Air Environment Degradation of a High-Performance Inverted PTB7-Th:PC₇₀BM Solar Cell

Abstract

In this paper, the degradation of the electrical parameters of a high-performance inverted PTB7-Th:PC <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">70</sub> BM solar cell, having an efficiency of 10.95%, is analyzed. The cathode side is formed by indium tin oxide (ITO) material in contact with 10 nm of Poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)alt-2,7-(9,9-dioctylfluorene) (PFN) and 0.6 nm of lithium fluoride. The anode side is formed by V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> (hole-transport layer) in contact with Ag metal. The current density-voltage (J-V) curves, as well as the short-circuit current (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SC</sub> ), open-circuit voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OC</sub> ), fill factor, and power conversion efficiency parameters, were obtained from fabricated inverted organic solar cells (OSCs). The degradation of these parameters was measured as a function of time when the devices were exposed to an air environment. A metal-insulator-metal model was implemented using the device simulator Silvaco/ATLAS technology computer-aided design (TCAD) to simulate the degradation of the cells. The experimental and simulated J-V curves show good agreement on the fourth quadrant. To verify our model, a second structure was fabricated (ITO/PFN/PTB7:PC <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">70</sub> BM/V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> /Ag) and the experimental results were successfully fitted, which indicated that the proposed procedure can be used to predict the degradation behavior of an inverted OSC when it is exposed to ambient air.