Towards modelling realistic ageing rates of amorphous silicon devices in operational environments

This paper presents a method to de-convolute the annealing and degradation processes of amorphous silicon devices. This will allow modelling realistic outdoor operation. Six devices underwent 14000 hours indoor light exposure at different and varying thermal conditions. The devices are exposed to light at variable temperatures between 25ºC and 85ºC under illumination as well as annealed in the dark. The temperature set-points were altered several times during the test to gain insights on how the balance between light induced degradation and thermal annealing is shifted. Measurements show that the degradation level is largely determined by the device’s operating temperature and both processes balance themselves out without consideration of device history. This is explained by the proposed modelling approach based on the defect pool model. The key parameters in the proposed modelling approach are the effective activation energies for degradation and annealing.