The intermediate bands (IBs) between the valence and conduction bands play an important role in solar cells. Because the smaller energy photons than the bandgap energy can be used to promote charge carriers transfer to the conduction band and thereby the total output current increases while maintaining a large open circuit voltage. In this paper, the influence of the new band on the power conversion efficiency for the structure of the quantum dots intermediate band solar cell (QDIBSC) is theoretically investigated and studied. The time-independent Schrödinger equation is used to determine the optimum width and location of the intermediate band. Accordingly, achievement of maximum efficiency by changing the width of quantum dots and barrier distances is studied. Theoretical determination of the power conversion efficiency under the two different ranges of QD width is presented. From the obtained results, the maximum power conversion efficiency is about 70.42% for simple cubic quantum dot crystal under full concentration light. It is strongly dependent on the width of quantum dots and barrier distances.

The tremendous amount of research in solar energy is directed toward intermediate band solar cell for its advantages compared with the conventional solar cell. The latter has lower efficiency because the photons have lower energy than the bandgap energy and cannot excite mobile carriers from the valence band to the conduction band. On the other hand, if mini intermediate band is introduced between the valence and conduction bands, then the smaller energy photons can be used to promote charge carriers transfer to the conduction band and thereby the total current increases while maintaining a large open circuit voltage. In this article, the influence of the new band on the power conversion efficiency for structure of quantum dots intermediate band solar cell is theoretically investigated and studied. The time-independent Schrödinger equation is used to determine the optimum width and location of the intermediate band. Accordingly, achievement of a maximum efficiency by changing the width of quantum dots and barrier distances is studied. Theoretical determination of the power conversion efficiency under the two different ranges of QD width is presented. From the obtained results, the maximum power conversion efficiency is about 70.42%. It is carried out for simple cubic quantum dot crystal under fully concentrated light. It is strongly dependent on the width of quantum dots and barrier distances.

A mathematical model of quantum dot intermediate band solar cells (QDIBSCs) is investigated using two intermediate bands (IBs). These two IBs arise from the quantum dot (QD) semiconductor material within the bandgap energy. Some parameters such as the width of the QD (WQD) and the barrier thickness or the inter-dot distances between the QDs (BT) are studied to show their influence on the performance of the QDIBSC. The time-independent Schrüdinger equation, which is solved using the Kronig-Penney model, is used to determine the position and bandwidth energies of the two IBs. In our proposed model, the cubic shape of the QDs from InAs0.9N0.1 and the barrier or host semiconductor material from GaAs0.98Sb0.02 are utilized. It is shown from the results obtained that changing the parameters WQD and BT has more influence on the bandwidth energy for the first IB, Δ1, than in the case of the second IB, Δ2. The optimum power conversion efficiencies (PCEs) of the QDIBSCs with two IBs for the model under study are 58.01% and 73.55% at 1 sun and maximum solar concentration, respectively. One can observe that, in the case of the two IBs, an improvement of the PCE is achieved.

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To make the solar cell technology more competitive as a source of alternative energy, the study of how to improve its efficiency is essential. The detailed balance efficiency of traditional and one-intermediate band solar cell (one-IBSC) is analyzed by using realistic spectra at AM0 and AM1.5 under various light concentrations. Theoretically, the optimum location for one-IB is investigated to determine the maximum efficiency of one-IBSC. The quantum dot (QD) intermediate band solar cell is studied with the effect of some parameters for QD such as width size (QDW) and barrier thickness (BT) to determine the optimum location of one-IB. The main results conclude that the one-IBSC under AM0 spectrum has maximum balanced efficiencies reached to 45.70% and 63.56% for 1 Sun and maximum light concentration, respectively. While for AM1.5 spectrum these efficiencies are 49.35% and 67.60% with the same conditions of AM0 spectrum. The results also show that the maximum balanced efficiencies for one-IBSC nearly achieved when they are processed by QDs which have the main parameters, QDW and BT. V C 2014 AIP Publishing LLC. [http://dx.