The Non-Innocent Role of Hole-Transporting Materials in Perovskite Solar Cells

The race to the future generation of low-cost photovoltaic devices continuouslytakes on added momentum with the appearance of novel practical solutions forthe fabrication of perovskite solar cells (PSCs), a paradigm technology forultracheap light-to-electricity conversion. Much has been done in the past fewyears toward defining standard protocols for the assessment of their efficiencyand stability, aiming at achieving a worldwide consensus on the issue, that willallow reliable reporting of new data. While this is undoubtedly a step aheadtoward commercialization of these devices, it also often triggers researchers totest record architectures using benchmark configurations, mainly for whatregards the ancillary layers that extract electrical charges from the photoexcitedperovskite. In particular, the mostly used hole-transporting material (HTM) is thesmall-molecule spiro-OMeTAD, which is also well known to be the origin of PSCdegradation after prolonged operation. Herein, it is aimed to remark the hugeimpact of the HTM on PSC performance, recalling major issues associated withthe conventional spiro-based one and providing an overview of state-of-the-artalternatives. Finally, possible scenarios for the future development of smartHTMs are also envisioned, as charge-extracting layers, with a real active role inensuring PSC operational stability

Crosslinked fluoropolymers exhibiting superior high-temperature energy density and charge-discharge efficiency

Superior high-temperature discharged energy densities in comparison to those of the current dielectric polymers have been demonstrated in the crosslinked fluoropolymers

An Efficient and Effective Design of InP Nanowires for Maximal Solar Energy Harvesting

Abstract Solar cells based on subwavelength-dimensions semiconductor nanowire (NW) arrays promise a comparable or better performance than their planar counterparts by taking the advantages of strong light coupling and light trapping. In this paper, we present an accurate and time-saving analytical design for optimal geometrical parameters of vertically aligned InP NWs for maximal solar energy absorption. Short-circuit current densities are calculated for each NW array with different geometrical dimensions under solar illumination. Optimal geometrical dimensions are quantitatively presented for single, double, and multiple diameters of the NW arrays arranged both squarely and hexagonal achieving the maximal short-circuit current density of 33.13 mA/cm2. At the same time, intensive finite-difference time-domain numerical simulations are performed to investigate the same NW arrays for the highest light absorption. Compared with time-consuming simulations and experimental results, the predicted maximal short-circuit current densities have tolerances of below 2.2% for all cases. These results unambiguously demonstrate that this analytical method provides a fast and accurate route to guide high performance InP NW-based solar cell design

Understanding the Impact of Cu-In-Ga-S Nanoparticles Compactness on Holes Transfer of Perovskite Solar Cells

Although a compact holes-transport-layer (HTL) film has always been deemed mandatory for perovskite solar cells (PSCs), the impact their compactness on the device performance has rarely been studied in detail. In this work, based on a device structure of FTO/CIGS/perovskite/PCBM/ZrAcac/Ag, that effect was systematically investigated with respect to device performance along with photo-physics characterization tools. Depending on spin-coating speed, the grain size and coverage ratio of those CIGS films on FTO substrates can be tuned, and this can result in different hole transfer efficiencies at the anode interface. At a speed of 4000 r.p.m., the band level offset between the perovskite and CIGS modified FTO was reduced to a minimum of 0.02 eV, leading to the best device performance, with conversion efficiency of 15.16% and open-circuit voltage of 1.04 V, along with the suppression of hysteresis. We believe that the balance of grain size and coverage ratio of CIGS interlayers can be tuned to an optimal point in the competition between carrier transport and recombination at the interface based on the proposed mechanism. This paper definitely deepens our understanding of the hole transfer mechanism at the interface of PSC devices, and facilitates future design of high-performance devices

The Impact of Hybrid Compositional Film/Structure on Organic–Inorganic Perovskite Solar Cells

Perovskite solar cells (PSCs) have been intensively investigated over the last several years. Unprecedented progress has been made in improving their power conversion efficiency; however, the stability of perovskite materials and devices remains a major obstacle for the future commercialization of PSCs. In this review, recent progress in PSCs is summarized in terms of the hybridization of compositions and device architectures for PSCs, with special attention paid to device stability. A brief history of the development of PSCs is given, and their chemical structures, optoelectronic properties, and the different types of device architectures are discussed. Then, perovskite composition engineering is reviewed in detail, with particular emphasis on the cationic components and their impact on film morphology, the optoelectronic properties, device performance, and stability. In addition, the impact of two-dimensional and/or one-dimensional and nanostructured perovskites on structural and device stability is surveyed. Finally, a future outlook is proposed for potential resolutions to overcome the current issues