Failure analysis in ITO-free all-solution processed organic solar cells

\u3cp\u3eIn this paper we discuss a problem-solving methodology and present guidance for troubleshooting defects in ITO-free all-solution processed organic solar cells with an inverted cell architecture. A systematic approach for identifying the main causes of failures in devices is presented. Comprehensive analysis of the identified failure mechanisms allowed us to propose practical solutions for further avoiding and eliminating failures in all-solution processed organic solar cells. Implementation of the proposed solutions has significantly improved the yield and quality of all-solution processed organic solar cells.\u3c/p\u3

Crystalline silicon solar cell with front and rear polysilicon passivated contacts as bottom cell for hybrid tandems

\u3cp\u3eIn this paper we analyze and model perovskite/c-Si tandem cells with front and rear polySi passivated contacts on the bottom cell. A high-efficiency tandem approach will benefit from the high V\u3csub\u3eoc\u3c/sub\u3e potential of a c-Si bottom cell with front and rear polySi passivated contacts while the combination with a high band gap, semi-transparent, perovskite top cell will largely diminish the UV-Vis parasitic absorption in a polySi front side layer on the c-Si cell. On the other hand since the J\u3csub\u3esc\u3c/sub\u3e is strongly reduced in a tandem bottom cell, free carrier absorption, to which both front and rear polySi layers contribute, will become a relatively more important loss mechanism. We investigate the trade-off between the optical gains and resistive losses from reducing the polySi thickness for cell configurations without transparent conductive oxide (TCO) and also consider the potential of the combination with TCOs. From our optical simulations we conclude that optical losses in the polySi layers of 100 nm and below are limited when applied on the bottom cell. Taking into account resistive losses in the polySi layers of varying thickness the optimal thickness is found to be 50 nm. In combination with the high V\u3csub\u3eoc\u3c/sub\u3e values resulting from the application of polySi passivating contacts this offers a promising route to establish a bottom cell with high efficiency. The combination of very thin polySi with highly transparent TCOs is likely to further improve bottom cell performance.\u3c/p\u3

High-efficiency humidity-stable planar perovskite solar cells based on atomic layer architecture

Perovskite materials are drawing tremendous interest for photovoltaic solar cell applications, but are hampered by intrinsic material and device instability issues. Such issues can arise from environmental influences as well as from the chemical incompatibility of the perovskite layer with charge transport layers and electrodes used in the device stack. Several attempts have been made to address the instability issue, mostly concentrating on the substitution of the organic cations in the perovskite lattice, and on alternatives for the organic charge extraction layers, without laying much emphasis on stabilising the existing, conventional high efficiency methylammonium lead iodide/spiro-OMeTAD based devices. To address the latter issue, we utilized atomic layer deposition (ALD) as a straightforward and soft deposition process to conformally deposit Al2O3 on top of the perovskite absorber. An ultra-thin ALD Al2O3 film effectively protects the perovskite layer while it is sufficiently thin enough to provide a tunnel contact. The fabricated perovskite solar cells (PSCs) exhibit superior device performance with a stabilised power conversion efficiency (PCE) of 18%, a significant reduction in hysteresis loss, and enhanced long-term stability (beyond 60 days) as a function of the unencapsulated storage time in ambient air, under humidity conditions ranging from 40 to 70% at room temperature. PCE measurements after 70 days of humidity exposure show that the devices incorporating 10 cycles of ALD Al2O3 could significantly retard the humidity-induced degradation thereby retaining about 60-70% of its initial PCE, while that of the reference devices drops to a remaining 12% of their initial PCE. This work successfully addresses and tackles the problem of the hybrid organic-inorganic IV-halide perovskite solar cell's instability in a humid environment, and the key findings pave the way to the upscaling of these devices

Highly efficient and stable flexible perovskite solar cells with metal oxides nanoparticle charge extraction layers

\u3cp\u3eIn this study, the fabrication of highly efficient and durable flexible inverted perovskite solar cells (PSCs) is reported. Presynthesized, solution-derived NiO\u3csub\u3ex\u3c/sub\u3e and ZnO nanoparticles films are employed at room temperature as a hole transport layer (HTL) and electron transport layer (ETL), respectively. The triple cation perovskite films are produced in a single step and for the sake of comparison, ultrasmooth and pinhole-free absorbing layers are also fabricated using MAPbI\u3csub\u3e3\u3c/sub\u3e perovskite. The triple cation perovskite cells exhibit champion power conversion efficiencies (PCEs) of 18.6% with high stabilized power conversion efficiency of 17.7% on rigid glass/indium tin oxide (ITO) substrates (comparing with 16.6% PCE with 16.1% stabilized output efficiency for the flexible polyethylene naphthalate (PEN)/thin film barrier/ITO substrates). More interestingly, the durability of flexible PSC under simulation of operative condition is proved. Over 85% of the maximum stabilized output efficiency is retained after 1000 h aging employing a thin MAPbI\u3csub\u3e3\u3c/sub\u3e perovskite (over 90% after 500 h with a thick triple cation perovskite). This result is comparable to a similar state of the art rigid PSC and represents a breakthrough in the stability of flexible PSC using ETLs and HTLs compatible with roll to roll production speed, thanks to their room temperature processing.\u3c/p\u3

Up-scalable sheet-to-sheet production of high efficiency perovskite module and solar cells on 6-in. substrate using slot die coating

\u3cp\u3eScalable sheet-to-sheet slot die coating processes have been demonstrated for perovskite solar cells and modules. The processes have been developed on 6 in. × 6 in. glass/ITO substrates for two functional layers: the perovskite photo-active layer and the Spiro-OMeTAD hole transport layer. Perovskite solar cells produced using these slot die coating processes demonstrate device performances identical to the spin coated devices. All manufactured devices illustrate a high level of reproducibility. The developed slot die coating processes were also used for the manufacturing of perovskite PV modules. Large area modules of 12.5 × 13.5 cm\u3csup\u3e2\u3c/sup\u3e were realized by slot die coating on 6 in. × 6 in. substrates in combination with newly developed laser ablation processes for conventional P1-P2-P3 monolithic cell interconnections. The modules demonstrate power conversion efficiencies above 10%, with a power output of 1.7 W. This achievement is an important milestone in the development of up-scalable manufacturing technologies for perovskite PV modules.\u3c/p\u3

Highly near-infrared-transparent perovskite solar cells and their application in high-efficiency 4-terminal perovskite/c-Si tandems

\u3cp\u3eIn this contribution the development of highefficiency planar semi-transparent perovskite solar cells (STPSCs) for tandem applications is presented. The ST-PSC absorber layer, and electron and hole transport layers were processed using spin coating. The near-infrared (NIR) transmission of the ST-PSC is optimized by improving ITO material quality and tuning the thickness of component layers in cells for optimal light management, leading to a high NIR transmittance of about 93%. In combination with a SunPower IBC cell of 23.8% single-junction efficiency, a 4-terminal (4T) perovskite/c-Si tandem cell efficiency of 26.1% is achieved. In combination with a metal-wrap-through n-PERT c-Si cell laminate of 18.6% efficiency, a 4T perovskite/c-Si tandem cell efficiency of 24.1% is demonstrated, showing that a very significant efficiency gain can be obtained on lower performance c-Si cells.\u3c/p\u3

Towards large area stable perovskite solar cells and modules

\u3cp\u3eIn order to commercialize the perovskite solar cells (PSC) technology, efficient and industrial deposition methods over large areas have to be adopted, and the device architectures have to provide long term stability. In this work we combine several upscalable deposition methods to develop a stable semitransparent PSC. The control of the uniformity of perovskite crystallization by tailoring the ink formulation and the drying process was pursued in order to drastically reduce the efficiency losses over an area increase of 3 orders of magnitude (from 0.04 to 100 cm\u3csup\u3e2\u3c/sup\u3e). When adopting sputtered ITO as top electrode, the stack retains up to 90% of the initial performance after 1000hrs at 85 °C. The use of laser patterning to define P1 P2 and P3 scribes for series interconnected modules enables the fabrication of thermally stable minimodule (4cm\u3csup\u3e2\u3c/sup\u3e) and large module (100cm\u3csup\u3e2\u3c/sup\u3e). Finally an outlook on the use of the perovskite device as top cell in a 4T tandem architecture with commercial c-Si cells will be provided.\u3c/p\u3