Theoretical analysis of GaN-based semiconductor in changing performanc of perovskite solar cell

Abstract

GaN-based semiconductor has been used in optoelectronics and electronic devices. It is a new research topic at present that how to combine its good electrical properties to explore other applications in theory or experiment. In this paper, SCAPS-1D software is used to calculate the theoretical mechanism of GaN electron transport in FTO/GaN/ (FAPbI<sub>3</sub>)<sub>0.85</sub>(MAPbBr<sub>3</sub>) <sub>0.15</sub> /HTL perovskite solar cell (PSC) structure. The results showed that when GaN was used in PSC, the <i>V<sub>oc</sub></i> increased from 0.78V to 1.21V, PCE increased from 15.87% to 24.18% and the small conduction band cliff formed between GaN and the active layer could improve the efficiency of the cell. By calculating the Quasi-Fermi level splitting, interfacial electric field, interfacial recombination rate and depletion zone thickness at different doping concentrations and thickens, the influences of GaN thickness and doping concentration on open-circuit voltage and other device parameters were analyzed, and the physical mechanism of GaN as an electron transport layer was discussed. With the increase of the thickness, the J<sub>sc</sub> of this solar cell decreased gradually, but the change range was feebleness (24.13 mA/cm<sup>2</sup>~ 23.83mA/cm<sup>2</sup>). The <i>V<sub>oc</sub></i> decreased from 1.30V to 1.21V when the thickness of GaN exceeded 100nm, and then remained stable. The power conversion efficiency changing regularity of the form of "pits" appears——first decreases, then increases, and finally maintains stability, with the highest efficiency of 24.76% and the corresponding GaN thickness of 245nm.The FF showed a trend of first decreasing, then increasing, and finally leveling off. When the doping concentration and thickness change at the same time, with the increase of doping concentration, the J<sub>sc</sub> decreases gradually with the increase of thickness, but the overall change range is small, and the open-circuit voltage, filling factor and conversion efficiency all show "pits" changes. When the thickness of GaN is 200nm, with the concentration of gallium nitride doping increasing, the Quasi Fermi level splitting increasing, and the strength of the built in electric field between the active layer and the GaN layer increases, thus providing a greater driving force for carrier separation, resulting in a larger potential difference Δμ, and thus a larger V<sub>oc</sub>. With the increase of doping concentration, the recombination rate of the active layer/GaN layer interface and the recombination rate inside the active layer increase, which leads to the decrease of J<sub>sc</sub>. It is found that the position of the "Concave point" of V<sub>oc</sub> under the change of gallium nitride thickness is determined by the variation of GaN doping concentration is determined by the width of GaN depletion region between GaN/FTO, and the width of GaN depletion region between GaN/active layer determines the width of the whole “pit”. In summary, the cell parameters can be improved by simultaneously changing the thickness and doping concentration of GaN.