The search for Pb-free perovskite materials continues with limited success to find a suitable replacement for Pb with outstanding optoelectronic properties. Here we report Pb-free inorganic halide perovskite Cs 2 PtI 6 with excellent absorption coefficient, long minority carrier lifetime and optical bandgap of 1.4 eV. Atmospheric precursor based solution processing results in high quality Cs 2 PtI 6 with absorption coefficient of 4 10 � �� for photon energies > 1.5 eV and high minority carrier lifetimes of > 2 s indicating low defect density in the material. Superstrate n-i-p solar cells processed with the structure F:SnO 2 /CdS/Cs 2 PtI 6 /carbon/Cu show promising device efficiency of 13.88%. These planar devices processed under atmospheric conditions show low V oc deficit (< 0.3 V) without any hysteresis in forward and reverse scans indicating low trap densities. Pt offers an excellent model system for replacement of Pb due to high atomic number, oxidation resistance and stability. Cs 2 PtI 6 is an atmospherically stable phase under AM1.5G and 65 C upto 1000 hours.Organic-inorganic hybrid halide perovskite solar cells (HPSCs) have attracted immense attention because of excellent optoelectronic properties and record power conversion efficiency (PCE) has reached 25.2% from 3.8% within a few years. [1][2][3][4][5][6] Despite the very high efficiency already attained by HPSCs (ABX 3 ; A = MA, FA, Cs; B = Pb, Sn; X=I, Br, Cl) resulting from high absorption coefficient and electron-hole diffusion lengths; toxicity of Pb and stability of these materials are veritable issues. Replacing MA + and FA + with PEA + , BA + , Cs + has shown to enhance the stability of hybrid perovskite solar cells against thermal and moisture related degradation. [7][8][9][10][11] The superior optoelectronic properties of Pb-based halide perovskites are attributed to the inactive Pb 6s orbitals, and can be replaced by Ge 2+ , Sn 2+ , Sb 3+ , Bi 3+ , Cu 2+ with inactive s orbitals. Replacement of Pb 2+with Sn 2+ and Ge 2+ seems to be a logical solution for addressing the toxicity issues and results in excellent optoelectronic properties such as high absorption coefficient, high hole mobility resulting Accepted Article replacement for Pb with outstanding optoelectronic properties.

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The optimal fraction of Mg incorporation in sputter‐deposited MgXZn1−XO (MZO) emitters for thin‐film CdTe‐based solar cells is evaluated by varying it over a range of x from 0 to 0.35. This range allows a variation in the conduction band offset from −0.1 eV (cliff like) to +0.32 eV (spike like). A maximum efficiency of 18.5% for cells with the bilayer CdSeTe/CdTe absorber occurs at x = 0.15, which corresponds to a spike‐like band offset near 0.2 eV, as confirmed by X‐ray photoelectron spectroscopy. In addition, good cell performance is seen over a fairly broad range of x extending from 0.1 to 0.25. The MZO optical bandgap increases with the Mg fraction, consistent with an increasing conduction band offset. Temperature‐dependent current−voltage measurements and time‐resolved photoluminescence show improvement in the emitter/absorber interface with the incorporation of Mg. Capacitance−voltage measurements show that the depletion region extends further into the absorber with more Mg, and X‐ray diffraction confirms a change from a hexagonal‐dominant crystal structure toward zinc blende at x = 0.35.

The electronic structure and linear optical properties of the pyroborate A 2 B 2 O 5 (A ) Mg, Ca, Sr) compounds are reported here. These compounds, which crystallize with four formula units in the monoclinic space group P2 1 /c, are modeled in terms of the cluster units (A 2 B 2 O 5 ) 2 . The calculated electronic structures show that the top of the valence band consists of mostly the O-2p orbitals and the bottom of the conduction band consists of cationic orbitals. The dynamic refractive indices of these pyroborates are obtained in the framework of the INDO/ SCI approximation together with the sum-over-states method. It is found that the refractive index increases with an increase of alkaline-earth cationic radius for pyroborates, and the charge-transfer for O 2anion orbitals to A 2+ cation orbitals appears to provide a significant contribution to the linear polarizability of these compounds.