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Metal halide perovskite photodiodes have garnered extensive attention owing to their favorable optoelectronic properties, rendering them attractive for visible, near‐infrared, and X‐ray sensors. However, their predominant reliance on solution‐processing deposition techniques poses challenges for seamless integration into existing industrial processes. In this study, this limitation is addressed by developing fully vacuum‐processed perovskite photodiodes with varying hole transport layers (HTL). These findings underscore the critical role of HTL selection in influencing the dark and noise current characteristics of the diodes. With an optimized HTL, photodiodes are obtained with low noise current (≈3 10−14 A Hz−1/2) and high specific detectivity (≈1012 Jones at 710 nm at −0.5 V). The photodiodes are also tested as X‐ray detectors and are found to be stable under X‐ray radiation, with state‐of‐the‐art sensitivity of 33 ± 4 µC Gy−1 cm−2 and a low limit of detection of 2.0 ± 1.6 µG s−1. These insights contribute to the development of perovskite photodiodes with improved performance and broader industrial applicability. [ABSTRACT FROM AUTHOR]

Trap states in organic semiconductors are notoriously detrimental to the performance of organic electronics. However, the origin and energetics of trap states remain largely elusive and under debate, especially for bulk‐heterojunction (BHJ) photodiodes consisting of electron donor and acceptor materials. Combining three sensitive techniques now enables locating the origin and energy of trap states in six state‐of‐the‐art polymer – non‐fullerene acceptor organic photodiodes (OPDs) with noise‐based specific detectivities exceeding 1013 Jones. Analyzing the temperature dependence of the reverse‐bias dark current density (Jd) identifies intra‐gap states in the polymers, lying 0.3−0.4 eV above the energy of the highest occupied molecular orbital, as being responsible for Jd. Sub‐bandgap external quantum efficiency spectra of donor‐only and acceptor‐only diodes confirm that intra‐gap states are much more abundant in the polymers. Likewise, responsivity measurements at ultra‐low light intensities (10−7 mW cm−2) show trap‐mediated charge recombination in BHJ and polymer‐only diodes, but not in acceptor‐only devices. The results imply that to further improve the specific detectivity of near‐infrared OPDs, the intra‐gap state energy, and density need to be reduced. [ABSTRACT FROM AUTHOR]

The performance of organic photodetectors is steadily improving, and the specific detectivity, as a key figure of merit, has reached values of 1012–1013 Jones, i.e., comparable to that of silicon diodes but still considerably lower than the intrinsic limit. As with other semiconductor devices, the electrical performance of state‐of‐the art organic photodiodes (OPDs) is presently determined to a high degree by the presence of chemical impurities or structural defects which create carrier trapping states within the bandgap of organic active layer. This review aims to provide a comprehensive and timely account of trap‐assisted charge generation and recombination in OPDs, with emphasis on the impact of these phenomena on photodetector performance parameters such as, noise and dark current density, responsivity, response speed, and ultimately, specific detectivity. [ABSTRACT FROM AUTHOR]

Metal halide perovskite photodiodes (PPDs) offer high responsivity and broad spectral sensitivity, making them attractive for low-cost visible and near-infrared sensing. A significant challenge in achieving high detectivity in PPDs is lowering the dark current density (JD) and noise current (in). This is commonly accomplished using charge-blocking layers to reduce charge injection. By analyzing the temperature dependence of JD for lead-tin based PPDs with different bandgaps and electron-blocking layers (EBL), we demonstrate that while EBLs eliminate electron injection, they facilitate undesired thermal charge generation at the EBL-perovskite interface. The interfacial energy offset between the EBL and the perovskite determines the magnitude and activation energy of JD. By increasing this offset we realized a PPD with ultralow JD and in of 5 × 10−8 mA cm−2 and 2 × 10−14 A Hz−1/2, respectively, and wavelength sensitivity up to 1050 nm, establishing a new design principle to maximize detectivity in perovskite photodiodes. In lead‐tin halide perovskite photodiodes, the interfacial energy offset at the charge transport layer controls the dark current. In this work, by increasing this offset, the authors demonstrates a photodiode with ultralow dark and noise currents and high near‐infrared sensitivity. [ABSTRACT FROM AUTHOR]

In recent years there has been an increasing interest to integrate optical sensing in mobile displays, for instance, for biometric fingerprint scanning functionality. There are several routes to incorporate optical fingerprint functionality within the full display area, each with their own benefits and challenges. Here we investigate the different integration routes using large‐area, ultra‐thin imagers based on organic photodiodes. [ABSTRACT FROM AUTHOR]

In recent years there is an increasing interest to integrate optical sensing in mobile displays, for instance, for biometric fingerprint scanning functionality. There are several routes to incorporate optical fingerprint functionality within the full display area, each with their own benefits and challenges. Here we investigate the different integration routes using large‐area, ultrathin imagers based on organic photodiodes. [ABSTRACT FROM AUTHOR]

Reflectance oximeters based on organic photodiode (OPD) arrays offer the potential to map blood pulsation and oxygenation via photoplethysmography (PPG) over a large area and beyond the traditional sensing locations. Here, an organic reflectance PPG array based on 16 × 16 OPD pixels is developed. The individual pixels exhibit near‐infrared sensitivity up to ≈950 nm and low dark current density in the order of 10−6 mA cm−2. This results in high‐quality PPG signals. Analysis of the full PPG waveform yields insight on the artery stiffness and the quality of blood circulation, demonstrating the potential of these arrays beyond pulse oximetry and heart‐rate calculation. [ABSTRACT FROM AUTHOR]

Using flat‐panel compatible processes we realized 6x8 cm, 200‐ppi active‐matrix imagers with solution‐processed, ultrathin organic photodiodes and demonstrate its performance in a biometric palmprint detector. [ABSTRACT FROM AUTHOR]

The dynamic response of an organic bulk heterojunction photodiode to small changes in applied bias or light intensity is investigated as function of the intensity of a constant background illumination by means of photoimpedance and transient photocurrent measurements. For bias voltages close to the open circuit voltage we find that the response timescale with the square root of the light intensity. The results can be quantitatively explained in terms of a space charge limitation on the photocurrent as predicted by Goodman and Rose ( J. Appl. Phys . 42 , 2823 (1971)). The relaxation time of the diode at open circuit corresponds to the lifetime of the slowest charge carrier in the diode. This relaxation time is determined by the dielectric constant and the smallest of the two carrier mobilities in the bulk heterojunction. This illustrates the importance of balanced carrier mobilities for obtaining diodes with fast response time at low bias for e.g. imaging arrays. [ABSTRACT FROM AUTHOR]

We made and characterized an X-ray detector on a 25- \mu \textm -thick plastic substrate that is capable of medical-grade performance. As an indirect conversion flat panel detector, it combined a standard scintillator with an organic photodetector (OPD) layer and oxide thin-film transistor backplane. Using solution-processed organic bulk heterojunction photodiode rather than the usual amorphous silicon, process temperature is reduced to be compatible with plastic film substrates, and a number of costly lithography steps are eliminated, opening the door to lower production costs. With dark currents as low as 1 pA/mm ^2 and sensitivity of 0.2 A/W the OPD also meets functional requirements: the proof-of-concept detector delivers high-resolution, dynamic images at 10 frames/s, and 200 pixels/in using X-ray doses as low as $3~\mu $ Gy/frame. [ABSTRACT FROM AUTHOR]

We report on the fabrication of imagers based on organic semiconductors both in the photodiode layer and in the readout backplane. The photodiode is based on evaporated ultrathin (<;100 nm) stack of SubPc/C60, sensitive in the wavelength range between 300 and 650 nm. The readout circuit is a switch matrix fabricated with a solution processed semiconductor (XPRD30B01) and two solution processed, crosslinkable dielectrics (XDRD30B01). The readout TFTs (140/5-μm channel width/length, respectively) have leakage current lower than 1 pA with the ON-current higher than 0.1 μA. The 32 × 32 pixel imagers with pixel pitch down to 200 μm are demonstrated with mean dark signal of a few μA/cm2 and linear photoresponse up to the incident power of 100 μW. These results show feasibility of fabricating readout circuits with TFTs based on crosslinkable dielectrics. This enables reduction of two patterning steps (opening of the gate dielectric and of the encapsulation layer) to just photolithography, leading to simplification of the backplane manufacturing process. [ABSTRACT FROM PUBLISHER]

Highlights: [•] A very thin and light-weight X-ray imager is made on plastic film. [•] All layers with the exception of the electrodes are solution processed. [•] The photo-sensitive layer is continuous, simplifying the manufacturing process. [•] Images are recorded at X-ray doses sufficiently low for medical applications. [ABSTRACT FROM AUTHOR]

Minimizing the reverse bias dark current while retaining external quantum efficiency is crucial if the light detection sensitivity of organic photodiodes (OPDs) is to compete with inorganic photodetectors. However, a quantitative relationship between the magnitude of the dark current density under reverse bias (Jd) and the properties of the bulk heterojunction (BHJ) active layer has so far not been established. Here, a systematic analysis of Jd in state‐of‐the‐art BHJ OPDs using five polymers with a range of energy levels and charge transport characteristics is presented. The magnitude and activation energy of Jd are explained using a model that assumes charge injection from the metal contacts into an energetically disordered semiconductor. By relating Jd to material parameters, insights into the origin of Jd are obtained that enable the future selection of successful OPD materials. [ABSTRACT FROM AUTHOR]