Electrical and thermal transport properties of synthetic tetrahedrites Cu10TM2Sb4S13 (TM = Mn, Fe, Co, Ni, Zn) and the solid solution Cu12–x Mn x Sb4S13 (0 ≤ x ≤ 2) have been studied in the context of thermoelectric performance. Among these materials, the parent compound Cu12Sb4S13 exhibits the highest power factor, which is primarily derived from a high electrical conductivity. All substituted derivatives display a significant and uniform reduction in thermal conductivity. Within the TM series, the Mn-substituted sample displays the highest ZT (0.8 at 575 K). Changing the Mn concentration to Cu11MnSb4S13 produces the highest ZT, i.e., 1.13 at 575 K. The relatively high value derives from a favorable balance of low thermal conductivity and a relatively high power factor.

In this Letter, we described a solution-processed indium-gallium-zinc oxide thin-film transistors (TFTs) with a solution-processed aluminum oxide phosphate gate dielectric, fabricated at a maximum annealing temperature under 350 °C to be applicable to conventional fabrication process of flat-panel displays (FPDs). The solution-processed TFTs exhibited competitive device characteristics under 350 °C, including a field-effect mobility of 4.50 cm2/Vs, an on-to-off current ratio of ∼109, a threshold voltage of 2.34 V, and a subthreshold gate swing of 0.46 V/dec, making them applicable to the future backplane of FPDs.

used to guide the selection and design of new absorbers using computational techniques. This metric captures the leading physics of absorption relevant to PV efficiency, and it improves upon the simple Shockley-Queisser bandgap model [ 7 ] by considering the full absorption spectrum of the absorber. Hence, SLME should be effective for guiding the selection and design of new ultrathin absorber materials for study and use in drift-aided cells. We have applied the SLME approach to the analysis of all ternary chalcogenides containing Cu, including materials in the system Cu-V-VI. [ 9 ] Several materials were found to exhibit SLME values much higher than those of conventional thin-fi lm absorbers.Subsequently, two general principles were formulated to guide the selection and design of new high-performance absorbers. [ 9 ] In the fi rst case, structural isolation of a Group-V atom in its 5+ oxidation state, e.g., Sb 5+ , within a Cu-rich matrix leads to a narrow Group-V-derived s-orbital band at the conduction band minimum (CBM). In combination with a narrow Cu d band at the valence band maximum (VBM), a high joint density of states and a high absorption coeffi cient ensue. In the second case, if the Group-V atom exists in the lower 3+ oxidation state, e.g., Sb 3+ , it adopts an ns 2 valence electron confi guration. In this 3+ oxidation state, highly asymmetric coordination environments can lead to long distances between the Group-V atoms, resulting in fl at bands and attendant high joint densities of states. These features contribute to an abrupt absorption onset and a high absorption coeffi cient. Strong absorption is reinforced by the parity-allowed nature of the electric-dipole V s or Cu d → V p transition. Hence, the second design principle focuses on structurally isolating the lower oxidation state Group-V element in a semiconducting matrix. Results and DiscussionThese considerations have led us to consider the mineral tetrahedrite, i.e., Cu 12 Sb 4 S 13 , as the basis for a new family of solar absorbers. This material was not revealed as a candidate in the initial SLME search [ 9 ] of Cu-V-VI materials because it was computed to have a zero bandgap, i.e., it is a metal and not a semiconductor. This metallic behavior can readily be appreciated by considering the mixed oxidation-state nature of Cu 12 Sb 4 S 13 . A mixture of formal oxidation states Cu 2+ (d 9 ) and Cu 1+ (d 10 ) is required for charge neutrality, i.e., 10 of the 12 Cu atoms in the chemical formula Cu 12 Sb 4 S 13 are monovalent, while the remaining two Cu atoms are divalent. An incompletely fi lled d-valence band is expected to give rise to the observed degenerate (metallic) behavior, [10][11][12][13] consistent with the Computational inverse design and consequent experimental results allow for the identifi cation of new tetrahedrite-mineral compositions as promising absorber candidates in drift-based thin-fi lm solar cells. In device simulations, cell effi ciencies above 20% are modeled with absorber layers as thin as 250 nm. These new compositio...

To realize the fundamental limits of photovoltaic device efficiency, solar absorbers must exhibit strong absorption and abrupt absorption onsets. Ideally, onsets to maximum absorption (α > 105 cm–1) occur over a few tenths of an electronvolt. First-principles calculations predict CuTaS3 represents a potentially new class of materials with such absorption characteristics. Narrow metallic d bands in both the initial and final states present high joint densities of states and, therefore, strong absorption. Specifically, a mixture of metal d (Cu1+, d 10) and S p characterizes states near the valence band maximum, and metal d (Ta5+, d 0) dominates near the conduction band minimum. Optical absorption measurements on thin films confirm the abrupt onset to strong absorption α > 105 cm–1 at E g + 0.4 eV (E g = 1.0 eV). Theoretical CuTaS3 solar cell efficiency is predicted to be 28% for a 300 nm film based on the metric of spectroscopic limited maximum efficiency, which exceeds that of CuInSe2. This sulfide may offer new opportunities to discover and develop a new class of mixed d-element solar absorbers.

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