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Perovskite‐based tandem solar cells have demonstrated high potential for overcoming the Shockley–Queisser limit. Routine bandgap (RBG, ≈1.55 eV) perovskites have achieved a perfect balance between efficiency and stability. The narrow bandgap (NBG) candidates for RBG perovskite‐based tandem devices are very limited. Lead sulfide (PbS) colloidal quantum dots (CQDs) are a promising partner due to their broad absorption spectra. However, the efficiency of RBG perovskite/QD tandem devices still lags behind. Herein, efficient RBG perovskite/QDs four‐terminal tandem photovoltaics are successfully implemented through synergistic enhancement from transparent electrode and band alignment Engineering. For tin doped indium oxide (ITO) electrodes, their conductivity and near‐infrared transparency are leveraged using magnetron sputtering and reactive plasma deposition (RPD) methods. Furthermore, instead of traditional zinc oxide, aluminum‐doped zinc oxide (AZO) is developed to enhance the carrier extraction capability of PbS QD bottom cells. Based on the above enhancements, ≈0.95 eV PbS solar cells achieve a record efficiency of 14.14%. Integrated with the front semi‐transparent perovskite solar cells, the four‐terminal perovskite/QD tandem device reaches a record efficiency of 26.12%. The synergistic combination of the RBG perovskite and NBG QD devices provides promising prospects for tandem photovoltaics. [ABSTRACT FROM AUTHOR]

Large‐scale all‐perovskite tandem photovoltaic has raised more attention as the power conversion efficiency (PCE) of this device in a small area reaches 28%. However, the wide‐bandgap (WBG)‐perovskite (Cs0.2FA0.8Pb(I0.6Br0.4)3‐1.77 eV) fabrication on a large scale still faces difficulty in nucleation and crystallization control, leading to complicated intermediates and poor‐quality films. Through a systematic investigation of the vacuum‐assisted blade‐coated WBG perovskite film formation process, the origin for poor film quality is attributed to the numerous nucleation pathways under rapid vacuum pressure decrease, resulting in a mix in intermediates of (Cs,FA)2Pb3(I,Br)8·xNMP, δ‐FAPbI3·xNMP, and PbI2·xNMP. To solve this problem, a proper additive MACl is selected and added. By lowering the formation energy of intermediate ((Cs,FA)Pb(I,Br)3·MACl·xNMP), the nucleation and crystallization process is successfully modulated into a single way, resulting in a single‐orientation (100) film and an enhanced device performance of 16.75%, which is the champion PCE of blade‐coated 1.77 eV perovskite so far. [ABSTRACT FROM AUTHOR]

[Display omitted] • Firstly, we conducted a comprehensive investigation into the crystal facet, meticulously examining the crystal facet orientation and surface atomic density of the ITO and NiO surfaces, respectively. we revealed that NiO surface exhibits less crystal facet orientations and higher metal atom density compared to ITO, suggesting that sufficient chemical binding sites for SAMs are provided to facilitate the close-packed assembly of SAMs. • Secondly, we further consider the surface roughness of ITO and ITO/NiO surfaces, respectively. NiO nanocrystals effectively reduce the surface roughness of ITO, preventing the accumulation of SAMs in ITO valleys, and facilitating the uniform distribution of SAMs. • Thirdly, based on heating and vacuum pumping experiments, we confirmed that the adhesion of − OH on the NiO is much stronger than that on the bare ITO, providing more stable assembly sites for SAMs. • Owning to the above three advantages, a more uniform, thinner, and stronger adhesion SAMs were achieved on the ITO/NiO surface compared to ITO. Finally, utilizing vacuum-assisted technology, we successfully fabricated WBG PSCs with a PCE of 19.55 % at 0.09 cm2 and a PCE of 18.74 % at 1 cm2, which are located at the top level among > 1.75 eV WBG PSCs. NiO/self-assembled monolayer (SAM) double hole transport layers (HTLs) has become the mainstream choice in high-efficiency single-junction and tandem perovskite solar cells (PSCs). However, the underlying role of NiO in double HTLs from the microscale is not systematically revealed currently. Herein, we reveal that NiO plays an important role in inducing a more uniform and thinner SAM from three aspects. Firstly, compared with indium tin oxide (ITO), the NiO surface exposes less crystal facet orientations and a higher metal atom density, suggesting that sufficient chemical binding sites for SAMs are provided to facilitate the close-packed assembly of SAMs. Secondly, NiO modified ITO exhibits smaller surficial roughness and strongly bonded −OH, which is beneficial to the uniform distribution of SAMs and strong adhesion to the NiO surface. Utilizing the well-constructed SAM, we fabricate wide-bandgap (>1.75 eV) PSCs using vacuum-assisted technology and achieve an impressive photoelectric conversion efficiency of 19.55 %. These findings not only deepen the understanding of SAM assembly on substrates but also provide essential guidance for the future industrialization of PSCs. [ABSTRACT FROM AUTHOR]