New Physical Deposition Approach for Low Cost Inorganic Hole Transport Layer in Normal Architecture of Durable Perovskite Solar Cells

Abstract

In this work we reported sputter deposited NiOx/Ni double layer as an HTM/contact couple in normal architecture of perovskite solar cell. A perovskite solar cell that is durable for more than 60 days was achieved, with increasing efficiency from 1.3% to 7.28% within 6 days. Moreover, low temperature direct deposition of NiOx layer on perovskite layer was introduced as a potential hole transport material for an efficient cost-effective solar cell applicable for various morphologies of perovskite layers, even for perovskite layers containing pinholes, which is a notable challenge in perovskite solar cells. The angular deposition of NiOx layers by dc reactive magnetron sputtering showed uniform and crack-free coverage of the perovskite layer with no negative impact on perovskite structure that is suitable for nickel back contact layer, surface shielding against moisture, and mechanical damages. Replacing the expensive complex materials in previous perovskite solar cells with low cost available materials introduces cost-effective scalable perovskite solar cells.

Formation and Diffusion of Metal Impurities in Perovskite Solar Cell Material CH3NH3PbI3: Implications on Solar Cell Degradation and Choice of Electrode

“…Ni, Co, and Pd have work functions close to that of Au and their Fermi levels are slightly above the VBM and below the Fermi level of MAPbI 3 ; thus, they may be very effective in hole extraction from MAPbI 3 or HTM through Ohmic contact. The Ni electrode has been used in MAPbI 3 solar cells38, 39, 53 whereas the Co and Pd electrodes have not been reported according to the best of our knowledge. The PCEs of 12.1853 and 10.4%38 have been reported for the solar cells with the common TiO 2 /MAPbI 3 /HTM/Ni device architecture.…”

“…Another factor affecting the choice of the metal electrode is electrical resistivity, which should be as low as possible to reduce the series resistance of the solar cell. Among the metals studied here, Au and Ag are the most widely used electrodes in MAPbI 3 solar cells while Cu, Cr, Mo, W, and Ni electrodes have also been reported 37, 38, 39, 49, 50, 51, 52, 53. We are not aware of the use of Co or Pd electrode in MAPbI 3 solar cells.…”

“…The unintentional impurity incorporation in MAPbI 3 could lead to significant device degradation. Many noble and transition metals (e.g., Au, Ag, Cu, Cr, Mo, Ni) have been used as electrodes in MAPbI 3 solar cells,31, 32, 33, 34, 35, 36, 37, 38, 39 which are potential sources of impurity contamination for the MAPbI 3 light absorption layer. The large dielectric constant in MAPbI 3 should promote the formation and diffusion of not only native defects but also impurities.…”

Research Update: Strategies for improving the stability of perovskite solar cells

“…A range of inorganic hole-transporter materials were proposed with the aim of improving the device stability, including copper thiocyanate (CuSCN), [34][35][36][37][38][39][40][41] copper iodide (CuI), 42,43 and nickel oxide (NiO x ). 44 The latter for example showed good stability over 60 days, during which control devices with spiro-OMeTAD underwent rapid degradation. 44 Evidently, next to high power-conversion efficiencies and a simple synthesis, the aspect of stability has become an important benchmark for new hole-transporter systems.…”

“…44 The latter for example showed good stability over 60 days, during which control devices with spiro-OMeTAD underwent rapid degradation. 44 Evidently, next to high power-conversion efficiencies and a simple synthesis, the aspect of stability has become an important benchmark for new hole-transporter systems. 45 In numerous publications, beneficial properties of hole-transporter have been claimed; however, a majority of those studies relies on "cupboard aging" or "shelf-live assessment," where devices are stored in a dark and often dry environment, and tested at different time points.…”