At the end of 2017 roughly 1.8% of the worldwide electricity came from solar photovoltaics (PV), which is foreseen to have a key role in all major future energy scenarios with an installed capacity around 5 TW by 2050. Despite silicon solar cells currently rule the PV market, the extremely more versatile thin film-based devices (mainly Cu(In,Ga)Se₂ and CdTe ones) have almost matched them in performance and present room for improvement. The low availability of some elements in the present commercially available PV technologies and the recent strong fall of silicon module price below 1 $/W_p focused the attention of the scientific community on cheap earth-abundant materials. In this framework, thin film solar cells based on Cu₂ZnSnS₄ (CZTS) and the related sulfur selenium alloy Cu₂ZnSn(S,Se)₄ (CZTSSe) were strongly investigated in the last 10 years. More recently, chalcogenide PV absorbers potentially able to face TW range applications better than CZTS and CZTSSe due to the higher abundance of their constituting elements are getting considerable attention. They are based on both MY₂ (where M = Fe, Cu, Sn and Y = S and/or Se) and Cu₂XSnY₄ (where X = Fe, Mn, Ni, Ba, Co, Cd and Y = S and/or Se) chalcogenides. In this work, an extensive review of emerging earth-abundant thin film solar cells based on both MY₂ and Cu₂XSnY₄ species is given, along with some considerations on the abundance and annual production of their constituting elements.

Photoluminescence (PL) and deep level transient spectroscopy (DLTS) measurements were used to study the origin of optical emissions in the 0.8–1.0 eV region of selected oxygen precipitated and dislocated silicon samples. It was shown that the D1 band, present in both types of samples, is the convolution of different sub-bands, narrowly spaced between 0.802 and 0.820 eV. The emission at 0.807 eV, assigned in the literature to dislocations, was found only in samples where dislocations were intentionally generated by plastic deformation or induced by the clustering of self-interstitials generated during the growth of oxide precipitates. A comparison of the results of PL, DLTS, and optical DLTS measurements allows the assignment of levels involved in the radiative recombination processes.

In this work we present a study of a p-type Czochralski-grown Si ingot which was grown using 10% solar grade silicon (SoG-Si). As the SoG-Si contains a relatively high concentration of impurities including phosphorus, the electrical properties of the as-grown wafers from this ingot are affected by both the compensating dopants and other impurities. Measurements of the minority charge carrier lifetime in the as-grown material reveal very low values (4–8μs). The Hall mobilities at room temperature correspond to normal values for Czochralski silicon in the upper part of the ingot (which solidifies first) and decrease significantly toward the bottom of the ingot. Segregation leads to an accumulation of impurities toward the lower parts of the ingot as well as to a stronger increase in phosphorus than of boron, the latter of which results in a high compensation level (i.e., an increasing resistivity). A priori, both effects could be responsible for the degradation of the electrical properties in the lower parts of the ingot, whereas theoretical considerations show that the level of compensation should not cause a strong decrease in Hall mobility at room temperature. Untextured solar cells have been processed from wafers originating from different positions of the ingot. As expected, the phosphorus diffusion leads to a gettering effect: the recombination active impurities are removed out of the wafer volume. This results in relatively high efficiencies (>16%) of the solar cells but does not show a strong correlation between ingot height and cell efficiency. This observation is also confirmed by the high bulk lifetimes (>200μs) measured after the process even for samples originating from the last solidified (lower)part of the ingot. The Hall mobility of samples cut from finished solar cells has been measured and shows the same trend as the as-grown samples, the values for the bottom of the ingot still being very low. With the concentrations of boron and phosphorus studied up to this point, compensation showed no detrimental effect on the cell efficiency of industrial-like solar cells.