• Energy Research

Abstract We report on the theoretical investigation of a silicon-based interdigitated back contact back heterojunction (BHJ) solar cell that combines the advantages of heterojunction with intrinsic thin layer (HIT) solar cell and point contact back junction c-Si solar cell. Our results show an optimum bandgap for emitter (p-type a-Si:H) layer for this cell to be approximately 1.72 eV. As we increase the bandgap from 1.3 eV to 2.2 eV, the open circuit voltage (Voc) increases from 0.45 V to 0.75 V and then saturates, while the short circuit current density (Jsc) remains constant at 35 mA/cm2 up to about 2.0 eV, and then decreases to zero. Fill factor (FF) increases from 57% to a maximum of 75% as the bandgap increases from 1.3 eV to ∼1.72 eV, respectively, and then decrease to 5% when the bandgap reaches 2.1 eV. Efficiency increases from 7% and reaches a maximum of about 19% at around 1.7 eV and then decreases to zero at 2.1 eV. These results can be correlated to changes in valance band spike (barrier) when emitter bandgap increases from 1.3 eV to 2.2 eV, and are explained in terms of band alignment between p-a-Si:H/i-a-Si:H/n-type-c-Si.

Abstract The paper reports on the simulation studies of silicon based point contact back heterojunction solar cells using Silvaco Atlas tools. We also make use of band alignment diagrams connecting the entire cross-section of the device, from the emitter to the back surface field, to appreciate the operation of the solar cell. The effect of bias conditions on the band diagram and solar cell performance is explored. The influence of doping in the a-Si:H layer on the performance parameters is also investigated. In performing our investigation, we consider an optimized solar cell that shows a high efficiency of 24.49%, with a Voc of 0.76 V, Jsc of 38.29 mA/cm2, and FF of 84.2. Further improvements in efficiency can be potentially achievable by using texturization and front surface field.

Abstract This paper reports the fabrication of c-Si based solar cells using spin-on dopants. Solar cells were developed by texturing both surfaces of the c-Si, and forming the p–n junction by spin-coating the n-type dopant followed by rapid thermal processing (RTP). For back surface field formation on the rear side, a similar spin-coating step was undertaken for one cell and e-beam Al deposition for the other. In the case of double-sided spin-coated cell, simultaneous p–n junction and back surface field were formed in one RTP cycle. Without using high performance features in the device, double-sided spin-on doped cell showed Voc of 600 ± 0.01 mV, Jsc of 33.1 ± 0.03 mA/cm2, FF of 74.26 ± 0.06% and efficiency of 14.74%. As compared to single-sided spin-on doped cell, an improvement in efficiency of about 1.3% has been obtained which can be attributed to boron back surface field. Double-sided spin-on process significantly reduces thermal budget and improves throughput. Besides texturization, high efficiency features have not been used in the device. The results clearly demonstrate that c-Si based solar cells are potentially cost effective to manufacture.

Abstract Tandem organic photovoltaic (TOPV) cell is one of the technologies to harvest more solar power by staking two or more OPV devices on top of each other. Recently, the highest power conversion efficiency (PCE) ever achieved was 17.3%. Herein, this paper simulates the response of 676‬ different TOPV devices that consists front and back OPV cells. For this purpose, this paper uses the best 26 single-cell OPV devices to form the TOPV front and back cells combinations. The results show that there are some new TOPVs that can exceed 17.3% efficiency limit for TOPV. Also, in this work thickness optimization was performed for these new TOPV devices with an objective of efficiency maximization. As a result, using PBDTS-TDZ: ITIC in the front cells and PTB7-Th: O6T-4F:PC71BM in the back cell gives 18.6% efficiency. Likewise, the TOPV of PBDB-T-2F:TfIF-4FIC in the front cell with PTB7-Th:O6T-4F:PC71BM in the back cell gives 18.06% efficiency.

Copper indium gallium selenide (CIGS) based solar cells are receiving worldwide attention for solar power generation.