Efficient solar energy conversion with CuInS2 thin films is reported. The copper-rich p-type absorber is prepared by thermal coevaporation. A copper to indium ratio between 1.0 and 1.8 can be tolerated with small (≤10%) solar-to-electrical conversion losses. Copper excess phases (CuS) are removed chemically. The cell structure glass/Mo/p-CuInS2/n-CdS/n+-ZnO/Al delivers 10.2% at simulated AM 1.5 conditions. The device properties are discussed based on its energy band diagram.
showed a significant shift in the J-V curves on both branches. In Fig. 2 we display a plot of In J /V 2 vs l/V for a sample containing 6% manganese in fields of 0 and 5 T. For com· parison, we show in Fig. 3 the difference of the tunneling current with and without a 5·T field.The most elegant way to obtain a value for the relative change of the barrier height is by taking the voltage ratio at a constant value of In I /V2. Thus, wee1iminate all dimension· al uncertainties (thickness, electrically active area). Referring to Eq. (I j, it is easily seen that(2)We consequently have chosen an arbitrary value In 1/ V 2 = -12 in Fig. 2. The appropriate values for 1/Vat 0 and 5 T yield (if>H",o/if>H=o)-:::=l -0.67ilV H =0 = 1 -0.67(0.005/0.249) = 0.99. If it is estimated, in addition, that the barrier height if> is 1 eV,6 one obtains immedi· ately the lowering of ¢> to be of 10 ± 5 meV, i.e., the overall Zeeman splitting is 20 ± 10 me V for the conduction band.Therefore, in this compound at 4.2 K, the effective g value for the conduction band is of the order of 30, 15 times larger than for a nonmagnetic semiconductor with an s-like conduction band. The agreement with the results from magnetooptical experiments is excellent, and confirms the validity of the Fowler-Nordheim expression for high electric fields in these compounds.Our work demonstrates that the conduction-band splitting in semi magnetic semiconductors in the presence of an externally applied magnetic field can be observed directly by a simple transport measurement. Spurious effects other than the enhancement of the effective g value through the presence of the Mn dopant may be ruled out because the field shift disappears in pure CdTe. Furthermore, we have shown that Cd l _ x Mn" Te may be fabricated into simple heterostructures in which magnetointernal field emission is observable.The fundamental optical transitions in single crystals ofCulnS 2x Se 2 _ 2x alloys have been studied by electrolyte electroreflectance (EER) spectroscopy. The band gap of the alloys increases nonlinearly with increasing sulphur content corresponding to a bowing parameter 0.14_ The ftatband potential derived from the EER spectra is in excellent agreement with differential capacitance measurements and determined as -0.350 V versus the saturated calomel electrode. CuInS 2x Se 2 _ 2>: liquid junction solar cells are reported that exhibit a long wavelength cutoff in the spectral response matching the EER data.The group I-III-VI 2 compound semiconductors, j.e., the sulphides and selenides, have attracted considerable interest recently. Referring to the position of the fundamental optical transition as well as the extremely steep absorption edge and the high absorption coefficient, these materials should be of particular interest for solar cell applications. For instance, CuInSe 2 /CdS thin-film cells have been fabricated with power conversion efficiencies exceeding 10%. 1 The reliability and performance are strongly affected by the high density of native defects, usually observed in bulk c...
Experimental data on the phase relations in the Cu, In, Se system are presented and the growth of single crystals of CuInSe2 from the melt is described. Hall measurements on both n- and p-type crystals reveal that impurity conduction dominates the low-temperature transport properties. Type conversion by annealing of initially n-type crystals in excess selenium vapor leads to a substantial increase in the compensation level.
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