Perovskite/polymer monolithic hybrid tandem solar cells utilizing a low-temperature, full solution process

In the current study, a monolithic integration of perovskite and polymer subcells into a tandem structure is realized through a full solution process. The wide bandgap perovskite absorber (CH3NH3PbI3) is processed via a one-step deposition employing an additive-assisted solvent wash method. In particular, a small molecule additive, BmPyPhB, is added into the precursor solution to improve the uniformity of the initial nucleation process of the crystal by providing heterogeneous nucleation sites throughout the solution space. Next, a solvent wash method is employed to induce the fast crystallization of uniform and well-defined grains in the absorber layer as well as to reduce the requirement for thermal annealing. Thus, the highest power conversion efficiency (PCE) of 9.1% is obtained for a single junction, planar-structured CH3NH3PbI3 solar cell. For the polymer absorber, a new IR-sensitive block copolymer, PBSeDTEG8, with photosensitivity up to 950 nm is utilized to broaden the photo-response of the tandem solar cell. More importantly, this polymer: PCBM blend exhibits improved thermal stability, which can endure thermal annealing process while fabricating the perovskite subcell. Subsequently, this hybrid tandem solar cell based on perovskite/polymer subcells achieves the highest efficiency of 10.2%.