The construction of high-speed electronic devices that can be integrated using a single two-dimensional (2D) semiconductor with high performance remains challenging due to the absence of locally selective doping methods. In this study, we have demonstrated that the selective opposite polarities (p-type or n-type) from an intrinsic 2H-MoTe2 field-effect transistor (FET) can be configured through carrier type band modulation in molybdenum ditelluride (MoTe2) caused by the charge storage interface in MoTe2/BN vdW heterostructures upon UV illumination with electrostatic gate bias. With this approach, we demonstrate a lateral p-i-n homojunction diode (p-MoTe2/intrinsic-MoTe2/n-MoTe2) using a single two-dimensional semiconductor (2H-MoTe2) where an intrinsic FET (i-type region) is sandwiched between p- and n-type FETs. Electrical performance of such a p-i-n diode demonstrates an ideal rectifying behavior with a rectification ratio (I f/I r) of up to ∼1.4 × 106 at zero gate bias with an ideal value of the ideality factor of nearly ∼1. To support optoelectrical doping, Kelvin probe force microscopy (KPFM) measurements are performed where p- and n-type MoTe2 channels show work function values of ∼5.0 and ∼ 4.55 eV, respectively, with a built-in potential of ∼450 mV. In the photovoltaic mode, the p-i-n diode shows excellent photodetection properties under an illumination of 600 nm, a maximum value of responsivity of 1.10 A/W, and a specific detectivity value of 3.0 × 1012 Jones. The device shows ultrafast photoresponses, where the response speed (τr/τf) is estimated to be 10/20 ns. The proposed research offers an opportunity for creating stable p-i-n homojunction diodes for high-speed electronics with low power consumption using 2D materials.

Here, van der Waals multi‐heterojunctions (PN, NP, PIN, and NPN) are fabricated by stacking of MoTe2, hexagonal boron nitride (h‐BN), and MoSe2 nanoflakes using a mechanical‐exfoliation technique where the dynamic rectification is examined. Low‐resistance metal contacts Al/Au and Pt/Au are applied to MoSe2 and MoTe2, respectively, and gate‐dependent rectifying behavior is achieved, with a rectification ratio of up to 105 in PN devices. It is found that the performance of the device is enhanced by placing an interfacial layer h‐BN between two opposite layers of 2D materials where the rectification ratio is found to be >106 with the ideality factor ≈1.3 in the PIN devices. Also, using the conventional Richardson's plot, the barrier heights of PN and PIN diodes are calculated to be 260 and 490 meV at zero gate bias, respectively. As well, the devices exhibit good performance with a built‐in electric field observed in both PN and PIN diodes, which gives rise to an open‐circuit voltage (Voc) and short‐circuit current (Isc) under zero external bias. Remarkably, it is found that the performance of the devices also gets better by forming double heterojunction (NPN) layer than PN or NP layers. The device is also tested for a rectification application, and it successfully rectifies an input alternating‐current signal. These findings are important for the development of nano‐ and optoelectronics devices.

Graphene (Gr) has shown a significant role in photovoltaic applications due to its exclusive properties. In this study, we established a facile approach to fabricate p-Gr/HfO2/n-silicon, a metal–insulator–semiconductor (MIS) Schottky junction solar cell. Nevertheless, the poor work function of Gr and high-density defect states at the Gr/Si interface obstruct the efficiency of solar cells. To avoid this problem, the optimal thickness of the interfacial layer (HfO2) is employed, which circumvents the recombination process at the Gr/Si interface. Additionally, to boost the Schottky barrier height and Gr’s work function, a combination of p-type co-doping of organic molecule 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) and Br is studied. Therefore, a higher work function aims to encourage the built-in potential, which ultimately improves the open-circuit voltage and current density and deteriorates the series resistance of solar cells. Hence, a unique combination of dopants resulted in improved efficiency of up to 12.31%. Moreover, devices with double layer (MoO3/HfO2) passivation have been enabled to provide outstanding stability for over 180 days. The combined effect of p-type co-doping and double layer passivation developed a solar cell having a significant efficiency of 14.01%. Thus, this work intends to show a promising, high-performance and stable MIS Schottky junction solar cell for massive commercialization of photovoltaic devices.

In this study, P3HT:PC 61 BM was utilized to fabricate flexible organic solar cells (OSCs) on the polyethylene terephthalate substrates under an ambient atmosphere. An efficient electron transport layer (ETL) was employed to achieve a better device performance. The ETL was fabricated by making a nanocomposite from zinc oxide (ZnO) and polyethyleneimine ethoxylated (PEIE). The PEIE doping causes the reduction of work function of ZnO as well as passivates the interface, which ultimately improved the performance of the solar cell. The ZnO device's performance was 0.80%, which was effectively enhanced to 0.95% after the PEIE doping with an increase in the FF and J sc . The ZnO's reduced work function due to PEIE is responsible for easy charge conveyance from the photoactive layer to the cathode, which enhances the FF and J sc values. Besides, the flexible OSCs with the ZnO:PEIE ETL demonstrate more improvements in the mechanical property than with ZnO. The device with the ZnO:PEIE ETL sustained around 80% of its original power conversion efficiency (PCE) after 800 bending cycles. Thus, this study can contribute to the future large-scale manufacturing of flexible OSCs by using the ZnO:PEIE ETL.

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