In recent years, organometal halide perovskite based photovoltaics have attracted great interest for their high power conversion efficiency (PCE) potentially at low manufacturing cost. Despite the massive progress made by the community, the long-term performance stability and the manufacturability at large scale remain very challenging. In this work, we demonstrate a stable and scalable architecture for perovskite module fabrication. Thermal evaporation assisted 2-step approach is employed for the 1.53 eV perovskite deposition. For high throughput processing, NiOx by linear reactive sputtering is developed as the inorganic hole transport layer (HTL). PCE of 20% is achieved for the solar cell. Perovskite modules with monolithic series interconnected cells by picosecond laser scribing based on the developed cell stack are also fabricated. Above 80% of the initial efficiency is retained after 1000 hrs of thermal mono-stress at 85°C in N2 atmosphere.
Francesco Di Giacomo, Yulia Galagan, Santhosh Shanmugam, Harrie Gorter, Fieke van den Bruele, Gerwin Kirchner, Ike de Vries, Henri Fledderus, Herbert Lifka, Sjoerd Veenstra, Tom Aernouts, Pim Groen, Ronn Andrissen
Organometallic halide perovskite solar cells (PSCs) are extremely promising novel materials for thin-film photovoltaics, exhibiting efficiencies over 22% on glass and over 17% on foil 1, 2 . First, a sheet-to-sheet (S2S) production of PSCs and modules on 152x152 mm2 substrates was established, using a combination of sputtering, e-beam evaporation, slot die coating and thermal evaporation (average PCE of 14.6 ± 1.3 % over 64 devices, more than 10% initial PCE on modules). Later the steps towards a roll-to-roll production will be investigated, starting from the optimization of the stack to make it compatible with a faster production at low temperature. A water based SnOx nanoparticles dispersion was used as solution processable ETL, and the deposition process was scaled-up from spin coating to R2R slot die coating on a 300 mm wide roll of PET/ITO. R2R production is often carried out in ambient atmosphere and involve the use of large volumes of materials, thus a first point is the development of a green solvent and precursor system for the perovskite layer to prevent the emission of toxic compound in the environment. The first results on device fabrication are encouraging, which allow partial R2R manufacturing of flexible PSC (R2R coating of SnOx and perovskite, S2S for Spiro-OMeTAD and gold) with stabilized PCE of 12.6%, a remarkable value for these novel devices. This result can be considered an important milestone towards the production of efficient, low cost, lightweight, flexible PSC on large area.
Tandem solar cells, in which two individual cells are stacked on top of each other, offer the potential to increase the
efficiency significantly compared to a single cell on the same area. To reach maximum efficiency, each cell in the stack
must have a distinctive spectral response and the current in each cell must be similar. This requires smart selection of
materials, proper cell design and appropriate layer thickness. Tandem polymer solar cells can be made by processing two
individual cells from solvent based liquids, separated by a recombination layer. Potential candidates for the
recombination layer are 1) a combination of a ZnO layer and a pH-neutral PEDOT:PSS layer, 2) a TiOx layer combined
with a normal PEDOT:PSS layer. We will discuss the properties of the suggested recombination layers. To determine the
performance of tandem cells, accurate spectral response measurements are crucial. Spectral response measurements of a
polymer tandem cell show that the response of each subcell can be measured only when a bias light with sufficient
intensity and suitable spectrum is applied. We will discuss the special requirements for the spectral response set-up that
are needed in order to successfully discriminate between the responses of each subcell.
In hybrid polymer photovoltaics, conjugated polymers are combined with wide bandgap metal oxide semiconductors like TiO2 or ZnO. Reported maximum power conversion efficiencies (PCE) at AM1.5G conditions for a hybrid polymer bulkheterojunction device are up to 1.6 %. In this paper we report on the current-voltage characteristics of bi-layer devices consisting of TiO2 and a conjugated polymer. Several polymers with different optical bandgap were studied. The maximum External Quantum Efficiency (EQE) of the devices is comparable, but the PCE differs considerably (0.2-0.5%). The differences can for a large part be explained by the differences in optical bandgap of the polymers. It is shown that a low band gap is beneficial for the short circuit current, but does not automatically result in a high PCE as relative shifts of the highest occupied molecular orbital (HOMO) energy levels of the polymers reduce the open circuit voltage (Voc). The calculations show that a PCE up to ~ 19 % can be achieved using the maximum possible Voc and a fill factor of 80%. Judicious engineering of material combinations is required to achieve such a power output, and it expresses the need for a continuing search on potentially low cost, efficient metal oxide/polymer BHJ structures.
KEYWORDS: Polymers, External quantum efficiency, Absorption, Solar cells, Quantum efficiency, Luminescence, Electrodes, Transmission electron microscopy, Photovoltaics, Solar energy
We present a highly fluorescent polymer poly[2,7-(9,9'-dioctylfluorene)-alt-1,4-bis(1-cyanovinyl-2-thienyl)-2-methoxy-5-(3,7-dimethyloctyloxy)phenylene] (PF1CVTP), that was found to perform exceptionally well as electron acceptor in polymer photovoltaic devices when mixed with poly(2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylenevinylene) (MDMO-PPV) as electron donor. The optical and electrochemical properties of the blend were investigated. Both the quenching and the position of the oxidation and reduction waves indicate that charge transfer could take place if the blend is illuminated. Solar cell devices were made of blends containing different ratios of donor and acceptor. Maximum external quantum efficiency of more than 50 % was obtained and a power conversion efficiency of up to 1.5 % was measured under AM1.5 G (100 mW/cm2) conditions.
Polymer bulk hetero junction solar cells were made from poly(2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylene-vinylene) (MDMO-PPV) as donor and poly(cyanoetherphenylenevinylene) (PCNEPV) derivatives as acceptor material. In this paper we start out with discussing the synthesis of the materials. Subsequently, the main issues concerning the devices are treated. Annealing the devices yielded devices with encouraging efficiencies of 0.5% (1 sun, 100mW/cm2), as calculated from the maximum power points (MPP). AFM studies revealed that this anneal step improves especially the interface of the active layer with the under laying PEDOT:PSS, although mobility and morphology changes can not be ruled out. Lowering the molecular weight (Mw) of the MDMO-PPV gave a slight improvement of the device performance. Decreasing the Mw of the acceptor material, MDMO-PCNEPV (PCNEPV derivative with the same side chains as MDMO-PPV) and optimizing the layer thickness led to a device with an efficiency of 0.65%. Finally we looked into the influence of the nature of the side chains on the acceptor polymer. The results suggest that the closer the resemblance between donor and acceptor is the better the device performance.
S. Veenstra, George Malliaras, Hendrik-Jan Brouwer, F. Esselink, Victor Krasnikov, Paul van Hutten, Jurjen Wildeman, H. Jonkman, George Sawatzky, Georges Hadziioannou
Large photovoltaic responses have been recently observed in devices based on conjugated polymer-C60 blends. Their enhanced performance, which relies on the formation of a bicontinuous network of donor-acceptor heterojunctions, is very sensitive to the morphology of the blend. In this paper, we propose sexithiophene-C60 blends, prepared by coevaporation, as a model system for the study of these devices. Preliminary results suggest a microphase-separated morphology with a domain size comparable to the exciton diffusion length. A photovoltaic device with quantum efficiency of 1% is demonstrated.
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