A comparative study on low-temperature sol-gel ga-doped zinc oxide inverted PSCs

A low-temperature sol-gel Ga-doped ZnO (ZnO:Ga) thin film as the electron transport layer (ETL) for high efficiency inverted polymer solar cells (PSCs) has been realised. The ZnO:Ga precursor was prepared by dissolving zinc acetate and ethanolamine in the 2-methoxyethanol with Ga(NO3)3 at different concentration. Doped ZnO thin films were deposed on indium tin oxide (ITO)/glass substrates by spin-coating technique and the films annealed at 150°C for 5 minutes in air. To check performances of ZnO:Ga thin film were realized inverted polymer solar cells with the configuration ITO/ZnO:Ga/photoactive layer/MoO3/Ag. The photoactive layer was a blend of poly[(4,8-bis-(2-ethylhexyloxy)-benzo(1,2-b:4,5-b′)dithiophene)-2,6-diyl-alt-(4-(2-octanoyl)-3-fluorothieno[3,4-b]thiophene-)-2-6-diyl)] (PBDTTT-CF) and [6,6]-phenyl C71 butyric acid methyl ester ([70]PCBM) (1:1.5 w/w). In this work was investigated the effect of gallium concentration on the photovoltaic behavior of PSCs. The best efficiency of 7.7% was reached by using a 6 at% ZnO:Ga film as ETL

Optical Performance of Ag-based Back Reflectors with different Spacers in Thin Film Si Solar Cells

Abstract We have compared different Ag-based back reflectors (BRs) applied to superstrate-type microcrystalline Si devices grown on Asahi U glass. In particular, substitution of the conventional ZnO:Al layer by MgF 2 , with lower refractive index and no free-carrier absorption, has been investigated. As electrical issues can mask the optical performance of the BR when evaluated by EQE measurements, a purely optical method that compares the intensity of Raman spectra generated with long wavelength excitation light has been applied. Based on this investigation, MgF 2 /Ag is potentially superior to ZnO:Al/Ag, even when MgF 2 is used in the form of ultrathin layer (few nm, likely island-like). Nevertheless, the novel dual-function n-SiO x /Ag BR outperforms all the other BRs

TCO Optimization in Si Heterojunction Solar Cells on p-type Wafers with n-SiOx Emitter☆

Abstract Silicon heterojunction solar cells have largely demonstrated their suitability to reach high efficiencies. We have here focused on p-type c-Si wafers as absorber, considering that they share more than 90% of the solar cell market. To overcome some of the issues encountered in the conventional (n)a-Si:H/(p)c-Si configuration, we have implemented a mixed phase n-type silicon oxide (n-SiOx) emitter in order to gain from the wider bandgap and lower activation energy of this material with respect to (n)a-Si:H. The workfunction of the transparent conductive oxide layer (WTCO) plays also a key role, as it may induce an unfavourable band bending at the interface with the emitter. We have here focused on AZO, a promising alternative to ITO. Different layers with varying WTCO were prepared, by changing relevant deposition parameters, and were tested into solar cells. The experimental results have been explained with the aid of numerical simulations. Finally, for the n-SiOx/(p)c-Si heterojunction with optimized WTCO a potential conversion efficiency well over 23% has been estimated

Modification of amorphous and microcrystalline silicon film properties after irradiation with MeV and GeV protons

It is well known that the degree of crystallinity has a prominent influence on the stability of Silicon under proton irradiation. Amorphous silicon films are much more stable than mono- or polycrystalline silicon substrates or microcrystalline silicon thin films. In particular it has been shown, that in a micromorph tandem solar cell irradiated with protons in the lower MeV energy range only the microcrystalline diode showed a pronounced decrease in photocurrent after irradiation1. The proton irradiation induced damage in thick crystalline silicon samples has a maximum at beam energies between 1MeV and 4MeV and decreases for further increasing proton energies. However, irradiating an amorphous silicon/crystalline silicon heterojunction solar cell with a relatively dose of 24GeV, we observed a very strong drop in conversion efficiency with only minor recovery after sample annealing. In literature it has been reported 2, that the degradation of amorphous silicon is negligible for proton energies above 100MeV. In order to clarify to which extent also the thin film top layer of the hetero solar cell is affected by the proton irradiation, we exposed a variety of thin film silicon samples either to a 1.7MeV beam with a dose of 5.1012 protons/cm2 or to a 24GeV beam with a dose of 5 .1013 protons/cm2. The investigated intrinsic, p-type and n-type amorphous and microcrystalline silicon films have been deposited by conventional plasma deposition under variation of the silane / hydrogen gas phase ratio. Raman measurements have been done in order to determine the order of crystallinity obtained under various deposition conditions. We observed even at 24GeV a clear modification in the electrical characteristics of the films. Temperature dependent measurements of the dark current revealed in particular for all doped samples a significant increase of the activation energy, that might be explained by a decrease of the dopant efficiency, while for intrinsic a-Si:H layers the increasing activation energy is due to deep defect creation

Procedure Based on External Quantum Efficiency for Reliable Characterization of Perovskite Solar Cells

Perovskite solar cells PSCs have the potential for widespread application, but challenges remain for a reliable characterization of their performance. Standardized protocols for measuring and reporting are still debated. Focusing on the short circuit current density J SC , current voltage characteristics J V and external quantum efficiency EQE are collected to estimate the parameter. Still, they often provide a mismatch above 1 amp; 8201;mA amp; 8201;cm amp; 8722;2, resulting in a possible 5 or higher error. Combining experimental data and optical simulations, it is demonstrated that the EQE can provide a reliable estimate of the J SC that could otherwise easily be overestimated by J V. With access to the internally transmitted light through simulations, an upper limit for EQE is defined depending on the front layers. Details on the origin of the spectral shape and contributions to the optical losses are obtained with further optical simulations, providing hints for cell optimization to achieve a photocurrent gain. The authors use solution processed n i p PSCs with triple cation mixed halide absorbers as demonstrators and ultimately come to the proposal of an upgrade of the present best practices in PSC efficiency measurements. Still, the approach and conclusions are general and apply to cells with all designs and chemical formulation

Scatterometro a sfera integratrice, sensore di posizione e dimensione di oggetti, e relativi metodi di misura

L’invenzione riguarda uno scatterometro a sfera integratrice per la caratterizzazione superficiale di campioni di materiale o la caratterizzazione di diffusione di sorgenti luminose di tipo puntiforme, comprendente: nel caso della caratterizzazione superficiale di campioni di materiale, una sorgente di luce che produce un fascio di luce collimato modulato ad una frequenza f1 che incide sul campione sotto analisi ad un angolo dELTA rispetto alla direzione normale z; e una testa di misura comprendente un fotorivelatore per la rivelazione di una parte di luce diffusa indietro dal campione in risposta a detto fascio di luce collimato, in trasmissione o in riflessione, oppure diffusa dalla sorgente luminosa di tipo puntiforme, caratterizzato dal fatto che detta parte di luce è raccolta da una sfera integratrice presentante una finestra, posta su un asse zeta orientato ad un angolo psi rispetto a detta direzione normale z e a distanza x dal campione o dalla sorgente luminosa di tipo puntiforme, la distanza x potendo assumere anche valori negativi per iquali la sorgente di tipo puntiforme risulta all’interno della sfera integratrice, detta parte di luce essendo raccolta entro un angolo solido omega attorno a detto asse zeta, ovvero entro un semiangolo lineare teta, il fotorilevatore misurando la luce integrata dalla sfera a partire dalla luce raccolta dalla sfera, l’angolo solido omega essendo funzione della distanza x. L’invenzione riguarda altresì un sensore utilizzante lo scatterometro nonché i relativi metodi di misura

Effects of HNO3 molecular doping in graphene/Si Schottky barrier solar cells

Schottky barrier solar cells based on graphene/n-silicon heterojunction have been fabricated and characterized and the effect of graphene molecular doping by HNO3 on the solar cells performances have been analyzed. Different doping conditions and thermal annealing processes have been tested to asses and optimize the stability of the devices. The PCE of the cells increases after the treatment by HNO3 and reaches 5% in devices treated at 200 °C immediately before the exposition to the oxidant. Up to now our devices retain about 80% of efficiency over a period of two weeks, which represents a good stability result for similar devices

Solution-processed indium doped zinc oxide as electron transport layer for inverted polymer solar cells

In this work, we report the synthesis and the application of a low-temperature sol-gel In-doped zinc oxide (IZO) thin film with various indium content as an electron transport layer (ETL) for high efficiency inverted polymer solar cells (PSCs). The IZO precursor was prepared by dissolving zinc acetate and ethanolamine in the 2-methoxyethanol in the presence of InCl3 at different concentration. Doped ZnO thin films were then deposited on indium tin oxide (ITO)/glass substrates by spin coating the above solution and annealed at 150°C for 5' in air. Inverted polymer solar cells with the configuration ITO/IZO/photoactive layer/MoO3/Ag were realized in order to investigate the performance of the IZO thin film. The photoactive layer was a blend of poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] (PTB7-Th) and [6,6]-phenyl C71 butyric acid methyl ester ([70]PCBM). We made a comparative study of the photovoltaic behavior of PSCs realized employing IZO films with various indium contents. The best efficiency of 9.27% was reached using a 1 at% IZO film. The improved performance of such device is due to the better charge collection efficiency of this ETL