Optical Optimization of the TiO2 Mesoporous Layer in Perovskite Solar Cells by the Addition of SiO2 Nanoparticles

Preparation of Low Grain Boundary Perovskite Crystals with Excellent Performance: The Inhibition of Ammonium Iodide

For the study, we prepared a low grain boundary three-dimensional CH3NH3PbI3 crystal (3D-MAPbI3) on TiO2 nanoarrays by inhibition of ammonium iodide and discussed the formation mechanism of the crystal. Based on the 3D-MAPbI3 crystal, solar cells showed modified performance with a power conversion efficiency (PCE) of up to 19.3%, which increases by 36.8% in contrast to the counterparts. We studied the internal photocurrent conversion process. The highest external quantum efficiency is up to 92%, and the electron injection efficiency is remarkably facilitated where the injection time decreases by 37.8% compared to the control group. In addition, based on 3D-MAPbI3, solar cells showed excellent air stability, which possesses 78.3% of the initial PCE, even though they were exposed to air for 30 days. Our results demonstrate a promising approach for the fabrication of perovskite solar cells with high efficiency and stability.

Photon management to reduce energy loss in perovskite solar cells

Despite the rapid development of perovskite solar cells (PSCs) over the past few years, the conversion of solar energy into electricity is not efficient enough or cost-competitive yet. The principal energy loss in the conversion of solar energy to electricity fundamentally originates from the non-absorption of low-energy photons ascribed to Shockley-Queisser limits and thermalization losses of high-energy photons. Enhancing the light-harvesting efficiency of the perovskite photoactive layer by developing efficient photo management strategies with functional materials and arrays remains a long-standing challenge. Here, we briefly review the historical research trials and future research trends to overcome the fundamental loss mechanisms in PSCs, including upconversion, downconversion, scattering, tandem/graded structures, texturing, anti-reflection, and luminescent solar concentrators. We will deeply emphasize the availability and analyze the importance of a fine device structure, fluorescence efficiency, material proportion, and integration position for performance improvement. The unique energy level structure arising from the 4fn inner shell configuration of the trivalent rare-earth ions gives multifarious options for efficient light-harvesting by upconversion and downconversion. Tandem or graded PSCs by combining a series of subcells with varying bandgaps seek to rectify the spectral mismatch. Plasmonic nanostructures function as a secondary light source to augment the light-trapping within the perovskite layer and carrier transporting layer, enabling enhanced carrier generation. Texturing the interior using controllable micro/nanoarrays can realize light-matter interactions. Anti-reflective coatings on the top glass cover of the PSCs bring about better transmission and glare reduction. Photon concentration through perovskite-based luminescent solar concentrators offers a path to increase efficiency at reduced cost and plays a role in building-integrated photovoltaics. Distinct from other published reviews, we here systematically and hierarchically present all of the photon management strategies in PSCs by presenting the theoretical possibilities and summarizing the experimental results, expecting to inspire future research in the field of photovoltaics, phototransistors, photoelectrochemical sensors, photocatalysis, and especially light-emitting diodes. We further assess the overall possibilities of the strategies based on ultimate efficiency prospects, material requirements, and developmental outlook.

High-performance hole conductor-free perovskite solar cell using a carbon nanotube counter electrode

Carbon-based perovskite solar cells (C-PSCs) are the most promising photovoltaic (PV) due to their low material and manufacturing cost and superior long-term stability. This work compares the performance between gold (Au) and multi-wall carbon nanotube (MWCNT) electrodes for hole transport material (HTM)-free PSCs. Based on the obtained results, C-PSCs showed remarkable power conversion efficiency (PCE) and negligible hysteresis. Indeed, under optimized conditions, MWCNTs demonstrated superior performance as a counter electrode (CE) for HTM-free PSCs, leading to a PCE of 15.56%, which is comparable to the current state-of-the-art materials. Also, the presence of MWCNTs in the cell architecture enhances the collection and injection of holes at the perovskite/MWCNT interface and as a result, improves the external quantum efficiency (EQE) and current density because the recombination process is quenched. This improvement is confirmed by impedance spectroscopy (EIS), photoluminescence (PL), current/voltage (J–V), and EQE measurements. Moreover, MWCNTs could act as a protective layer and enhance the PSC stability. C-PSC was more stable than that of traditional PSC based on Au, which could maintain 80% of its primary PCE for long-periods of storage in moist conditions.

Carbon-based perovskite solar cells (C-PSCs) are the most promising photovoltaic (PV) due to their low material and manufacturing cost and superior long-term stability.

Stability Improvement of Perovskite Solar Cells for Application of CuInS2 Quantum Dot-Modified TiO2 Nanoarrays

In this work, we developed a CH₃NH₃PbI₃ perovskite solar cell with CuInS₂ quantum dot-modified TiO₂ nanoarrays (TiO₂-CuInS₂ QD-NAs) as a scaffold layer. Based on the suitable device configuration, we achieved improved power conversion efficiency (PCE) of 13.3%, which was 38.3% higher than that of the device without QD modification (8.2%). After exposure to air for 30 days, the TiO₂-CuInS₂ QD-NA-based device possessed a PCE of 5.4%, being 41% of the original performance, which was far superior to that of TiO₂ nanoarray-based solar cells with a PCE of 1.1%. Our results showed that the crystallinity of perovskite, surface state, and interface for charge transport of TiO₂-CuInS₂ QD-NA-based perovskites all remarkably improved, indicating the improved air stability for TiO₂-CuInS₂ QD-NA-based solar cells.