area >10 cm 2 . They mostly focus on efficient approaches for qualitative coating/ printing of perovskite over large areas like blade coating, pneumatic squeezing, slot die, CVD, co-evaporation, spin coating, etc. [2] The certified mini-module results recorded in the NREL chart encourages the PV community to further enhance their efficiency and stability with vast options of large area processability. [1b] As of today, most of the reported high-efficiency PSM employs thick and opaque perovskite with Au top contact.However, to extend PSM's application for BIPV especially for power generating windows, one needs to have visibly semitransparent (ST) devices. This demands a collective average visible transparency (AVT) of >20% for the full device stack. [3] Some reports to fabricate ST PSC focus mainly on different strategies of ST perovskite film such as ultra-thin film deposition, micro structuring including printing, dewetting, selfassembly, etc. Amongst these, ultrathin films (≈250 nm) show comparatively higher efficiencies and controlled procedures. [4] Their final PCE (Power Conversion Efficiency) is reported with Au/Ag metal (opaque) contact which does not give a clear picture of full ST PSC performance. Other reports of ST PSC focus only on replacing the top metal contact Au/Ag with transparent conductors such as ITO, MoO x , Ag nanowires, graphene, DMD (dielectric-metal-dielectric) stack wherein the perovskite is not semitransparent (AVT < 20%). [5] Often the term "semitransparent" in the title of these articles is misleading as different authors refer to different optical regions (visible or IR) of interest and sometimes the transparency is calculated without the top electrode. This raises a concern because the interaction/adhesion behavior of ST perovskite with the transparent top contacts is different as compared to their opaque counterparts, and one cannot simply infer that similar efficiency will be achieved when replacing the metal electrode with a transparent conductor. While highlighting this ambiguity and the lack of sufficient work in the semitransparent large area PSM, in this work, we address three major problems encountered in ST solar cells by 1) improving the quality of ultrathin perovskite, 2) designing a high-quality transparent contact, and 3) compensating the reduced photon absorption by additional photon harvesting material.Starting with the first problem, ultra-thin perovskite underperforms as compared to the standard thickness not only Significant advancements in the perovskite solar cells/modules (PSCs/PSMs) toward better operational stability and large area scalability have recently been reported. However, semitransparent (ST), high efficiency, and large area PSMs are still not well explored and require attention to realize their application in building-integrated photovoltaics (BIPV). This work employs multiple synergistic strategies to improve the quality and stability of the ST perovskite film while ensuring high transparency. Europium ions, doped in the perovskite, are found to...

Inorganic hole-transport layers (HTLs) are widely investigated in perovskite solar cells (PSCs) due to their superior stability compared to the organic HTLs. However, in p-i-n architecture when these inorganic HTLs are deposited before the perovskite, it forms a suboptimal interface quality for the crystallization of perovskite, which reduces device stability, causes recombination, and limits the power conversion efficiency of the device. The incorporation of an appropriate functional group such as sulfurterminated surface on the HTL can enhance the interface quality due to its interaction with perovskite during the crystallization process. In this work, a bifunctional Al-doped CuS film is wet-deposited as HTL in p-i-n architecture PSC, which besides acting as an HTL also improves the crystallization of perovskite at the interface. Urbach energy and light intensity versus open-circuit voltage characterization suggest the formation of a better-quality interface in the sulfide HTL-perovskite heterojunction. The degradation behavior of the sulfide-HTL-based perovskite devices is studied, where it can be observed that after 2 weeks of storage in a controlled environment, the devices retain close to 95% of their initial efficiency.

There is broad interest in developing photonically active substrates from naturally abundant, minimally processed materials that can help to overcome the environmental challenges of synthetic plastic substrates while also gaining inspiration from biological design principles. To date, most efforts have focused on rationally engineering the micro‐ and nanoscale structural properties of cellulose‐based materials by tuning fibril and fiber dimensions and packing along with chemical modifications, while there is largely untapped potential to design photonically active substrates from other classes of natural materials with distinct morphological features. Herein, the fabrication of a flexible pollen‐derived substrate is reported, which exhibits high transparency (>92%) and high haze (>84%) on account of the micro‐ and nanostructure properties of constituent pollen particles that are readily obtained from nature and require minimal extraction or processing to form the paper‐like substrate based on colloidal self‐assembly. Experiments and simulations confirm that the optical properties of the pollen substrate are tunable and arise from light–matter interactions with the spiky surface of pollen particles. In a proof‐of‐concept example, the pollen substrate is incorporated into a functional perovskite solar cell while the tunable optical properties of the intrinsically micro‐/nanostructured pollen substrate can be useful for a wide range of optoelectronic applications.