Secondary crystalline phases identification in Cu2ZnSnSe4 thin films: contributions from Raman scattering and photoluminescence

In this work, we present the Raman peak positions of the quaternary pure selenide compound Cu2ZnSnSe4 (CZTSe) and related secondary phases that were grown and studied under the same conditions. A vast discussion about the position of the X-ray diffraction (XRD) reflections of these compounds is presented. It is known that by using XRD only, CZTSe can be identified but nothing can be said about the presence of some secondary phases. Thin films of CZTSe, Cu2SnSe3, ZnSe, SnSe, SnSe2, MoSe2 and a-Se were grown, which allowed their investigation by Raman spectroscopy (RS). Here we present all the Raman spectra of these phases and discuss the similarities with the spectra of CZTSe. The effective analysis depth for the common back-scattering geometry commonly used in RS measurements, as well as the laser penetration depth for photoluminescence (PL) were estimated for different wavelength values. The observed asymmetric PL band on a CZTSe film is compatible with the presence of CZTSe single-phase and is discussed in the scope of the fluctuating potentials’ model. The estimated bandgap energy is close to the values obtained from absorption measurements. In general, the phase identification of CZTSe benefits from the contributions of RS and PL along with the XRD discussion.info:eu-repo/semantics/publishedVersio

Untersuchungen an CuIn(Ga)Se_2-Duennschichten und Solarzellen

The following topics were covered: materials properties of CuInGaSe_2, evaporation process, solar cell structure, photoluminescence, positron annihilation, XRD, SIMS, photoelectron spectra, optical properties, defects and phases, tempering of thin films, RTP layers, oxygen influence on the surfaces and volumes, sound treatments of the solar cell structure (WL)SIGLEAvailable from: http://www.iwi-iuk.org/dienste/TheO/ / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Silicon heterojunction metal wrap through solar cells – a 3D TCAD simulation study

Silicon heterojunction metal wrap through solar cells have the potential for high efficiencies in a simple process flow. However, the non-conformal deposition of the hydrogenated amorphous silicon emitter causes specific loss mechanisms of this cell concept. The emitter does not fully cover the inner via surface. As a consequence, the via surface is not passivated and the via metallization is in electrical contact with the silicon base. The resulting loss processes are determined in 3D TCAD simulations. While via related recombination losses are negligible even for highest surface recombination velocities, the resistive losses are found to be critical. The limit for the contact resistance between via metallization and silicon is in the range of 1 Ωcm2, depending on substrate doping and via diameter. Below this value, the cell performance significantly degrades. Finally, three different approaches for novel SHJ-MWT solar cells are discussed

Feasibility study for silicon heterojunction metal wrap through (SHJ-MWT) solar cells

Silicon heterojunction solar cells with efficiencies of up to 24.7 % can be further improved by introducing a metal wrap through metallization. However, silicon heterojunction metal wrap through solar cells suffer from specific loss mechanisms caused by the non-conformal amorphous silicon emitter. The critical mechanisms are resistive and recombination losses in the via. In this work, the recombination at the poorly passivated via surfaces is described theoretically and verified by spatially resolved lifetime measurements using microwave detected photoconductivity. Based on this model, it is shown that the current loss due to via recombination is negligible. However, resistive losses are very critical. A direct electric contact of via metallization and silicon base potentially shunts the cell. To suppress this shunt path, it is suggested to realize the silicon heterojunction metal wrap through solar cell as a back junction cell. In this configuration, the insulation of both contacts becomes very similar to the sequence applied in standard homojunction metal wrap through solar cells. Furthermore, the back junction configuration has the potential for higher efficiencies. AFORS HET simulations show that silicon heterojunction cells could gain up to 3 mA/cm2 in photocurrent when shifting the emitter from front to back side and introducing a dielectric front side passivation

Dielectric backside passivation - improvements by dipole optimization

Based on an examination of interface effects on negative fixed charge formation in Al2O3 we have been able to attribute the charge centroid to the oxide interface between Al2O3 and SiO2. The formation of negative fixed charge seems strongly related to the presence of oriented Al-O-Si bonds, which induce a dipole, causing the negative charge. Improvement of back side passivation should therefore focus on SiO2 interface optimization

P1, P2 and P3 Structuring of CIGSE Solar Cells With a Single Laser Wavelength

Manufacturing of CIGSe thin film solar modules involves typically one laser structuring step P1 and two mechanical structuring steps P2 and P3 for serial interconnection. In our approach, complete laser structuring is successfully demonstrated by application of short nanosecond laser pulses lt;10 ns with a single, visible wavelength of 532 nm. The P1 and the P3 trenches are scribed by induced and direct ablation, respectively. For the P2 scribe, the thermal input of the ns laser pulses is used to transform the CIGSe absorber layer locally into a highly conductive compound to provide proper electrical interconnection. These findings promise further simplification and flexibility to thin film solar cell productio