SolarTR-2 Solar Electricity Conference and Exhibition November 7-9, 2012 Antalya, Turkey 1 Introducing High Efficiency Solar Cells Based on Crystalline Silicon Doped with Transition Metals A. Rostami 1,2 , H. Heidarzadeh 2 , H. Baghban 1 , M. Dolatyari 1 , and H. Rasooli 3 1 School of Engineering-Emerging Technologies, University of Tabriz, Tabriz, Iran 2 Department of Electrical and computer Engineering, University of Tabriz, Tabriz, Iran 3 Islamic Azad University, Tabriz Branch, Tabriz, Iran Corresponding author: rostami@tabrizu.ac.ir Abstract: Solar cell materials with more than one bandgap offer the possibility to increase the efficiency of the solar cell beyond that of a single bandgap cell. In the intermediate bandgap solar cell (IBSC) an intermediate narrow metallic band (IB) is placed in the traditional forbidden bandgap which extends the absorption spectrum. This generates extra electron–hole pairs and thus increases the current without decreasing the output voltage and therefore increases the quantum efficiency. Substitution of transition metal atoms (TM) in the crystalline silicon may give rise to a type of high- efficiency photovoltaic materials with intermediate bands to absorb low energy photons. In the present study comprehensive analysis is carried out on this kind of materials. Theoretical studies confirm the formation of suitable mini-bands within silicon band gap by doping of transition metals in crystalline silicon. The mini bands mainly are created by nd orbitals of the transition metals. Absorption coefficient, density of states and band structure are three important features of the proposed materials. Here, we calculated these characteristics for the crystalline silicon doped with TM=Ti, Zr, Hf, Cr, Mo, W, Fe, Ru, Os as candidates for presenting an isolated partially-filled narrow bands between the valance band and the conduction band of silicon. The results show that a crystalline silicon solar cell with an intermediate band located at 0.35eV below the conduction band or above the valence band can reach a limiting efficiency of 44%, improving greatly than 31% of the Shockley–Queisser limit for the single junction Si solar cell. Ti doped silicon can be create this band between the valance band and conduction of silicon. Keywords: high efficiency solar cell, intermediate band, silicon, metal-doped silicon