High-performance parallel tandem MoTe/perovskite solar cell based on reduced graphene oxide as hole transport layer.

Recently, the impressive achievements accomplished in multijunction (tandem) perovskite solar cells have triggered a huge research effort to boost their performance. Here, using a three-dimensional (3D) finite element method (FEM) technique, we propose and investigate a parallel tandem PSCs consisting of two absorbing layers of MoTe and CHNHPbI with cascaded bandgaps to more efficiently use the near-infrared (NIR) solar spectrum. Endowed with a bandgap of about 1 eV, the MoTe layer in conjunction with a CHNHPbI layer is able to broaden the light absorption range of structure beyond the wavelength of 800 nm, up to 1200 nm. In addition to this, the MoTe material can not only appreciably harvest light even with a thickness as low as 20 nm due to their high absorption coefficient, but also make a perfect band alignment with the CHNHPbI layer. As a result, the proposed multijunction PCS yields a high power conversion efficiency (PCE) of 18.52% with a V of 0.83 V, J of 26.25 mA/cm, and FF of 0.84, which is considerably greater than its corresponding single-junction PSCs with PCE, V, J, and FF of, 14.01%, 1.14 V, 15.20 mA/cm, and 0.81, respectively. Furthermore, to mitigate the V loss caused by the low bandgap of MoTe, we demonstrate an increase in V from 0.84 to 0.928 V and in PCE from 18.52% to 20.32%, when we replace a reduced graphene oxide (rGO) layer with Spiro-OMeTAD layer as a hole transport layer (HTL).