Systematic electrical characterization study of a hybrid organic-inorganic semiconductor heterojunction at different illumination conditions

Electrical characterization study of hybrid heterojunctions (HHJs) based on CdS and poly(3octylthiophene) (P3OT) is performed in order to know the process repeatability and materials homogeneity that may influence on power conversion efficiency (PCE) of CdS/P3OT photovoltaic (PV) solar cells. Basic statistical and numerical techniques for solving linear equations were used for systematic analysis of PV performance of those HJs. Adjustment curves were calculated from experimental data with the adjustment factor equal to almost 99.9%, which means that the model has a high confidence level. They also were combined with theoretical models to establish a mathematical model that can describe the electrical performance of the mentioned junctions. PV response was analyzed under different illumination conditions, 23, 40, 124 and 285 mW/cm(2) of I-rr level. The relationships between short circuit current (J(SC)) and open circuit voltage (V-OC) with irradiance level (I-rr) were determined with high confidence level too. The dependence of J(SC) on I-rr is linear, whereas V-OC depends logarithmically on I-rr and on J(SC). For spectral response a 100 Watts halogen lamp and light filters from 400 nm to 689 nm of wavelength were used. The maximum incident photon converted to electron efficiency (IPCE) was experimentally determined at 2.75 eV of photon energy. This value corresponds to the optical forbidden gap of the inorganic semiconductor material. The obtained results are in agreement with the theoretical concepts of PV devices.