Xin Zhang

Thin film photodiodes (TFPD) can supplement complementary metal-oxide-semiconductor (CMOS) image sensor vision by their exotic optoelectronic properties assisted by their monolithic processability. Halide perovskites are known to show outstanding optoelectronic properties, such as large absorption coefficient, long carrier diffusion lengths, and high carrier mobility, leading to high external quantum efficiency (EQE) and fast charge transport in photodiodes (PDs), especially compared with other thin-film photodiode candidates. In this paper, high-resolution two-dimensional (2D) and three-dimensional (3D) imaging capabilities are demonstrated using perovskite photodetection material with a silicon (Si) read-out integrated circuit (ROIC). The integration of this perovskite photodiode (PePD) on the Si ROIC provides fine resolution for 2D imaging. The fast carrier transport properties of the PePD enable depth sensing of objects using the same sensor. 3D imaging is demonstrated using the proposed top-electrode controlled indirect time-of-flight (iToF) operation supported by the fast PD switching through the top common electrode of the TFPD image sensor pixel. It is expected that the PePDs on Si ROIC could mark a significant milestone for the TFPD imaging platform with their outstanding optoelectronic performance in combination with the CMOS image sensor technology, not only for conventional 2D imaging but also by enabling extensions toward 3D sensing, promising applications in automotive, augmented reality (AR), and virtual reality (VR).

Sputtered nickel oxide (NiO_x) has become one of the most promising inorganic hole transport layers for p–i–n perovskite solar cells (PSCs) due to its appealing features such as its robust nature, low material cost, and easy integration to tandem structures and large‐area applications. However, the main drawback with NiO_x‐based PSCs is typically low open‐circuit voltage (V_OC) due to the inferior energy‐level alignment, low charge mobility, and high recombination at the interface. Herein, two types of phosphonic acid self‐assembled monolayers (SAMs) deposited by blade coating as an interfacial layer to modulate the sputtered NiO_x/perovskite interface properties are used. While sputtered NiO_x serves as a conformally coated hole selective layer, the ultrathin SAM interlayer facilitates the hole extraction and minimizes the energy loss at the interface. Co‐ordinately introduced stabilizing additive, namely octadecyl 3‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl)propionate (I‐76), further improves the device performance of NiO_x/SAM‐based PSCs, resulting in V_OC of 1.14 V and a power conversion efficiency of 21.8%. By applying these strategies for perovskite module upscaling, aperture area module efficiencies of 19.7%, 17.5%, and 15.5% for perovskite minimodules of 4, 16, and 100 cm² are demonstrated, corresponding to active area module efficiencies of 20.4%, 18.0%, and 16.4%, respectively.

Optoelectronic synaptic transistors are attractive for applications in next-generation brain-like computation systems, especially for their visible-light operation and in-sensor computing capabilities. However, from a material perspective, it is difficult to build a device that meets expectations in terms of both its functions and power consumption, prompting the call for greater innovation in materials and device construction. In this study, we innovatively combined a novel perovskite carrier supply layer with an Al/MoO₃ interface carrier regulatory layer to fabricate optoelectronic synaptic devices, namely Al/MoO₃/CsFAMA/ITO transistors. The device could mimic a variety of biological synaptic functions and required ultralow-power consumption during operation with an ultrafast speed of >0.1 μs under an optical stimulus of about 3 fJ, which is equivalent to biological synapses. Moreover, Pavlovian conditioning and visual perception tasks could be implemented using the spike-number-dependent plasticity (SNDP) and spike-rate-dependent plasticity (SRDP). This study suggests that the proposed CsFAMA synapse with an Al/MoO₃ interface has the potential for ultralow-power neuromorphic information processing.

The metal halide perovskite absorbers are prone to surface defects, which severely limit the power conversion efficiencies (PCEs) and the operational stability of the perovskite solar cells (PSCs). Herein, trace amounts of bithiophene propylammonium iodide (bi-TPAI) are applied to modulate the surface properties of the gas-quenched perovskite. It is found that the bi-TPAI surface treatment has negligible impact on the perovskite morphology, but it can induce a defect passivation effect and facilitate the charge carrier extraction, contributing to the gain in the open-circuit voltage (V_oc) and fill factor. As a result, the PCE of the gas-quenched sputtered NiO_x-based inverted PSCs is enhanced from the initial 20.0% to 22.0%. Most importantly, the bi-TPAI treatment can largely alleviate or even eliminate the burn-in process during the maximum power point tracking measurement, improving the operational stability of the devices.

Preferred crystalline orientation at the surface of quasi-2D organic-inorganic halide perovskites is crucial to promote vertical carrier transport and interface carrier extraction, which further contribute to device efficiency and stability in photovoltaic applications. However, loose unoriented and defective surfaces are inevitably formed in the crystallization process, especially with the introduction of bulky organic cations into the quasi-2D perovskites. Here, a facile and effective surface polishing method using a natural-friendly green solvent, 2,2,2-trifluoroethanol, is proposed to reconstruct the surface. After solvent polishing, the randomly oriented phases containing trap sites on the surface are successfully removed, and the compact vertical-oriented phases underneath are revealed with less defectiveness and better smoothness, which greatly facilitates carrier transport and interfacial charge extraction. Consequently, the green solvent polished devices show a boosting efficiency of 18.38% with a high open-circuit voltage of 1.21 V. The devices also show improved storage and operational stability.

Volatile A-cation halide (AX) additives such as formamidinium chloride and methylammonium chloride have been widely employed for high-efficiency perovskite solar cells (PSCs). However, it remains unstudied how they influence the perovskite film stoichiometry and the solar cell performance and operational stability. Hereby, our work shows that over annealing of formamidinium chloride-containing perovskite films leads to a Pb-rich surface, resulting in a high initial efficiency, which however decays during maximum power point tracking (MPPT). On the contrary, perovskite films obtained by a shorter annealing time at the same temperature provide good stability during MPPT but a lower initial efficiency. Thus, we deduce that an optimal annealing is vital for both high efficiency and operational stability, which is then confirmed in the case where methylammonium chloride additive is used. With optimized perovskite annealing conditions, we demonstrate efficient and stable p-i-n PSCs that show a best power conversion efficiency of 20.7% and remain 90% of the initial performance after a 200 h MPPT at 60 °C under simulated 1 sun illumination with high UV content. Our work presents a comprehensive understanding on how volatile AX impacts perovskite film stoichiometry and its correlation to the device performance and operational stability, providing a new guideline for fabricating high-efficiency and operationally stable PSCs.