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

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

Pyridine Controlled Tin Perovskite Crystallization

Controlling the crystallization of perovskite in a thin film is essential in making solar cells. Processing tin based perovskite films from solution is challenging because of the uncontrollable faster crystallization of tin than the most used lead perovskite. The best performing devices are prepared by depositing perovskite from dimethyl sulfoxide because it slows down the assembly of the tin iodine network that forms perovskite. However, while dimethyl sulfoxide seems the best solution to control the crystallization, it oxidizes tin during processing. This work demonstrates that 4 tert butyl pyridine can replace dimethyl sulfoxide to control the crystallization without oxidizing tin. We show that tin perovskite films deposited from pyridine have a 1 order of magnitude lower defect density, which promotes charge mobility and photovoltaic performanc

A European proficiency test on thin film tandem photovoltaic devices

A round robin proficiency test RR PT on thin film multi junction MJ photovoltaic PV cells was run between 13 laboratories within the European project CHEETAH. Five encapsulated PV cells were circulated to participants for being tested at Standard Test Conditions STC . Three cells were a Si amp; 956;c Si tandem PV devices, each of which had a different short circuit current ratio between the top junction and the bottom one; the remaining two cells were single junction PV devices made with material representative of the individual junctions in the MJ cells. The RR PT s main purpose was to assess the capability of the participating laboratories, in terms of employed facilities and procedures, to test MJ PV devices. Therefore, participant

Superconducting and structural properties of Nb films covered by plasma enhanced chemical vapour deposited a-Si:H layers for superconducting qubit application

With a view to the fabrication of superconducting qubits with low decoherence time, we have investigated the influence of a-Si:H deposition by the plasma enhanced chemical vapor deposition method at 250◦C on the superconducting and structural properties of a 20 nm thick Nb film treated by two surface protection methods: plasma nitridation and deposition of a thin unhydrogenated Si layer. A suppression of theTc and an increase of the residual resistivity are observed due to hydrogen diffusion and decomposition of the native surface oxide, with subsequent oxygen diffusion caused by sample heating. The unhydrogenated Si layer is found to efficiently protect the Nb films against both diffusion processes