Stability study of large‐area perovskite solar cells fabricated with copper as low‐cost metal contact
Manas R. Samantaray, Naba Kr. Rana, Arun Kumar, Dhriti Sundar Ghosh, Nikhil Chander
Abstract
Perovskite solar cells (PSCs) have emerged as a promising technology for next-generation photovoltaic devices because of their ease of fabrication and high power conversion efficiency (PCE). The main obstacle that limits the commercialization of large-area PSCs is the lack of suitable solution-processable low-temperature fabrication methods and the perovskite material's chemical stability. With an increase in the active area of the cell, the defect states and the series resistance of the device increase, which is undesirable. We have demonstrated a repeatable fabrication method of small (0.25 cm2) and large (2.0 cm2) active area devices with Au and Cu as back contact electrodes. Small area perovskite devices with Cu and Au contact electrodes showed a PCE of 9.87% and 10.42%, respectively. When scaled up to 2.0 cm2, the devices showed a minor drop in the open-circuit voltage, but a significant decrease in photocurrent was observed. Large-area PSCs with Cu and Au contacts displayed a PCE of 5.61% and 5.92%, respectively. External quantum efficiency measurements at four different points provided similar results, thus confirming the uniformity of large-area devices. The stability of large-area devices under ambient environment conditions was tested for more than 7 weeks. Gold-based PSC retained almost 75% of its initial PCE when stored in ambient conditions for 50 days, whereas Cu-based devices showed a significant decrease in efficiency in the same period. Degradation in efficiency of PSCs occurred primarily due to the loss in photocurrent arising from active layer degradation. Simulations of perovskite devices carried out using Solar Cell Capacitance Simulator (SCAPS)-1D software also showed that similar efficiencies of PSCs may be obtained using Cu, instead of Au, as the low-cost metal contact. Novelty Statement Large-area perovskite solar cells (PSCs) based on gold and copper metal contacts have been fabricated, and copper contacts provide efficiencies comparable with the values obtained with gold contacts. The study shows that copper can be used as a low-cost alternative to gold to fabricate large-area, high-efficiency PSCs. Stability testing under ambient conditions has been carried out for 50 days to compare the performance of gold- and copper-based large-area PSCs.