation photovoltaics. However, the presence of energy-level mismatch and contact-interface defects between hole-selective contacts (HSCs) and perovskite-active layer (PAL) still limits device efficiency improvement. Here, we report a graded configuration based on both interface-cascaded structures and p-type molecule-doped composites with two-/three-dimensional formamidinium-based triple-halide perovskites. We find that the interface defects-induced non-radiative recombination presented at HSCs/PAL interfaces is remarkably suppressed because of efficient hole extraction and transport. Moreover, a strong chemical interaction, halogen bonding and coordination bonding are found in the molecule-doped perovskite composites, which significantly suppress the formation of halide vacancy and parasitic metallic lead. As a result, NiOx-based inverted PSCs present a power-conversion-efficiency over 23% with a high fill factor of 0.84 and open-circuit voltage of 1.162 V, which are comparable to the best reported around 1.56-electron volt bandgap perovskites. Furthermore, devices with encapsulation present high operational stability over 1,200 h during T90 lifetime measurement (the time as a function of PCE decreases to 90% of its initial value) under 1-sun illumination in ambient-air conditions.