Investigation of Internal Electric Fields in GaAs Solar Cell under Highly-concentrated Light

The temperature and the excitation-intensity dependences of the junction electric fields in the GaAs p-i-n solar cell structure have been investigated by using photoreflectance (PR) spectroscopy. In the p-i-n solar cell structure, two different electric fields are observed. The fast Fourier transform (FFT) analysis implies that the two electric fields can be assigned to the p-i and the i-n interfaces. The strengths of the electric fields at the p-i and the i-n interfaces are 38 and 44 kV/cm, respectively. The electric fields gradually increase due to the temperature-dependent photovoltage effect with increasing sample temperature. With increasing excitation intensity, the electric field at the p-i interface gradually decreases due to the photovoltage effect caused by carrier screening while that at the i-n interface is insensitive to the light's intensity. This abnormal behavior can be explained by the anisotropy carrier dynamics at the p-i and the i-n interfaces., The relation between the open-circuit voltage (Voc) and the ideality factor in concentration photovoltaic (CPV) devices is discussed.