Organic <i>p-i-n</i> diodes enable the development of highly efficient organic devices such as organic light-emitting diodes. Understanding charge carrier trapping in these diodes is essential to comprehensively describe their electrical behaviors and increase their efficiency further. Here, a new bias stress protocol is developed to study charge trapping and the influence of trapping on molecular doping in organic <i>p-i-n</i> diodes. The results are discussed with the help of a novel analytical model, which is capable of quantifying the density of trapped charges and the doping efficiency from capacitance spectroscopy. We propose that this combined experimental/modeling approach is versatile and can lead to an advanced understanding of trapping in organic electronic devices.