organic semiconductors have been developed to absorb light into the near infrared region. [8] The gain in spectral coverage and short-circuit current density (J SC ) in the cells is, however, counteracted by an unavoidable loss in the open-circuit voltage (V OC ) when the bandgap decreases. [9] Given the intrinsic limits of singlejunction organic solar cells, there has been an increasing interest to develop multijunction architectures. [10] This paves the way to efficient solar cells by an improved utilization of photon energy. In a multijunction solar cell sunlight is spectrally distributed over two, or more subcells such that highenergy photons are absorbed in a wide bandgap subcell and low-energy photons in a small bandgap subcell. This reduces the thermalization losses for high-energy photons and the transmission losses for the low-energy photons. Most studies have focused on the tandem architecture, in which identical or different absorber layers are used, resulting in maximum efficiencies in the range of 10-13%. [11][12][13][14][15][16][17][18][19][20][21][22] At least conceptually, stacking three absorber layers in a triple-junction solar cell can lead to a further increase in efficiency. There are few examples of triple-junction organic solar cells. [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] The gain in efficiency achieved by these triple-junction devices was not always accompanied by a critical analysis of the measured performance. In a recent publication, Timmreck et al. methodically analyzed the literature on tandem organic solar cells, shedding light on the fact that the vast majority of the publications on organic tandem cells lacked a proper characterization. [42] Although the paper focused attention on the tandem structure, the argumentations provided can reasonably be extended to the case of triple-junctions. At present, the characterization of organic triple-junctions is often limited to measuring the J−V characteristics under simulated solar radiation and determining the external quantum efficiency (EQE) using different light sources to optically bias the subcells. [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] Nevertheless, organic materials commonly employed for solar cells feature peculiar characteristics that necessitate special attention for their EQE measurement. [42][43][44] An accurate analysis of the effect of bias light and bias voltage on the EQE of triple-junction organic solar cells is necessary.Detailed protocols for the characterization of triple-junction solar cells are available in the literature. [45] For many inorganic triple-junction solar cells the effect of bias voltage on the spectral response is very small, which makes correction for bias voltage not critical. [45] The aim of this work is to provide a characterization protocol for organic triple-junction solar cells that take into account the uniqueness of these particular materials. In order to do so, we combine optical and electrical modeling, use