AC analysis of temperature effects on conversion efficiency of CuInGaSe ₂ solar cells

Abstract

The temperature effect on a CuInGaSe 2 (CIGS) solar cell was investigated in the temperature range −10 to 80°C using direct current (DC) and alternating current (AC) characteristic analysis of CIGS solar cells. The change rates of short-circuit current density (J sc ), open-circuit voltage (V oc ), fill factor (FF) and efficiency (η) with respect to temperature were investigated. In addition, the variation of impedance, total capacitance and dynamic resistance due to the temperature change implied that the width of the depletion region in a p-n junction shrank, and the effective minority carrier lifetime (τ eff ) decreased. Consequently, J sc changed slightly due to the balance between the variation of the energy bandgap (E g ) and τ eff . However, V oc linearly decreased due to the relationship of E g when the temperature increased. From these results, it has been concluded that V oc plays an important role in the characteristics of the CIGS solar cell with change of temperature.Introduction: CuInGaSe 2 (CIGS) materials have been of interest for photovoltaic applications because of their high absorption coefficient (∼10 4 / cm), adjustable direct bandgap (1.0-1.4 eV) and high stability for light radiation [1][2][3][4]. These properties enable CIGS solar cells to have high efficiency, low cost and high stability. Currently, the efficiency of CIGS solar cells has been obtained above the value of 20% and also the efficiency in flexible CIGS solar cells has already reached a value of 17% at the research level [3,4]. A CIGS solar cell device is a hetero-junction semiconductor with an n-type CdS/ZnO layer, and this means the CIGS solar cell is sensitive to temperature like other semiconductor devices. Generally, the increase of temperature in semiconductor devices reduces the bandgap (E g ) of the semiconductor [5,6], and this variation due to the temperature change strongly affects the characteristics of semiconductor devices. Especially, the temperature influences the efficiency of the solar cell. Thus, understanding of temperature dependency is essential in order to broaden the field of application of solar cells.In this Letter, the characteristics of the CIGS solar cell with change in device temperature are investigated in terms of direct current (DC) and alternating current (AC) equivalent circuit model. First, we measured the properties of a CIGS solar cell with device temperature change at the illumination of one sun condition (AM 1.5), and CIGS solar cell parameters were evaluated using J-V and C-V analyses. From the analyses, the main factors that affect the conversion efficiency of the CIGS solar cell due to the temperature change are extracted.

Descriptive analysis of viability of fuel saving in commercial aircraft through the application of photovoltaic cells

“…The system loss factor, f SL , adopted is 1.2. As above mentioned, when the operating temperature increases the efficiency of the cells decreases [92,93]. This thermal behavior of PV cells is positive for solar aircrafts, due to the operating temperature.…”