Novel, low‐voltage, high‐detectivity, solution‐processed, flexible near‐infrared (NIR) photodetectors for optoelectronic applications are realized and their optoelectronic properties are investigated for the first time. This is achieved by synthesizing Ag2Se nanoparticles (NPs) in aqueous solutions, and depositing highly crystalline Ag2Se thin films at 150 °C with redistributed Ag2Se NPs in aqueous inks. The high conductivity and low trap concentration of the 150 °C annealed Ag2Se films result from the Ag formed inside the films and the improved film quality, respectively. These factors are both critical for the realization of high‐performance flexible photodetectors. The fabricated device exhibits a high detectivity of 7.14 × 109 Jones (above 1 × 109) at room temperature, delivering low power consumption. This detectivity is superior to those of reported low band‐gap semiconductor systems, although the device has undergone 0.38% compressive and tensile strains. Moreover, the performance of the device is better than that of MoS2‐based phototransistors, black arsenic phosphorus field‐effect transistors, or commercial thermistor bolometers at room temperature (D* ≈ 108 Jones), and is exposed to mid‐infrared light.

No abstract

Solvent engineering by Lewis‐base solvent and anti‐solvent is well known for forming uniform and stable perovskite thin films. The perovskite phase crystallizes from an intermediate Lewis‐adduct upon annealing‐induced crystallization. Herein, it is explored the effects of trimethyl phosphate (TMP), as a novel aprotic Lewis‐base solvent with a low donor number for the perovskite film formation and photovoltaic characteristics of perovskite solar cells (PSCs). As compared to dimethylsulfoxide (DMSO) or dimethylformamide (DMF), the usage of TMP directly crystallizes the perovskite phase, i.e., reduces the intermediate phase to a negligible degree, right after the spin‐coating, owing to the high miscibility of TMP with the anti‐solvent and weak bonding in the Lewis adduct. Interestingly, the PSCs based on methylammonium lead iodide (MAPbI3) derived from TMP/DMF‐mixed solvent exhibit a higher average power conversion efficiency of 19.68% (the best: 20.02%) with a smaller hysteresis in the current‐voltage curve, compared to the PSCs that are fabricated using DMSO/DMF‐mixed (19.14%) or DMF‐only (18.55%) solvents. The superior photovoltaic properties are attributed to the lower defect density of the TMP/DMF‐derived perovskite film. The results indicate that a high‐performance PSC can be achieved by combining a weak Lewis base with a well‐established solvent engineering process.

No abstract

No abstract