Opportunities of copper addition in CH3NH3PbI3 perovskite and their photovoltaic performance evaluation

Perovskite solar cells (PSCs) have encountered a fulgurant development in their power-conversion efficiency (PCEs) generation in the drive to provide a facile, cheap and clean source of energy over just a few years. The most efficient PSCs are fabricated using CH3NH3PbI3 (MAPbI3) perovskite. However, being a promising photovoltaic (PV) performance piloted by MAPbI3, Pb-toxicity and poor stability obstructs the progress of PSCs in PV technology. In this regard, replacing Pb with some environmentally friendly, cheaper, and similar optoelectronic behaviour related alternative material or element is highly desirable. In this work, an attempt was made on copper as Cu (I) addition in the perovskite, MAPbI3 through some exotic ways in an intention of Pb replacement, i.e., complete Pb replacement with Cu, which generates MACuxI3 (1 ≤ x ≥ 2); partial lead replacement, i.e., MAPb1−xCuxI3; and cocktail perovskite, i.e., both MAPbI3 and MACuxI3 mixture, and finally they are employed for carbon-based perovskite solar cells. Remarkably, Cu incorporation facilitates the near-infrared (NIR) absorption, indicating a maximum solar spectrum absorbance. Integration of Cu as MAPb1−xCuxI3 results in the maximum PCE of ~12.85%, whereas using 1:1 cocktail perovskite solution of MAPbI3 and MACuxI3 exhibits an average PCE of ~12.43%. On the other hand, during complete Pb substituted perovskites, MACuxI3, the device has only experienced an average PCE of ~4.0%. However, MACuxI3-based PSCs lead to negligible PCE degradation as perceived up to 1000 h, whereas Pb-based other devices are experienced rapid PCE depletion over the same period. Noticeably, Cu-incorporation facilitates a comparatively steeper and lesser PCE degradation rate than Pb-based PSCs. These results may help exploit unlimited possibilities of the potential application of Pb-free based highly stable solar cells and highlights the opportunities for broad solar absorption towards the NIR route and enhanced device stability. Besides, Cu employment has the advantages of environmentally benign impact, earth abundance, good thermal and aqueous stability