Self-assembled monolayers (SAMs) have displayed unpredictable potential in efficient perovskite solar cells (PSCs). Yet most of SAMs are largely suitable for pure Pb-based devices, precisely developing promising hole-selective contacts (HSCs) for Sn-based PSCs and exploring the underlying general mechanism are fundamentally desired. Here, based on the prototypical donor-acceptor SAM MPA-BT-BA (BT), oligoether side chains with different length (i.e., methoxy, 2-methoxyethoxy, 2-(2-methoxyethoxy)ethoxy group) were custom-introduced on the benzothiadiazole unit to produce the target SAMs with acronyms MPA-MBT-BA (MBT), MPA-EBT-BA (EBT), and MPA-MEBT-BA (MEBT), respectively, and acting as HSCs for efficient Sn-Pb PSCs and all-perovskite tandems. The introduction of oligoether side chains enables HSCs effectively accelerate hole extraction, regulate the crystal growth and passivate surface defects of Sn-Pb perovskites. In particular, benefiting from the enhanced Sn-Pb perovskite film quality and the suppressed interfacial non-radiative recombination losses, EBT-tailored LBG devices yield a champion efficiency of 23.54%, enabling 28.61% efficient monolithic all-perovskite tandems with an impressive VOC of 2.155 V and excellent operational stability as well as 28.22%-efficiency 4-T tandems. The development of hole-selective contacts for Sn-based perovskite solar cells is highly desirable. Here, the authors report self-assembled monolayers with oligoether side chains on the benzothiadiazole unit and achieve an efficiency of 28.61% for operationally stable all-perovskite tandems.

Wide-bandgap (WBG) perovskite solar cell (PSC) plays a pivotal role as the top subcell in all-perovskite tandem solar cells (TSCs), facilitating the absorption of high-energy photons and affording a large open-circuit voltage (VOC). Nonetheless, the stability and efficiency of WBG PSCs are constrained by light-induced halide segregation and non-radiative recombination losses. In this study, this work presents an approach of utilizing 2-methylpiperazinium bromide (2-MePBr) via interfacial engineering to realize high-efficiency WBG (1.77 eV) PSCs. The C & horbar;NH & horbar;C functional group in 2-MePBr, serving as an electron donor, can interact with under-coordinated lead defects at the perovskite surface. Consequently, the treatment with 2-MePBr mitigates interfacial non-radiative recombination, enhances charge transport, inhibits ion migration, and thus delivers an improved power conversion efficiency (PCE) of 19.30% with a VOC of 1.29 V, and a fill factor of 83.08%. Notably, the WBG PSCs manifest enhanced stability, preserving 80% of the initial PCE after 337 h of continuous operation under 1 sun illumination at the maximum power point. Furthermore, the all-perovskite TSCs based on this WBG subcell achieve a PCE of 27.47%, showing its promising application in perovskite-based tandem solar cells. The 2-methylpiperazinium bromide (2-MePBr) is employed to treat the surface of wide-bandgap (1.77 eV) perovskites to inhibit the ion migration and passivate defects. The 2-MePBr treatment has resulted in an improved power conversion efficiency of 19.30% with a VOC of 1.29 V and a remarkable fill factor of 83.08%, as well as enhanced stability. image

The efficiency of all‐perovskite tandem solar cells has recently surpassed that of single‐junction perovskite solar cells, showing great potential as a future photovoltaic technology due to its low manufacturing cost and high power conversion efficiency potential, yet the size of these cells is still at the laboratory level. It is highly required to develop scalable preparation methods to fabricate large‐area all‐perovskite tandem solar modules for commercial applications. Herein, the key challenges encountered in the laboratory of all‐perovskite tandem solar cells and the existing solutions are summarized and some views on the preparation of large areas and modules are given.

All-perovskite tandem solar cells (TSCs) have exhibited higher efficiencies than single-junction perovskite solar cells (PSCs) but still suffer from the unsatisfactory performance of low-bandgap (LBG) tin-lead (Sn-Pb) subcells. The inherent properties of PEDOT:PSS are crucial to high-performance Sn-Pb perovskite films and devices; however, the underlying mechanism has not been fully explored and revealed. Here, we report a facile oxalic acid treatment of PEDOT:PSS (OA-PEDOT:PSS) to precisely regulate its work function and surface morphology. OA-PEDOT:PSS shows a larger work function and an ordered reorientation and fiber-shaped film morphology with efficient hole transport pathways, leading to the formation of more ideal hole-selective contact with Sn-Pb perovskite for suppressing interfacial nonradiative recombination losses. Moreover, OA-PEDOT:PSS induces (100) preferred orientation growth of perovskite for higher-quality Sn-Pb films. Last, the OA-PEDOT:PSS–tailored LBG PSC yields an impressive efficiency of up to 22.56% (certified 21.88%), enabling 27.81% efficient all-perovskite TSC with enhanced operational stability.

Wide-bandgap (> 1.7 eV) perovskites suffer from severe light-induced phase segregation due to high bromine content, causing irreversible damage to device stability. However, the strategies of suppressing photoinduced phase segregation and related mechanisms have not been fully disclosed. Here, we report a new passivation agent 4-aminotetrahydrothiopyran hydrochloride (4-ATpHCl) with multifunctional groups for the interface treatment of a 1.77-eV wide-bandgap perovskite film. 4-ATpH+ impeded halogen ion migration by anchoring on the perovskite surface, leading to the inhibition of phase segregation and thus the passivation of defects, which is ascribed to the interaction of 4-ATpH+ with perovskite and the formation of low-dimensional perovskites. Finally, the champion device achieved an efficiency of 19.32% with an open-circuit voltage (VOC) of 1.314 V and a fill factor of 83.32%. Moreover, 4-ATpHCl modified device exhibited significant improved stability as compared with control one. The target device maintained 80% of its initial efficiency after 519 h of maximum power output (MPP) tracking under 1 sun illumination, however, the control device showed a rapid decrease in efficiency after 267 h. Finally, an efficiency of 27.38% of 4-terminal all-perovskite tandem solar cells was achieved by mechanically stacking this wide-bandgap top subcell with a 1.25-eV low-bandgap perovskite bottom subcell.

A DMPU custom-tailored solvent system effectively improved the film quality of perovskites, achieving one of the highest VOC of 1.256 V for 1.65 eV wide-bandgap PSCs.

All-perovskite tandem solar cells (TSCs) hold great promise in terms of ultrahigh efficiency, low manufacturing cost, and flexibility, stepping forward to the next-generation photovoltaics. However, their further development is hampered by the relatively low performance of low-bandgap (LBG) tin (Sn)-lead (Pb) perovskite solar cells (PSCs). Improving the carrier management, including suppressing trap-assisted non-radiative recombination and promoting carrier transfer, is of great significance to enhance the performance of Sn-Pb PSCs. Herein, a carrier management strategy is reported for using cysteine hydrochloride (CysHCl) simultaneously as a bulky passivator and a surface anchoring agent for Sn-Pb perovskite. CysHCl processing effectively reduces trap density and suppresses non-radiative recombination, enabling the growth of high-quality Sn-Pb perovskite with greatly improved carrier diffusion length of >8 µm. Furthermore, the electron transfer at the perovskite/C60 interface is accelerated due to the formation of surface dipoles and favorable energy band bending. As a result, these advances enable the demonstration of champion efficiency of 22.15% for CysHCl-processed LBG Sn-Pb PSCs with remarkable enhancement in both open-circuit voltage and fill factor. When paired with a wide-bandgap (WBG) perovskite subcell, a certified 25.7%-efficient all-perovskite monolithic tandem device is further demonstrated.

The efficiency of all-perovskite tandem solar cells has surpassed that of single-junction perovskite solar cells, yet they still suffer from interfacial non-radiative recombination losses. Charge-selective materials that can reduce such losses as well as fabrication cost “applicable” to both subcells should be developed. Here we design a donor–acceptor-type molecule, MPA2FPh-BT-BA (2F), as a hole-selective contact suitable to both wide-bandgap (WBG) and low-bandgap (LBG) subcells for high-performance all-perovskite tandem solar cells. In the WBG cell, 2F enables efficient hole extraction and minimizes interfacial non-radiative recombination losses by passivating interfacial defects. In the LBG cell, 2F suppresses interfacial losses, regulates the crystal growth and enhances Sn–Pb perovskite film quality. As a result, 2F-treated WBG and LBG devices yield efficiencies of 19.33% (certified 19.09%) and 23.24%, respectively, enabling monolithic all-perovskite tandem solar cells with an efficiency of 27.22% (certified 26.3%) and improved operational stability.

A thiazolidine-based interfacial modification strategy is developed for wide-bandgap perovskite solar cells to promote the efficiency to 20.02% with a reduced V OC deficit of 0.51 V, along with good near-infrared transmittance.

Perovskite solar cells (PSCs) and organic solar cells (OSCs) face device efficiency losses and instability challenges with existing hole transport materials (HTMs). The development of new universal HTMs is in great demand to promote their practical applications. Herein, a versatile self‐assembled molecule (SAM) based HTM is designed for record‐high efficiency wide‐bandgap (WBG, E g >1.75 eV) PSCs, all‐perovskite tandem solar cells (TSCs) and OSCs. The SAM exhibits high transmission and a lower‐lying energy level, enabling enhanced interfacial charge transfer and suppressed non‐radiative recombination losses. SAM based WBG PSCs deliver a maximum power conversion efficiency (PCE) of 18.63% with over 90% efficiency retention after 250 h continuous work. By stacking the optimal WBG PSC and a narrow‐bandgap PSC bottom cell, the 4‐terminal all‐perovskite TSC achieves a remarkable 26.24% PCE. More importantly, this SAM based HTM exhibits impressive generality in bulk heterojunction OSCs rivalling PEDOT:PSS, with an impressive PCE of 18.84% obtained for PM6:BTP‐eC9 based devices. When scaling up the PM6:BTP‐eC9 device to 0.5 cm 2 in area (0.71 cm × 0.71 cm), the SAM based OSCs afford a highest PCE of 16.33%. This work provides a perspective for the design of universal SAM based charge transport materials targeting PSCs and OSCs for facile large‐area fabrication.