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Lead (Pb)–Tin (Sn) mixed perovskites suffer from large open-circuit voltage (Voc) loss due to the rapid crystallization of perovskite films, creating Sn and Pb vacancies. Such vacancies act as defe...

III-Nitride light emitting diodes (LEDs) are widely used in a range of high efficiency lighting and display applications, which has enabled significant energy savings in the last decade. Despite the wide application of GaN LEDs, transport mechanisms across InGaN/GaN heterostructures in these devices are not well explained. Fixed polarization sheet charges at InGaN/GaN interfaces lead to large interface dipole charges, which create large potential barriers to overcome. One-dimensional models for transport across such heterostructures predict turn-on voltages that are significantly higher than that found in real devices. As a result, conventional models for transport cannot predict the performance of new designs such as for longer wavelength LEDs or for multi-quantum well LEDs. In this work, we show that incorporating low and high indium compositions within quantum wells at the submicrometer scale can provide an accurate prediction of the characteristics of GaN/InGaN light emitting diodes.

Ultra-violet (UV) light emitting diodes operating at 339 nm using transparent interband tunnel junctions are reported. Tunneling-based ultraviolet light emitting diodes were grown by plasma-assisted molecular beam epitaxy on 30% Al-content AlGaN layers. A low tunnel junction voltage drop is obtained through the use of compositionally graded n and p-type layers in the tunnel junction, which enhance hole density and tunneling rates. The transparent tunnel junction-based UV LED reported here show a low voltage drop of 5.55 V at 20 A/cm2 and an on-wafer external quantum efficiency of 1.02% at 80 A/cm2.

Solid-state lithium batteries are generally considered as the next-generation battery technology that benefits from inherent nonflammable solid electrolytes and safe harnessing of high-capacity lithium metal. Among various solid-electrolyte candidates, cubic garnet-type Li7La3Zr2O12 ceramics hold superiority due to their high ionic conductivity (10–3 to 10–4 S cm−1) and good chemical stability against lithium metal. However, practical deployment of solid-state batteries based on such garnet-type materials has been constrained by poor interfacing between lithium and garnet that displays high impedance and uneven current distribution. Herein, we propose a facile and effective strategy to significantly reduce this interfacial mismatch by modifying the surface of such garnet-type solid electrolyte with a thin layer of silicon nitride (Si3N4). This interfacial layer ensures an intimate contact with lithium due to its lithiophilic nature and formation of an intermediate lithium–metal alloy. The interfacial resistance experiences an exponential drop from 1197 to 84.5 Ω cm2. Lithium symmetrical cells with Si3N4-modified garnet exhibited low overpotential and long-term stable plating/stripping cycles at room temperature compared to bare garnet. Furthermore, a hybrid solid-state battery with Si3N4-modified garnet sandwiched between lithium metal anode and LiFePO4 cathode was demonstrated to operate with high cycling efficiency, excellent rate capability, and good electrochemical stability. This work represents a significant advancement toward use of garnet solid electrolytes in lithium metal batteries for the next-generation energy storage devices.

We demonstrate p-down green emitting LEDs with low turn-on voltage enabled by efficient tunnel junctions. Due to the polarization field alignment in the (In,Ga)N/GaN interface with the p-down orientation, the electrostatic depletion barrier for electron and hole injection is reduced when compared with the conventional p-up LEDs. A single (In,Ga)N/GaN heterostructure quantum well active region with a GaN homojunction tunnel junction exhibited very low forward operating voltage of 2.42 V at 20 A/cm2 with a peak electroluminescence emission wavelength of 520 nm for current densities above 100 A/cm2. The bottom tunnel junction with minimal voltage drop enabled excellent hole injection into the bottom p-GaN layer.

Perovskites have been unprecedented with a relatively sharp rise in power conversion efficiency in the last decade. However, the polycrystalline nature of the perovskite film makes it susceptible to surface and grain boundary defects, which significantly impedes its potential performance. Passivation of these defects has been an effective approach to further improve the photovoltaic performance of the perovskite solar cells. Here, we report the use of a novel hydrazine-based aromatic iodide salt or phenyl hydrazinium iodide (PHI) for secondary post treatment to passivate surface and grain boundary defects in triple cation mixed halide perovskite films. In particular, the PHI post treatment reduced current at the grain boundaries, facilitated an electron barrier, and reduced trap state density, indicating suppression of leakage pathways and charge recombination, thus passivating the grain boundaries. As a result, a significant enhancement in power conversion efficiency to 20.6% was obtained for the PHI-treated perovskite device in comparison to a control device with 17.4%.

Due to the attraction of fabricating highly efficient tandem solar cells, wide‐bandgap perovskite solar cells have attracted substantial interest in recent years. However, polycrystalline perovskite thin‐films show the existence of trap states at grain boundaries which diminish the optoelectronic properties of the perovskite and thus remains a challenge. Here, we demonstrate a one‐step solution‐processing of the [MA0.9Cs0.1Pb(I0.6Br0.4)3] wide‐bandgap perovskite using Phenylhydrazine Iodide with amino groups to successfully passivate the trap density within grain boundaries and increase the perovskite grain size. The reinforced morphology and grain boundaries treatment considerably enhanced the power conversion efficiency from 12.16% for pristine to 14.63% for the treated devices. This strategy can be easily adopted to other perovskites and help realize highly efficient perovskite solar cells. This article is protected by copyright. All rights reserved.

Charge carrier dynamics and behaviors are key parameters and need to be mapped at the nanoscale in order to search for correct materials for high-performance solar cells. Unfortunately, currently, there are no existing tools or capabilities that can simultaneously map charge carrier dynamics at nanometer range in solar cells. Here we use a Transient Photo-response AFM (TP-AFM) to map for the first time apparent carrier recombination lifetime (τr), transport time (τt) and diffusion length (LD) in hybrid perovskites solar cells. These spatially resolved parameters reveal substantial variations at grain boundaries (GBs) of perovskites. Improved τr, τt and LD at GBs broaden the performance of these state-of-the-art mixed cation perovskites. Detail analysis of these parameters allow us to conclude that reduced density of trap states and recombination in mixed cation perovskites at GBs and its surrounding locations (extending to several nanometers into the grain interior) implies less ion migration. This first of its kind experimental realization of nanoscale mapping of charge carrier dynamics in photovoltaic materials can be used for applications in other optoelectronic devices.

In recent years, hybrid perovskite solar cells (HPSCs) have received considerable research attention due to their impressive photovoltaic performance and low‐temperature solution processing capability. However, there remain challenges related to defect passivation and enhancing the charge carrier dynamics of the perovskites, to further increase the power conversion efficiency of HPSCs. In this work, the use of a novel material, phenylhydrazinium iodide (PHAI), as an additive in MAPbI3 perovskite for defect minimization and enhancement of the charge carrier dynamics of inverted HPSCs is reported. Incorporation of the PHAI in perovskite precursor solution facilitates controlled crystallization, higher carrier lifetime, as well as less recombination. In addition, PHAI additive treated HPSCs exhibit lower density of filled trap states (1010 cm−2) in perovskite grain boundaries, higher charge carrier mobility (≈11 × 10−4 cm2 V−1 s), and enhanced power conversion efficiency (≈18%) that corresponds to a ≈20% improvement in comparison to the pristine devices.

Highly efficient Perovskite solar cells have drawn significant amount of interest of researchers from all over the world due to higher achievable efficiency and low fabrication cost. Hybrid PSC's have emerged as a possible replacement for Si based solar cells. In this paper, different inorganic hole conducting/transporting material have been analyzed with new Electron Transport Layer Zinc OxySulfide (ZnOS) to replace the easily degradable and expensive Spiro-OMETAD. The effect of HPSC's with different types of HCM/HTM are simulated using the software SCAPS-1D. The highest calculated efficiency is 21.04%. The calculations were done considering defects and with interface layers. The results indicate that using inorganic HTMs instead of Spiro-OMETAD is both cost effective and stable. The effect of the various HTMs were calculated against ZnOS as the electron transport layer.

The massive decline in clean energy sources have prompted researchers worldwide to look for alternative sources to meet up with the increasing energy demands. Semiconductor devices play an important role for the construction of such energy producing devices. One such material is Molybdenum Telluride (MoTe 2 ), which has emerged as a viable option to achieve improved cell stability and performance. In this paper, SCAPS-1D simulator was used to conduct the numerical analysis to examine the basic performance parameters (V oc , J sc , FF and conversion efficiency) of an ultra-thin MoTe 2 PV cell. An additional BSF layer Copper Telluride (Cu 2 Te) was incorporated between the absorber layer and back metal contact to achieve an efficient and a stable cell model. The modified cell model showed better cell parameters of 29.13% conversion efficiency, FF = 85.26%, V oc = 0.8825 V, J sc = 387.139395 mA/cm2 at 1.5 μm of absorber layer and BSF layer thickness of 10 nm compared to the baseline structure which displayed parameters of conversion efficiency 15.45%, FF= 56.69%, V oc = 0.7690 and J sc = 354.451474 mA/cm2 without the BSF layer.

In this paper, numerical analysis was done to evaluate the performance of newly modified structure of CdS/CdTe based thin film solar cell. In this proposed cell conventional absorber CdTe layer, back contact Ni was used along with a 500nm thick Cu 2 Te BSF layer. The viability of ultra-thin CdTe absorber layer was examined together with newly added CdS:O layer instead of conventional CdS layer. It was found that the proposed ultra-thin cell have a conversion efficiency of 24.03% (Voc =0.8033V, Jsc = 34.499mA/cm2, FF = 0.8260) which is more efficient than the conventional CdTe thin film solar cell.

This paper has numerically evaluated the performance of a proposed modified structure of thin film solar cell based on CdS/CdTe. In this proposed cell, conventional CdTe layer has been used as absorber, but a new back contact Ni has been used along with newly introduced 100 nm thick ZnO layer to increase the performance of the conventional solar cell. The feasibility of ultra-thin CdTe absorber layer with newly added CdS:O layer instead of conventional CdS layer has also been examined. It has been found that the proposed ultra-thin cell had conversion efficiency of 21.57% (with Voc = 0.89 V, Jsc = 28.32 mA/cm2, and FF = 85.78%). These outcomes have proved the feasibility of the proposed modified CdTe solar cell showing approximately 4.3% more efficiency than the conventional one