Single junction a-Si:H solar cell with a-Si:H/nc-Si:H/a-Si:H quantum wells

A single junction hydrogenated amorphous silicon (a-Si:H) solar cell with incorporating hydrogenated nanocrystalline silicon (nc-Si:H) and a-Si:H (nc-Si:H/a-Si:H) multiple quantum wells (MQW) in the intrinsic region is proposed. Its theoretical realization has been made on the basis of existing quantum well solar cell models to determine the influence of the incorporated MQW over the conversion efficiency of a-Si:H solar cell. The atomic energy states and density of states of nc-Si:H/a-Si:H quantum wells (QW) are simulated at various QW widths. Based on the simulated results the absorption coefficient of nc-Si:H/a-Si:H QW is estimated and these values along with the evaluated atomic energy states of QW are used to optimize the QW width for the designed quantum well solar cell. The optimum well width is found to be 10nm, where the absorption coefficient increases in three steps starting from 1.0 x 10(4) cm(-1) to 3.0 x 10(4) cm(-1) for photon energy of 1.2 eV to 1.4 eV, respectively, and thereafter remained constant for higher energies. The estimated absorption coefficient of 10 nm QW is involved in the calculations of photocurrent density to study the effect of number of incorporated QW on short circuit current density (J(SC)), open circuit voltage (V-OC) and efficiency (eta) of a-Si:H solar cell. The J(SC), V-OC, and eta are presented for up to 100 QW incorporated a-Si:H solar cell. The results show that the conversion efficiency of a-Si:H solar cell is directly related to the number of incorporated QW, which is mainly due to the growing short circuit current density with increasing number of QW. The current-voltage plot for 100-QW a-Si:H solar cell with intrinsic region of 5.5 mu m showed a peak power of 13.3 mW/cm(2). (C) 2013 Elsevier B.V. All rights reserved.