Solar RRL最新文献

Halide perovskites are promising as the light absorbers of solar cells with efficient solar power conversion. However, why the degradation of perovskite solar cells (PSCs), especially at high temperatures, happens has not been completely understood to date. Herein, it is shown that evaporation of 4-tert-butylpyridine (4-tBP) from the hole transport layer (HTL) of 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamino)-9,9'-spirobifluorene (spiro-OMeTAD) is one of possible degradation mechanisms in PSCs at a high temperature of 85 °C. In fresh PSCs, the chemical doping of the spiro-OMeTAD HTL with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is not so efficient because of the formation of a LiTFSI:4-tBP complex in the HTL. When PSCs are placed at 85 °C, 4-tBP gradually evaporates from the HTL, resulting in the dissociation of the LiTFSI:4-tBP complex. This 4-tBP evaporation enhances the chemical doping of spiro-OMeTAD by LiTFSI and makes the hole transport level of the spiro-OMeTAD HTL deeper, thereby impeding hole extraction at the perovskite/spiro-OMeTAD/Au interfaces. Herein, the 4-tBP evaporation by covering PSCs with a fluoro-polymer CYTOP layer, significantly improving the high-temperature durability of PSCs, is suppressed. The basic understanding obtained in this study would help promote the spread of more thermally durable PSC products in the future.

Perovskite (PVSK) solar cells offer significant benefits over conventional silicon cells including low-cost solution processibility, minimal materials usage related to strong photon absorption in thin-film cell architectures, and a tunable bandgap. However, PVSK films are mechanically fragile, and fracture of PVSK layers and adjacent interfaces are a significant concern during fabrication, encapsulation, and operation. Herein, a thin-film mechanics fracture analysis tailored for p–i–n and n–i–p PVSK solar cells on both soda lime glass and polyimide substrates fabricated with three PVSK crystallization methods is presented. The role of thermal processing of each cell layer is explored to determine the maximum allowable temperature below which fracture is inhibited. In the analysis, the mechanics basis for processing and materials selection guidelines for preventing fracture in PVSK solar cells is provided.

In the last few years, there have been notable developments in organic solar cells using both small molecule donor and acceptor. It has been noted that adding halogens to the end groups of small molecules could enhance the film structure and, consequently, the performance of the devices. In this study, three novel small molecule donors are created. The molecules include a vinyl-CPDT oligomer with three units, with end-caps made up of indanedione groups and containing four H, four Cl, and four F substituents. The purpose of the study is to investigate how the halogen substituent affects the photovoltaic characteristics of binary devices made with the non-fullerene acceptor (NFA) TOCR2 as the acceptor. Having the halogen in the device enhances its effectiveness, and FG5, which has 4-Cl substituents in the end groups, shows the highest efficiency among all devices with a PCE of 14.39%. Incredibly, the ternary device that is created in normal atmospheric conditions with chloro-substituted FG5 as the donor, TOCR2 as the acceptor, and the wide band gap NFA DICTF as the third element shows significantly improved efficiency, achieving PCE values of up to 16.35%.

As the photovoltaics industry approaches the terawatt (TW) manufacturing scale, the consumption of silver in screen-printed contacts must be significantly reduced for all cell architectures to avoid risks of depleting the global silver supply and substantial cost inflations. With alternative metallization techniques (e.g., plating) facing their own challenges for mass production, advancements in the mainstream screen-printing technology to accelerate the pace of silver reductions are urgently needed. This work presents a silver-lean screen-printed contact scheme, providing scope for substantial reductions in silver consumption based on existing industrial screen-printing capabilities. The initial testing of such a design leads to the fabrication of 24.04% efficient large-area TOPCon solar cells with 9 mg W⁻¹ silver consumption compatible with existing soldering-based interconnection technologies, corresponding to a 25%_rel reduction in silver usage compared to standard industrial screen-printed TOPCon solar cells. Upon further optimization in pattern designs and fabrication processes, this silver-lean design offers a promising pathway toward ultra-low silver consumption of less than 2 mg W⁻¹ for screen-printed TOPCon solar cells without sacrificing efficiency.

Organic Field-Effect Transistors

Dual-acceptor-type multifunctional conjugated polymers based on diketopyrrolopyrrole-dioxo-benzodithiophene have been effectively employed as electron transport layer dopant in high-performance perovskite solar cells and as active channel semiconductor for ambipolar organic field-effect transistors. More in article number 2400185, Chu-Chen Chueh, Tsuyoshi Michinobu, Prashant Sonar, and co-workers.

Flexible Perovskite Solar Cells

In article number 2400243, Seong-Keun Cho, Dong Seok Ham, and co-workers suggest a transparent electrode-integrated flexible barrier substrate as an encapsulation material for protecting perovskite solar cells (PSCs) from air and moisture penetration. The encapsulated PSCs preserved 90% of initial device performance under harsh conditions (60 °C and 90RH%) for over 400 h.

Defects that exist in perovskite semiconductors and at their interfaces with charge transport layers limit the performance of perovskite solar cells (PSCs). Highly sensitive photocurrent measurements reveal at least two sub-bandgap defect states in n–i–p PSCs that use tin oxide covered with [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) as the electron transport layer and tris(4-carbazoyl-9-ylphenyl)amine (TCTA) as the hole transport layer. Semitransparent PSCs with an optical spacer-mirror bilayer on top are used to modulate the interference of light. By varying the thickness of the optical spacer and analyzing the changes in the photocurrent spectra using optical simulations, the defect states that produce photocurrent with sub-bandgap excitation are found to be located near the PCBM-perovskite interface. This conclusion is supported by quasi-Fermi level splitting measurements on perovskite n–i–p half stacks. The observations are explained by an enhanced extraction of trapped electrons from the perovskite at the interface with PCBM.

Perovskite-based triple-junction solar cells have recently gained significant attention and are rapidly developing, thanks to the insights gained from the advancement in its dual-junction counterparts. However, employing perovskite materials in multijunction solar cells with more than two junctions brings new challenges that have not yet been addressed. One aspect is the possibility of reverse bias breakdown of perovskite subcells during operation of the triple–junction device. This is more relevant for triple-junction solar cells because a higher reverse voltage might drop at perovskite subcells compared to the case of dual-junction solar cells. Herein, the breakdown voltages of the two perovskite subcells in perovskite/perovskite/silicon triple-junction solar cells are determined by progressively increasing the reverse bias applied to the subcells in a single-junction architecture during current–voltage measurements and monitoring the appearance of shunts using illuminated lock-in thermography measurements. Furthermore, to analyze the effect on the final triple–junction solar cell, the triple-junction device is brought in different current limitation conditions. It is shown that the subcell breakdown can happen during the operation of the triple-junction solar cell, especially for the case where the perovskite top cell is limiting the overall current of the device. This effect is less severe when the middle perovskite cell limits the current due to the absence of a direct contact with the silver metallization which has shown to be the major degradation site during reverse biasing of perovskite solar cells. Finally, there is no concern regarding breakdown of the silicon bottom cell due to the higher breakdown voltage of silicon compared to perovskite.

As perovskite photovoltaic devices can now compete with silicon technology in terms of efficiency, many strategies are investigated to improve their stability. In particular, degradation reactions can be hindered by appropriate device encapsulation, device architecture, and perovskite formulation. Mesoporous device architectures with a carbon electrode offer a plausible solution for the future commercialization of perovskite solar cells. They represent a low-cost and stable solution with high potential for large-scale production. Several studies have already demonstrated the potential of the mixed 2D/3D ammonium valeric acid iodide-based MAPbI₃ formulation to increase the lifetime of pure MAPbI₃. They can however not describe the mechanisms responsible for the lifetime improvement. Using a full set of characterization techniques in the initial state and as a function of time during damp-heat aging, new insights into the performance and degradation mechanisms may be observed. With (5-AVA)_0.05MA_0.95PbI₃, the solar cells are very stable up to 3500 h and the degradation of performances essentially results from the loss of electrical contacts mainly located at the interfaces. In contrast, for the neat MAPbI₃, a poor stability is evidenced (T50 = 500 h) and the loss in performance results from the degradation of the bulk perovskite layer itself.

The performance and stability of perovskite solar cells rely crucially on the purity of their active perovskite phase. While the two-step method has emerged as a well-known technique for fabricating high-performance cells, it suffers from significant PbI₂ phase impurities at the buried layer due to inefficient diffusion of cationic molecules into the preprepared PbI₂ layer. Herein, a simple yet highly effective method is presented to boost phase purity within the buried layer by introducing formamidinium iodide (FAI) seed molecules into the underlying PbI₂ layer. X-Ray diffraction analysis result reveals that this process significantly reduces the PbI₂ phase and enhances the purity of the perovskite's phase. It is also observed that this technique can produce perovskite layer with a remarkably smooth surface structure and large interconnected crystal grains, forming a continuous layer. These characteristics are subjected to further enhancement when hexamethylenetetramine molecules are concurrently introduced with FAI into the PbI₂ layer. Solar cells fabricated using this method, with an active area of 0.1 cm², achieve a remarkable power conversion efficiency of up to 24.52% with V_oc as high as 1.18 V, representing a substantial improvement over cells produced using the standard two-step method, which attains only 22.18% efficiency. With its simple yet impactful approach, the present method should find widespread adoption in the production of high-performance perovskite solar cells.