Optical simulation and experimental determination of the effect of subcell sequence in tetraphenyldibenzoperiflanthene‐ and phthalocyanine‐based tandem solar cells

In this work, series‐connected double‐junction tandem solar cells were fabricated by employing the complementary absorbing donors of tetraphenyldibenzoperiflanthene (DBP) and chloroaluminum phthalocyanine (ClAlPc). The tandem cell shows a high open circuit voltage of 1.57 V, summing those of single cells. The optical simulation and experimental results both demonstrate that the subcell (SC) sequence plays an important role in photocurrent and fill factor for tandem cells. It is helpful for current matching to use ClAlPc as a donor in the bottom SC for the ClAlPc‐DBP system, because the power conversion efficiency (η_PCE) is increased by 7% in the ClAlPc‐DBP normal tandem cell relative to the DBP‐ClAlPc reverse tandem cell. The simulated external quantum efficiency (EQE) spectra of the SCs in the DBP‐ClAlPc reverse cell overlap with each other thus resulting in a current mismatch. Via optical modeling, an optimized ClAlPc‐DBP normal tandem cell exhibits aη_PCEof 3.24% by slightly tuning layer thickness.